[PATCH xserver 3/5] dmx/doc: resolve conflict between generated files also in git
Gaetan Nadon
memsize at videotron.ca
Sat Feb 6 06:37:08 PST 2010
dmx.txt and scaled.txt are both generated and in git.
The version in git is renamed to .text which avoids
the following problems:
accidently deleting the file when it is cleaned by makefile
accidently checking-in the file when it is generated
git refusing to rebase due to directory not clean
possibly breaking automated builds
Signed-off-by: Gaetan Nadon <memsize at videotron.ca>
---
hw/dmx/doc/Makefile.am | 4 +-
hw/dmx/doc/dmx.text | 2989 ++++++++++++++++++++++++++++++++++++++++++++++++
hw/dmx/doc/dmx.txt | 2989 ------------------------------------------------
hw/dmx/doc/scaled.text | 579 ++++++++++
hw/dmx/doc/scaled.txt | 579 ----------
5 files changed, 3570 insertions(+), 3570 deletions(-)
create mode 100644 hw/dmx/doc/dmx.text
delete mode 100644 hw/dmx/doc/dmx.txt
create mode 100644 hw/dmx/doc/scaled.text
delete mode 100644 hw/dmx/doc/scaled.txt
diff --git a/hw/dmx/doc/Makefile.am b/hw/dmx/doc/Makefile.am
index ac18b64..048b6b2 100644
--- a/hw/dmx/doc/Makefile.am
+++ b/hw/dmx/doc/Makefile.am
@@ -74,12 +74,12 @@ EXTRA_DIST = \
$(SGML_FILES) \
DMXSpec.txt \
DMXSpec-v1.txt \
- dmx.txt \
+ dmx.text \
doxygen.conf \
doxygen.css \
doxygen.foot \
doxygen.head \
- scaled.txt \
+ scaled.text \
html/annotated.html \
html/ChkNotMaskEv_8c.html \
html/ChkNotMaskEv_8h.html \
diff --git a/hw/dmx/doc/dmx.text b/hw/dmx/doc/dmx.text
new file mode 100644
index 0000000..568c751
--- /dev/null
+++ b/hw/dmx/doc/dmx.text
@@ -0,0 +1,2989 @@
+ Distributed Multihead X design
+ Kevin E. Martin, David H. Dawes, and Rickard E. Faith
+
+ 29 June 2004 (created 25 July 2001)
+
+ This document covers the motivation, background, design, and implemen-
+ tation of the distributed multihead X (DMX) system. It is a living
+ document and describes the current design and implementation details
+ of the DMX system. As the project progresses, this document will be
+ continually updated to reflect the changes in the code and/or design.
+ _C_o_p_y_r_i_g_h_t _2_0_0_1 _b_y _V_A _L_i_n_u_x _S_y_s_t_e_m_s_, _I_n_c_._, _F_r_e_m_o_n_t_, _C_a_l_i_f_o_r_n_i_a_. _C_o_p_y_-
+ _r_i_g_h_t _2_0_0_1_-_2_0_0_4 _b_y _R_e_d _H_a_t_, _I_n_c_._, _R_a_l_e_i_g_h_, _N_o_r_t_h _C_a_r_o_l_i_n_a
+
+ ______________________________________________________________________
+
+ Table of Contents
+
+
+
+ 1. Introduction
+ 1.1 The Distributed Multihead X Server
+ 1.2 Layout of Paper
+
+ 2. Development plan
+ 2.1 Bootstrap code
+ 2.2 Input device handling
+ 2.3 Output device handling
+ 2.3.1 Initialization
+ 2.3.2 Handling rendering requests
+ 2.4 Optimizing DMX
+ 2.5 DMX X extension support
+ 2.6 Common X extension support
+ 2.7 OpenGL support
+
+ 3. Current issues
+ 3.1 Fonts
+ 3.2 Zero width rendering primitives
+ 3.3 Output scaling
+ 3.4 Per-screen colormaps
+
+ A. Background
+ A.1 Core input device handling
+ A.1.1 InitInput()
+ A.1.2 InitAndStartDevices()
+ A.1.3 devReadInput()
+ A.1.4 ProcessInputEvents()
+ A.1.5 DisableDevice()
+ A.1.6 CloseDevice()
+ A.1.7 LegalModifier()
+ A.2 Output handling
+ A.2.1 InitOutput()
+ A.2.2 AddScreen()
+ A.2.3 ScreenInit()
+ A.2.4 CloseScreen()
+ A.2.5 GC operations
+ A.2.6 Xnest
+ A.2.7 Shadow framebuffer
+ A.3 Xinerama
+ A.3.1 Xinerama-specific changes to the DIX code
+ A.3.2 Xinerama-specific changes to the MI code
+ A.3.3 Intercepted DIX core requests
+
+ B. Development Results
+ B.1 Phase I
+ B.1.1 Scope
+ B.1.2 Results
+ B.1.3 X Test Suite
+ B.1.3.1 Introduction
+ B.1.3.2 Expected Failures for a Single Head
+ B.1.3.3 Expected Failures for Xinerama
+ B.1.3.4 Additional Failures from Xdmx
+ B.1.3.5 Summary and Future Work
+ B.1.4 Fonts
+ B.1.5 Performance
+ B.1.6 Pixmaps
+ B.2 Phase II
+ B.2.1 Moving from XFree86 4.1.99.1 to 4.2.0.0
+ B.2.2 Global changes
+ B.2.3 XSync() Batching
+ B.2.4 Offscreen Optimization
+ B.2.5 Lazy Window Creation Optimization
+ B.2.6 Subdividing Rendering Primitives
+ B.2.7 Summary of x11perf Data
+ B.2.8 Profiling with OProfile
+ B.2.9 X Test Suite
+ B.3 Phase III
+ B.3.1 SHAPE
+ B.3.2 RENDER
+ B.3.3 XKEYBOARD
+ B.3.4 XInput
+ B.3.5 DPMS
+ B.3.6 Other Extensions
+ B.4 Phase IV
+ B.4.1 Moving to XFree86 4.3.0
+ B.4.2 Extensions
+ B.4.2.1 XC-MISC (supported)
+ B.4.2.2 Extended-Visual-Information (supported)
+ B.4.2.3 RES (supported)
+ B.4.2.4 BIG-REQUESTS (supported)
+ B.4.2.5 XSYNC (supported)
+ B.4.2.6 XTEST, RECORD, DEC-XTRAP (supported) and XTestExtension1 (not supported)
+ B.4.2.7 MIT-MISC (not supported)
+ B.4.2.8 SCREENSAVER (not supported)
+ B.4.2.9 GLX (supported)
+ B.4.2.10 RENDER (supported)
+ B.4.2.11 Summary
+ B.4.3 Additional Testing with the X Test Suite
+ B.4.3.1 XFree86 without XTEST
+ B.4.3.2 XFree86 with XTEST
+ B.4.3.3 Xdmx with XTEST, without Xinerama, without GLX
+ B.4.3.4 Xdmx with XTEST, with Xinerama, without GLX
+ B.4.3.5 Xdmx with XTEST, with Xinerama, with GLX
+ B.4.3.6 Conclusion
+ B.4.4 Dynamic Reconfiguration
+ B.4.4.1 Dynamic reconfiguration extension
+ B.4.4.2 Bounding box
+ B.4.4.3 Sample applications
+ B.4.4.4 Additional notes
+ B.4.5 Doxygen documentation
+ B.4.6 Valgrind
+ B.4.7 RATS
+
+
+ ______________________________________________________________________
+
+ 11.. IInnttrroodduuccttiioonn
+
+ 11..11.. TThhee DDiissttrriibbuutteedd MMuullttiihheeaadd XX SSeerrvveerr
+
+ Current Open Source multihead solutions are limited to a single
+ physical machine. A single X server controls multiple display
+ devices, which can be arranged as independent heads or unified into a
+ single desktop (with Xinerama). These solutions are limited to the
+ number of physical devices that can co-exist in a single machine
+ (e.g., due to the number of AGP/PCI slots available for graphics
+ cards). Thus, large tiled displays are not currently possible. The
+ work described in this paper will eliminate the requirement that the
+ display devices reside in the same physical machine. This will be
+ accomplished by developing a front-end proxy X server that will
+ control multiple back-end X servers that make up the large display.
+
+
+ The overall structure of the distributed multihead X (DMX) project is
+ as follows: A single front-end X server will act as a proxy to a set
+ of back-end X servers, which handle all of the visible rendering. X
+ clients will connect to the front-end server just as they normally
+ would to a regular X server. The front-end server will present an
+ abstracted view to the client of a single large display. This will
+ ensure that all standard X clients will continue to operate without
+ modification (limited, as always, by the visuals and extensions
+ provided by the X server). Clients that are DMX-aware will be able to
+ use an extension to obtain information about the back-end servers
+ (e.g., for placement of pop-up windows, window alignments by the
+ window manager, etc.).
+
+
+ The architecture of the DMX server is divided into two main sections:
+ input (e.g., mouse and keyboard events) and output (e.g., rendering
+ and windowing requests). Each of these are describe briefly below,
+ and the rest of this design document will describe them in greater
+ detail.
+
+
+ The DMX server can receive input from three general types of input
+ devices: "local" devices that are physically attached to the machine
+ on which DMX is running, "backend" devices that are physically
+ attached to one or more of the back-end X servers (and that generate
+ events via the X protocol stream from the backend), and "console"
+ devices that can be abstracted from any non-back-end X server.
+ Backend and console devices are treated differently because the
+ pointer device on the back-end X server also controls the location of
+ the hardware X cursor. Full support for XInput extension devices is
+ provided.
+
+
+ Rendering requests will be accepted by the front-end server; however,
+ rendering to visible windows will be broken down as needed and sent to
+ the appropriate back-end server(s) via X11 library calls for actual
+ rendering. The basic framework will follow a Xnest-style approach.
+ GC state will be managed in the front-end server and sent to the
+ appropriate back-end server(s) as required. Pixmap rendering will (at
+ least initially) be handled by the front-end X server. Windowing
+ requests (e.g., ordering, mapping, moving, etc.) will handled in the
+ front-end server. If the request requires a visible change, the
+ windowing operation will be translated into requests for the
+ appropriate back-end server(s). Window state will be mirrored in the
+ back-end server(s) as needed.
+
+
+ 11..22.. LLaayyoouutt ooff PPaappeerr
+
+ The next section describes the general development plan that was
+ actually used for implementation. The final section discusses
+ outstanding issues at the conclusion of development. The first
+ appendix provides low-level technical detail that may be of interest
+ to those intimately familiar with the X server architecture. The
+ final appendix describes the four phases of development that were
+ performed during the first two years of development.
+
+
+ The final year of work was divided into 9 tasks that are not described
+ in specific sections of this document. The major tasks during that
+ time were the enhancement of the reconfiguration ability added in
+ Phase IV, addition of support for a dynamic number of back-end
+ displays (instead of a hard-coded limit), and the support for back-end
+ display and input removal and addition. This work is mentioned in
+ this paper, but is not covered in detail.
+
+
+ 22.. DDeevveellooppmmeenntt ppllaann
+
+ This section describes the development plan from approximately June
+ 2001 through July 2003.
+
+
+
+ 22..11.. BBoooottssttrraapp ccooddee
+
+ To allow for rapid development of the DMX server by multiple
+ developers during the first development stage, the problem will be
+ broken down into three tasks: the overall DMX framework, back-end
+ rendering services and input device handling services. However,
+ before the work begins on these tasks, a simple framework that each
+ developer could use was implemented to bootstrap the development
+ effort. This framework renders to a single back-end server and
+ provides dummy input devices (i.e., the keyboard and mouse). The
+ simple back-end rendering service was implemented using the shadow
+ framebuffer support currently available in the XFree86 environment.
+
+
+ Using this bootstrapping framework, each developer has been able to
+ work on each of the tasks listed above independently as follows: the
+ framework will be extended to handle arbitrary back-end server
+ configurations; the back-end rendering services will be transitioned
+ to the more efficient Xnest-style implementation; and, an input device
+ framework to handle various input devices via the input extension will
+ be developed.
+
+
+ Status: The boot strap code is complete.
+
+
+
+ 22..22.. IInnppuutt ddeevviiccee hhaannddlliinngg
+
+ An X server (including the front-end X server) requires two core input
+ devices -- a keyboard and a pointer (mouse). These core devices are
+ handled and required by the core X11 protocol. Additional types of
+ input devices may be attached and utilized via the XInput extension.
+ These are usually referred to as ``XInput extension devices'',
+
+
+ There are some options as to how the front-end X server gets its core
+ input devices:
+
+
+ 1. Local Input. The physical input devices (e.g., keyboard and mouse)
+ can be attached directly to the front-end X server. In this case,
+ the keyboard and mouse on the machine running the front-end X
+ server will be used. The front-end will have drivers to read the
+ raw input from those devices and convert it into the required X
+ input events (e.g., key press/release, pointer button
+ press/release, pointer motion). The front-end keyboard driver will
+ keep track of keyboard properties such as key and modifier
+ mappings, autorepeat state, keyboard sound and led state.
+ Similarly the front-end pointer driver will keep track if pointer
+ properties such as the button mapping and movement acceleration
+ parameters. With this option, input is handled fully in the front-
+ end X server, and the back-end X servers are used in a display-only
+ mode. This option was implemented and works for a limited number
+ of Linux-specific devices. Adding additional local input devices
+ for other architectures is expected to be relatively simple.
+
+
+ The following options are available for implementing local input
+ devices:
+
+
+ a. The XFree86 X server has modular input drivers that could be
+ adapted for this purpose. The mouse driver supports a wide
+ range of mouse types and interfaces, as well as a range of
+ Operating System platforms. The keyboard driver in XFree86 is
+ not currently as modular as the mouse driver, but could be made
+ so. The XFree86 X server also has a range of other input
+ drivers for extended input devices such as tablets and touch
+ screens. Unfortunately, the XFree86 drivers are generally
+ complex, often simultaneously providing support for multiple
+ devices across multiple architectures; and rely so heavily on
+ XFree86-specific helper-functions, that this option was not
+ pursued.
+
+
+ b. The kdrive X server in XFree86 has built-in drivers that support
+ PS/2 mice and keyboard under Linux. The mouse driver can
+ indirectly handle other mouse types if the Linux utility gpm is
+ used as to translate the native mouse protocol into PS/2 mouse
+ format. These drivers could be adapted and built in to the
+ front-end X server if this range of hardware and OS support is
+ sufficient. While much simpler than the XFree86 drivers, the
+ kdrive drivers were not used for the DMX implementation.
+
+ c. Reimplementation of keyboard and mouse drivers from scratch for
+ the DMX framework. Because keyboard and mouse drivers are
+ relatively trivial to implement, this pathway was selected.
+ Other drivers in the X source tree were referenced, and
+ significant contributions from other drivers are noted in the
+ DMX source code.
+
+
+ 2. Backend Input. The front-end can make use of the core input
+ devices attached to one or more of the back-end X servers. Core
+ input events from multiple back-ends are merged into a single input
+ event stream. This can work sanely when only a single set of input
+ devices is used at any given time. The keyboard and pointer state
+ will be handled in the front-end, with changes propagated to the
+ back-end servers as needed. This option was implemented and works
+ well. Because the core pointer on a back-end controls the hardware
+ mouse on that back-end, core pointers cannot be treated as XInput
+ extension devices. However, all back-end XInput extensions devices
+ can be mapped to either DMX core or DMX XInput extension devices.
+
+ 3. Console Input. The front-end server could create a console window
+ that is displayed on an X server independent of the back-end X
+ servers. This console window could display things like the
+ physical screen layout, and the front-end could get its core input
+ events from events delivered to the console window. This option
+ was implemented and works well. To help the human navigate, window
+ outlines are also displayed in the console window. Further,
+ console windows can be used as either core or XInput extension
+ devices.
+
+ 4. Other options were initially explored, but they were all partial
+ subsets of the options listed above and, hence, are irrelevant.
+
+
+ Although extended input devices are not specifically mentioned in the
+ Distributed X requirements, the options above were all implemented so
+ that XInput extension devices were supported.
+
+
+ The bootstrap code (Xdmx) had dummy input devices, and these are still
+ supported in the final version. These do the necessary initialization
+ to satisfy the X server's requirements for core pointer and keyboard
+ devices, but no input events are ever generated.
+
+
+ Status: The input code is complete. Because of the complexity of the
+ XFree86 input device drivers (and their heavy reliance on XFree86
+ infrastructure), separate low-level device drivers were implemented
+ for Xdmx. The following kinds of drivers are supported (in general,
+ the devices can be treated arbitrarily as "core" input devices or as
+ XInput "extension" devices; and multiple instances of different kinds
+ of devices can be simultaneously available):
+
+ 1. A "dummy" device drive that never generates events.
+
+ 2. "Local" input is from the low-level hardware on which the Xdmx
+ binary is running. This is the only area where using the XFree86
+ driver infrastructure would have been helpful, and then only
+ partially, since good support for generic USB devices does not yet
+ exist in XFree86 (in any case, XFree86 and kdrive driver code was
+ used where possible). Currently, the following local devices are
+ supported under Linux (porting to other operating systems should be
+ fairly straightforward):
+
+ +o Linux keyboard
+
+ +o Linux serial mouse (MS)
+
+ +o Linux PS/2 mouse
+
+ +o USB keyboard
+
+ +o USB mouse
+
+ +o USB generic device (e.g., joystick, gamepad, etc.)
+
+
+ 3. "Backend" input is taken from one or more of the back-end displays.
+ In this case, events are taken from the back-end X server and are
+ converted to Xdmx events. Care must be taken so that the sprite
+ moves properly on the display from which input is being taken.
+
+ 4. "Console" input is taken from an X window that Xdmx creates on the
+ operator's display (i.e., on the machine running the Xdmx binary).
+ When the operator's mouse is inside the console window, then those
+ events are converted to Xdmx events. Several special features are
+ available: the console can display outlines of windows that are on
+ the Xdmx display (to facilitate navigation), the cursor can be
+ confined to the console, and a "fine" mode can be activated to
+ allow very precise cursor positioning.
+
+
+
+ 22..33.. OOuuttppuutt ddeevviiccee hhaannddlliinngg
+
+ The output of the DMX system displays rendering and windowing requests
+ across multiple screens. The screens are typically arranged in a grid
+ such that together they represent a single large display.
+
+
+ The output section of the DMX code consists of two parts. The first
+ is in the front-end proxy X server (Xdmx), which accepts client
+ connections, manages the windows, and potentially renders primitives
+ but does not actually display any of the drawing primitives. The
+ second part is the back-end X server(s), which accept commands from
+ the front-end server and display the results on their screens.
+
+
+ 22..33..11.. IInniittiiaalliizzaattiioonn
+
+ The DMX front-end must first initialize its screens by connecting to
+ each of the back-end X servers and collecting information about each
+ of these screens. However, the information collected from the back-
+ end X servers might be inconsistent. Handling these cases can be
+ difficult and/or inefficient. For example, a two screen system has
+ one back-end X server running at 16bpp while the second is running at
+ 32bpp. Converting rendering requests (e.g., XPutImage() or
+ XGetImage() requests) to the appropriate bit depth can be very time
+ consuming. Analyzing these cases to determine how or even if it is
+ possible to handle them is required. The current Xinerama code
+ handles many of these cases (e.g., in PanoramiXConsolidate()) and will
+ be used as a starting point. In general, the best solution is to use
+ homogeneous X servers and display devices. Using back-end servers
+ with the same depth is a requirement of the final DMX implementation.
+
+
+ Once this screen consolidation is finished, the relative position of
+ each back-end X server's screen in the unified screen is initialized.
+ A full-screen window is opened on each of the back-end X servers, and
+ the cursor on each screen is turned off. The final DMX implementation
+ can also make use of a partial-screen window, or multiple windows per
+ back-end screen.
+
+
+ 22..33..22.. HHaannddlliinngg rreennddeerriinngg rreeqquueessttss
+
+ After initialization, X applications connect to the front-end server.
+ There are two possible implementations of how rendering and windowing
+ requests are handled in the DMX system:
+
+
+ 1. A shadow framebuffer is used in the front-end server as the render
+ target. In this option, all protocol requests are completely
+ handled in the front-end server. All state and resources are
+ maintained in the front-end including a shadow copy of the entire
+ framebuffer. The framebuffers attached to the back-end servers are
+ updated by XPutImage() calls with data taken directly from the
+ shadow framebuffer.
+
+
+ This solution suffers from two main problems. First, it does not
+ take advantage of any accelerated hardware available in the system.
+ Second, the size of the XPutImage() calls can be quite large and
+ thus will be limited by the bandwidth available.
+
+
+ The initial DMX implementation used a shadow framebuffer by
+ default.
+
+
+ 2. Rendering requests are sent to each back-end server for handling
+ (as is done in the Xnest server described above). In this option,
+ certain protocol requests are handled in the front-end server and
+ certain requests are repackaged and then sent to the back-end
+ servers. The framebuffer is distributed across the multiple back-
+ end servers. Rendering to the framebuffer is handled on each back-
+ end and can take advantage of any acceleration available on the
+ back-end servers' graphics display device. State is maintained
+ both in the front and back-end servers.
+
+
+ This solution suffers from two main drawbacks. First, protocol
+ requests are sent to all back-end servers -- even those that will
+ completely clip the rendering primitive -- which wastes bandwidth
+ and processing time. Second, state is maintained both in the
+ front- and back-end servers. These drawbacks are not as severe as
+ in option 1 (above) and can either be overcome through
+ optimizations or are acceptable. Therefore, this option will be
+ used in the final implementation.
+
+
+ The final DMX implementation defaults to this mechanism, but also
+ supports the shadow framebuffer mechanism. Several optimizations
+ were implemented to eliminate the drawbacks of the default
+ mechanism. These optimizations are described the section below and
+ in Phase II of the Development Results (see appendix).
+
+
+
+ Status: Both the shadow framebuffer and Xnest-style code is complete.
+
+
+
+ 22..44.. OOppttiimmiizziinngg DDMMXX
+
+ Initially, the Xnest-style solution's performance will be measured and
+ analyzed to determine where the performance bottlenecks exist. There
+ are four main areas that will be addressed.
+
+
+ First, to obtain reasonable interactivity with the first development
+ phase, XSync() was called after each protocol request. The XSync()
+ function flushes any pending protocol requests. It then waits for the
+ back-end to process the request and send a reply that the request has
+ completed. This happens with each back-end server and performance
+ greatly suffers. As a result of the way XSync() is called in the
+ first development phase, the batching that the X11 library performs is
+ effectively defeated. The XSync() call usage will be analyzed and
+ optimized by batching calls and performing them at regular intervals,
+ except where interactivity will suffer (e.g., on cursor movements).
+
+
+ Second, the initial Xnest-style solution described above sends the
+ repackaged protocol requests to all back-end servers regardless of
+ whether or not they would be completely clipped out. The requests
+ that are trivially rejected on the back-end server wastes the limited
+ bandwidth available. By tracking clipping changes in the DMX X
+ server's windowing code (e.g., by opening, closing, moving or resizing
+ windows), we can determine whether or not back-end windows are visible
+ so that trivial tests in the front-end server's GC ops drawing
+ functions can eliminate these unnecessary protocol requests.
+
+
+ Third, each protocol request will be analyzed to determine if it is
+ possible to break the request into smaller pieces at display
+ boundaries. The initial ones to be analyzed are put and get image
+ requests since they will require the greatest bandwidth to transmit
+ data between the front and back-end servers. Other protocol requests
+ will be analyzed and those that will benefit from breaking them into
+ smaller requests will be implemented.
+
+
+ Fourth, an extension is being considered that will allow font glyphs
+ to be transferred from the front-end DMX X server to each back-end
+ server. This extension will permit the front-end to handle all font
+ requests and eliminate the requirement that all back-end X servers
+ share the exact same fonts as the front-end server. We are
+ investigating the feasibility of this extension during this
+ development phase.
+
+
+ Other potential optimizations will be determined from the performance
+ analysis.
+
+ Please note that in our initial design, we proposed optimizing BLT
+ operations (e.g., XCopyArea() and window moves) by developing an
+ extension that would allow individual back-end servers to directly
+ copy pixel data to other back-end servers. This potential
+ optimization was in response to the simple image movement
+ implementation that required potentially many calls to GetImage() and
+ PutImage(). However, the current Xinerama implementation handles
+ these BLT operations differently. Instead of copying data to and from
+ screens, they generate expose events -- just as happens in the case
+ when a window is moved from off a screen to on screen. This approach
+ saves the limited bandwidth available between front and back-end
+ servers and is being standardized with Xinerama. It also eliminates
+ the potential setup problems and security issues resulting from having
+ each back-end server open connections to all other back-end servers.
+ Therefore, we suggest accepting Xinerama's expose event solution.
+
+
+ Also note that the approach proposed in the second and third
+ optimizations might cause backing store algorithms in the back-end to
+ be defeated, so a DMX X server configuration flag will be added to
+ disable these optimizations.
+
+
+ Status: The optimizations proposed above are complete. It was
+ determined that the using the xfs font server was sufficient and
+ creating a new mechanism to pass glyphs was redundant; therefore, the
+ fourth optimization proposed above was not included in DMX.
+
+
+
+ 22..55.. DDMMXX XX eexxtteennssiioonn ssuuppppoorrtt
+
+ The DMX X server keeps track of all the windowing information on the
+ back-end X servers, but does not currently export this information to
+ any client applications. An extension will be developed to pass the
+ screen information and back-end window IDs to DMX-aware clients.
+ These clients can then use this information to directly connect to and
+ render to the back-end windows. Bypassing the DMX X server allows
+ DMX-aware clients to break up complex rendering requests on their own
+ and send them directly to the windows on the back-end server's
+ screens. An example of a client that can make effective use of this
+ extension is Chromium.
+
+
+ Status: The extension, as implemented, is fully documented in "Client-
+ to-Server DMX Extension to the X Protocol". Future changes might be
+ required based on feedback and other proposed enhancements to DMX.
+ Currently, the following facilities are supported:
+
+ 1. Screen information (clipping rectangle for each screen relative to
+ the virtual screen)
+
+ 2. Window information (window IDs and clipping information for each
+ back-end window that corresponds to each DMX window)
+
+ 3. Input device information (mappings from DMX device IDs to back-end
+ device IDs)
+
+ 4. Force window creation (so that a client can override the server-
+ side lazy window creation optimization)
+
+ 5. Reconfiguration (so that a client can request that a screen
+ position be changed)
+
+ 6. Addition and removal of back-end servers and back-end and console
+ inputs.
+ 22..66.. CCoommmmoonn XX eexxtteennssiioonn ssuuppppoorrtt
+
+ The XInput, XKeyboard and Shape extensions are commonly used
+ extensions to the base X11 protocol. XInput allows multiple and non-
+ standard input devices to be accessed simultaneously. These input
+ devices can be connected to either the front-end or back-end servers.
+ XKeyboard allows much better keyboard mappings control. Shape adds
+ support for arbitrarily shaped windows and is used by various window
+ managers. Nearly all potential back-end X servers make these
+ extensions available, and support for each one will be added to the
+ DMX system.
+
+
+ In addition to the extensions listed above, support for the X
+ Rendering extension (Render) is being developed. Render adds digital
+ image composition to the rendering model used by the X Window System.
+ While this extension is still under development by Keith Packard of
+ HP, support for the current version will be added to the DMX system.
+
+
+ Support for the XTest extension was added during the first development
+ phase.
+
+
+ Status: The following extensions are supported and are discussed in
+ more detail in Phase IV of the Development Results (see appendix):
+ BIG-REQUESTS, DEC-XTRAP, DMX, DPMS, Extended-Visual-Information, GLX,
+ LBX, RECORD, RENDER, SECURITY, SHAPE, SYNC, X-Resource, XC-APPGROUP,
+ XC-MISC, XFree86-Bigfont, XINERAMA, XInputExtension, XKEYBOARD, and
+ XTEST.
+
+
+ 22..77.. OOppeennGGLL ssuuppppoorrtt
+
+ OpenGL support using the Mesa code base exists in XFree86 release 4
+ and later. Currently, the direct rendering infrastructure (DRI)
+ provides accelerated OpenGL support for local clients and
+ unaccelerated OpenGL support (i.e., software rendering) is provided
+ for non-local clients.
+
+
+ The single head OpenGL support in XFree86 4.x will be extended to use
+ the DMX system. When the front and back-end servers are on the same
+ physical hardware, it is possible to use the DRI to directly render to
+ the back-end servers. First, the existing DRI will be extended to
+ support multiple display heads, and then to support the DMX system.
+ OpenGL rendering requests will be direct rendering to each back-end X
+ server. The DRI will request the screen layout (either from the
+ existing Xinerama extension or a DMX-specific extension). Support for
+ synchronized swap buffers will also be added (on hardware that
+ supports it). Note that a single front-end server with a single back-
+ end server on the same physical machine can emulate accelerated
+ indirect rendering.
+
+
+ When the front and back-end servers are on different physical hardware
+ or are using non-XFree86 4.x X servers, a mechanism to render
+ primitives across the back-end servers will be provided. There are
+ several options as to how this can be implemented.
+
+
+ 1. The existing OpenGL support in each back-end server can be used by
+ repackaging rendering primitives and sending them to each back-end
+ server. This option is similar to the unoptimized Xnest-style
+ approach mentioned above. Optimization of this solution is beyond
+ the scope of this project and is better suited to other distributed
+ rendering systems.
+
+ 2. Rendering to a pixmap in the front-end server using the current
+ XFree86 4.x code, and then displaying to the back-ends via calls to
+ XPutImage() is another option. This option is similar to the
+ shadow frame buffer approach mentioned above. It is slower and
+ bandwidth intensive, but has the advantage that the back-end
+ servers are not required to have OpenGL support.
+
+
+ These, and other, options will be investigated in this phase of the
+ work.
+
+
+ Work by others have made Chromium DMX-aware. Chromium will use the
+ DMX X protocol extension to obtain information about the back-end
+ servers and will render directly to those servers, bypassing DMX.
+
+
+ Status: OpenGL support by the glxProxy extension was implemented by
+ SGI and has been integrated into the DMX code base.
+
+
+
+ 33.. CCuurrrreenntt iissssuueess
+
+ In this sections the current issues are outlined that require further
+ investigation.
+
+
+ 33..11.. FFoonnttss
+
+ The font path and glyphs need to be the same for the front-end and
+ each of the back-end servers. Font glyphs could be sent to the back-
+ end servers as necessary but this would consume a significant amount
+ of available bandwidth during font rendering for clients that use many
+ different fonts (e.g., Netscape). Initially, the font server (xfs)
+ will be used to provide the fonts to both the front-end and back-end
+ servers. Other possibilities will be investigated during development.
+
+
+ 33..22.. ZZeerroo wwiiddtthh rreennddeerriinngg pprriimmiittiivveess
+
+ To allow pixmap and on-screen rendering to be pixel perfect, all back-
+ end servers must render zero width primitives exactly the same as the
+ front-end renders the primitives to pixmaps. For those back-end
+ servers that do not exactly match, zero width primitives will be
+ automatically converted to one width primitives. This can be handled
+ in the front-end server via the GC state.
+
+
+ 33..33.. OOuuttppuutt ssccaalliinngg
+
+ With very large tiled displays, it might be difficult to read the
+ information on the standard X desktop. In particular, the cursor can
+ be easily lost and fonts could be difficult to read. Automatic
+ primitive scaling might prove to be very useful. We will investigate
+ the possibility of scaling the cursor and providing a set of alternate
+ pre-scaled fonts to replace the standard fonts that many applications
+ use (e.g., fixed). Other options for automatic scaling will also be
+ investigated.
+
+
+
+ 33..44.. PPeerr--ssccrreeeenn ccoolloorrmmaappss
+
+ Each screen's default colormap in the set of back-end X servers should
+ be able to be adjusted via a configuration utility. This support is
+ would allow the back-end screens to be calibrated via custom gamma
+ tables. On 24-bit systems that support a DirectColor visual, this
+ type of correction can be accommodated. One possible implementation
+ would be to advertise to X client of the DMX server a TrueColor visual
+ while using DirectColor visuals on the back-end servers to implement
+ this type of color correction. Other options will be investigated.
+
+
+ AA.. BBaacckkggrroouunndd
+
+ This section describes the existing Open Source architectures that can
+ be used to handle multiple screens and upon which this development
+ project is based. This section was written before the implementation
+ was finished, and may not reflect actual details of the
+ implementation. It is left for historical interest only.
+
+
+ AA..11.. CCoorree iinnppuutt ddeevviiccee hhaannddlliinngg
+
+ The following is a description of how core input devices are handled
+ by an X server.
+
+
+ AA..11..11.. IInniittIInnppuutt(())
+
+ InitInput() is a DDX function that is called at the start of each
+ server generation from the X server's main() function. Its purpose is
+ to determine what input devices are connected to the X server,
+ register them with the DIX and MI layers, and initialize the input
+ event queue. InitInput() does not have a return value, but the X
+ server will abort if either a core keyboard device or a core pointer
+ device are not registered. Extended input (XInput) devices can also
+ be registered in InitInput().
+
+
+ InitInput() usually has implementation specific code to determine
+ which input devices are available. For each input device it will be
+ using, it calls AddInputDevice():
+
+
+ AAddddIInnppuuttDDeevviiccee(())
+ This DIX function allocates the device structure, registers a
+ callback function (which handles device init, close, on and
+ off), and returns the input handle, which can be treated as
+ opaque. It is called once for each input device.
+
+
+ Once input handles for core keyboard and core pointer devices have
+ been obtained from AddInputDevice(), they are registered as core
+ devices by calling RegisterPointerDevice() and
+ RegisterKeyboardDevice(). Each of these should be called once. If
+ both core devices are not registered, then the X server will exit with
+ a fatal error when it attempts to start the input devices in
+ InitAndStartDevices(), which is called directly after InitInput() (see
+ below).
+
+
+ RReeggiisstteerr{{PPooiinntteerr,,KKeeyybbooaarrdd}}DDeevviiccee(())
+ These DIX functions take a handle returned from AddInputDevice()
+ and initialize the core input device fields in inputInfo, and
+ initialize the input processing and grab functions for each core
+ input device.
+ The core pointer device is then registered with the miPointer code
+ (which does the high level cursor handling). While this registration
+ is not necessary for correct miPointer operation in the current
+ XFree86 code, it is still done mostly for compatibility reasons.
+
+
+ mmiiRReeggiisstteerrPPooiinntteerrDDeevviiccee(())
+ This MI function registers the core pointer's input handle with
+ with the miPointer code.
+
+
+ The final part of InitInput() is the initialization of the input event
+ queue handling. In most cases, the event queue handling provided in
+ the MI layer is used. The primary XFree86 X server uses its own event
+ queue handling to support some special cases related to the XInput
+ extension and the XFree86-specific DGA extension. For our purposes,
+ the MI event queue handling should be suitable. It is initialized by
+ calling mieqInit():
+
+
+ mmiieeqqIInniitt(())
+ This MI function initializes the MI event queue for the core
+ devices, and is passed the public component of the input handles
+ for the two core devices.
+
+
+ If a wakeup handler is required to deliver synchronous input events,
+ it can be registered here by calling the DIX function
+ RegisterBlockAndWakeupHandlers(). (See the devReadInput() description
+ below.)
+
+
+ AA..11..22.. IInniittAAnnddSSttaarrttDDeevviicceess(())
+
+ InitAndStartDevices() is a DIX function that is called immediately
+ after InitInput() from the X server's main() function. Its purpose is
+ to initialize each input device that was registered with
+ AddInputDevice(), enable each input device that was successfully
+ initialized, and create the list of enabled input devices. Once each
+ registered device is processed in this way, the list of enabled input
+ devices is checked to make sure that both a core keyboard device and
+ core pointer device were registered and successfully enabled. If not,
+ InitAndStartDevices() returns failure, and results in the the X server
+ exiting with a fatal error.
+
+
+ Each registered device is initialized by calling its callback
+ (dev->deviceProc) with the DEVICE_INIT argument:
+
+
+ ((**ddeevv-->>ddeevviicceePPrroocc))((ddeevv,, DDEEVVIICCEE__IINNIITT))
+ This function initializes the device structs with core
+ information relevant to the device.
+
+
+ For pointer devices, this means specifying the number of
+ buttons, default button mapping, the function used to get motion
+ events (usually miPointerGetMotionEvents()), the function used
+ to change/control the core pointer motion parameters
+ (acceleration and threshold), and the motion buffer size.
+
+
+ For keyboard devices, this means specifying the keycode range,
+ default keycode to keysym mapping, default modifier mapping, and
+ the functions used to sound the keyboard bell and modify/control
+ the keyboard parameters (LEDs, bell pitch and duration, key
+ click, which keys are auto-repeating, etc).
+
+
+ Each initialized device is enabled by calling EnableDevice():
+
+
+ EEnnaabblleeDDeevviiccee(())
+ EnableDevice() calls the device callback with DEVICE_ON:
+
+ ((**ddeevv-->>ddeevviicceePPrroocc))((ddeevv,, DDEEVVIICCEE__OONN))
+ This typically opens and initializes the relevant physical
+ device, and when appropriate, registers the device's file
+ descriptor (or equivalent) as a valid input source.
+
+
+ EnableDevice() then adds the device handle to the X server's
+ global list of enabled devices.
+
+
+ InitAndStartDevices() then verifies that a valid core keyboard and
+ pointer has been initialized and enabled. It returns failure if
+ either are missing.
+
+
+ AA..11..33.. ddeevvRReeaaddIInnppuutt(())
+
+ Each device will have some function that gets called to read its
+ physical input. These may be called in a number of different ways.
+ In the case of synchronous I/O, they will be called from a DDX wakeup-
+ handler that gets called after the server detects that new input is
+ available. In the case of asynchronous I/O, they will be called from
+ a (SIGIO) signal handler triggered when new input is available. This
+ function should do at least two things: make sure that input events
+ get enqueued, and make sure that the cursor gets moved for motion
+ events (except if these are handled later by the driver's own event
+ queue processing function, which cannot be done when using the MI
+ event queue handling).
+
+
+ Events are queued by calling mieqEnqueue():
+
+
+ mmiieeqqEEnnqquueeuuee(())
+ This MI function is used to add input events to the event queue.
+ It is simply passed the event to be queued.
+
+
+ The cursor position should be updated when motion events are enqueued,
+ by calling either miPointerAbsoluteCursor() or miPointerDeltaCursor():
+
+
+ mmiiPPooiinntteerrAAbbssoolluutteeCCuurrssoorr(())
+ This MI function is used to move the cursor to the absolute
+ coordinates provided.
+
+ mmiiPPooiinntteerrDDeellttaaCCuurrssoorr(())
+ This MI function is used to move the cursor relative to its
+ current position.
+
+
+ AA..11..44.. PPrroocceessssIInnppuuttEEvveennttss(())
+
+ ProcessInputEvents() is a DDX function that is called from the X
+ server's main dispatch loop when new events are available in the input
+ event queue. It typically processes the enqueued events, and updates
+ the cursor/pointer position. It may also do other DDX-specific event
+ processing.
+
+
+ Enqueued events are processed by mieqProcessInputEvents() and passed
+ to the DIX layer for transmission to clients:
+
+
+ mmiieeqqPPrroocceessssIInnppuuttEEvveennttss(())
+ This function processes each event in the event queue, and
+ passes it to the device's input processing function. The DIX
+ layer provides default functions to do this processing, and they
+ handle the task of getting the events passed back to the
+ relevant clients.
+
+ mmiiPPooiinntteerrUUppddaattee(())
+ This function resynchronized the cursor position with the new
+ pointer position. It also takes care of moving the cursor
+ between screens when needed in multi-head configurations.
+
+
+
+ AA..11..55.. DDiissaabblleeDDeevviiccee(())
+
+ DisableDevice is a DIX function that removes an input device from the
+ list of enabled devices. The result of this is that the device no
+ longer generates input events. The device's data structures are kept
+ in place, and disabling a device like this can be reversed by calling
+ EnableDevice(). DisableDevice() may be called from the DDX when it is
+ desirable to do so (e.g., the XFree86 server does this when VT
+ switching). Except for special cases, this is not normally called for
+ core input devices.
+
+
+ DisableDevice() calls the device's callback function with DEVICE_OFF:
+
+
+ ((**ddeevv-->>ddeevviicceePPrroocc))((ddeevv,, DDEEVVIICCEE__OOFFFF))
+ This typically closes the relevant physical device, and when
+ appropriate, unregisters the device's file descriptor (or
+ equivalent) as a valid input source.
+
+
+ DisableDevice() then removes the device handle from the X server's
+ global list of enabled devices.
+
+
+
+ AA..11..66.. CClloosseeDDeevviiccee(())
+
+ CloseDevice is a DIX function that removes an input device from the
+ list of available devices. It disables input from the device and
+ frees all data structures associated with the device. This function
+ is usually called from CloseDownDevices(), which is called from main()
+ at the end of each server generation to close all input devices.
+
+
+ CloseDevice() calls the device's callback function with DEVICE_CLOSE:
+
+
+ ((**ddeevv-->>ddeevviicceePPrroocc))((ddeevv,, DDEEVVIICCEE__CCLLOOSSEE))
+ This typically closes the relevant physical device, and when
+ appropriate, unregisters the device's file descriptor (or
+ equivalent) as a valid input source. If any device specific
+ data structures were allocated when the device was initialized,
+ they are freed here.
+
+ CloseDevice() then frees the data structures that were allocated for
+ the device when it was registered/initialized.
+
+
+
+ AA..11..77.. LLeeggaallMMooddiiffiieerr(())
+
+ LegalModifier() is a required DDX function that can be used to
+ restrict which keys may be modifier keys. This seems to be present
+ for historical reasons, so this function should simply return TRUE
+ unconditionally.
+
+
+
+ AA..22.. OOuuttppuutt hhaannddlliinngg
+
+ The following sections describe the main functions required to
+ initialize, use and close the output device(s) for each screen in the
+ X server.
+
+
+ AA..22..11.. IInniittOOuuttppuutt(())
+
+ This DDX function is called near the start of each server generation
+ from the X server's main() function. InitOutput()'s main purpose is
+ to initialize each screen and fill in the global screenInfo structure
+ for each screen. It is passed three arguments: a pointer to the
+ screenInfo struct, which it is to initialize, and argc and argv from
+ main(), which can be used to determine additional configuration
+ information.
+
+
+ The primary tasks for this function are outlined below:
+
+
+ 1. PPaarrssee ccoonnffiigguurraattiioonn iinnffoo:: The first task of InitOutput() is to
+ parses any configuration information from the configuration file.
+ In addition to the XF86Config file, other configuration information
+ can be taken from the command line. The command line options can
+ be gathered either in InitOutput() or earlier in the
+ ddxProcessArgument() function, which is called by
+ ProcessCommandLine(). The configuration information determines the
+ characteristics of the screen(s). For example, in the XFree86 X
+ server, the XF86Config file specifies the monitor information, the
+ screen resolution, the graphics devices and slots in which they are
+ located, and, for Xinerama, the screens' layout.
+
+ 2. IInniittiiaalliizzee ssccrreeeenn iinnffoo:: The next task is to initialize the screen-
+ dependent internal data structures. For example, part of what the
+ XFree86 X server does is to allocate its screen and pixmap private
+ indices, probe for graphics devices, compare the probed devices to
+ the ones listed in the XF86Config file, and add the ones that match
+ to the internal xf86Screens[] structure.
+
+ 3. SSeett ppiixxmmaapp ffoorrmmaattss:: The next task is to initialize the screenInfo's
+ image byte order, bitmap bit order and bitmap scanline unit/pad.
+ The screenInfo's pixmap format's depth, bits per pixel and scanline
+ padding is also initialized at this stage.
+
+ 4. UUnniiffyy ssccrreeeenn iinnffoo:: An optional task that might be done at this
+ stage is to compare all of the information from the various screens
+ and determines if they are compatible (i.e., if the set of screens
+ can be unified into a single desktop). This task has potential to
+ be useful to the DMX front-end server, if Xinerama's
+ PanoramiXConsolidate() function is not sufficient.
+
+ Once these tasks are complete, the valid screens are known and each of
+ these screens can be initialized by calling AddScreen().
+
+
+ AA..22..22.. AAddddSSccrreeeenn(())
+
+ This DIX function is called from InitOutput(), in the DDX layer, to
+ add each new screen to the screenInfo structure. The DDX screen
+ initialization function and command line arguments (i.e., argc and
+ argv) are passed to it as arguments.
+
+
+ This function first allocates a new Screen structure and any privates
+ that are required. It then initializes some of the fields in the
+ Screen struct and sets up the pixmap padding information. Finally, it
+ calls the DDX screen initialization function ScreenInit(), which is
+ described below. It returns the number of the screen that were just
+ added, or -1 if there is insufficient memory to add the screen or if
+ the DDX screen initialization fails.
+
+
+ AA..22..33.. SSccrreeeennIInniitt(())
+
+ This DDX function initializes the rest of the Screen structure with
+ either generic or screen-specific functions (as necessary). It also
+ fills in various screen attributes (e.g., width and height in
+ millimeters, black and white pixel values).
+
+
+ The screen init function usually calls several functions to perform
+ certain screen initialization functions. They are described below:
+
+
+ {{mmii,,**ffbb}}SSccrreeeennIInniitt(())
+ The DDX layer's ScreenInit() function usually calls another
+ layer's ScreenInit() function (e.g., miScreenInit() or
+ fbScreenInit()) to initialize the fallbacks that the DDX driver
+ does not specifically handle.
+
+
+ After calling another layer's ScreenInit() function, any screen-
+ specific functions either wrap or replace the other layer's
+ function pointers. If a function is to be wrapped, each of the
+ old function pointers from the other layer are stored in a
+ screen private area. Common functions to wrap are CloseScreen()
+ and SaveScreen().
+
+
+ mmiiIInniittiiaalliizzeeBBaacckkiinnggSSttoorree(())
+ This MI function initializes the screen's backing storage
+ functions, which are used to save areas of windows that are
+ currently covered by other windows.
+
+
+ mmiiDDCCIInniittiiaalliizzee(())
+ This MI function initializes the MI cursor display structures
+ and function pointers. If a hardware cursor is used, the DDX
+ layer's ScreenInit() function will wrap additional screen and
+ the MI cursor display function pointers.
+
+
+ Another common task for ScreenInit() function is to initialize the
+ output device state. For example, in the XFree86 X server, the
+ ScreenInit() function saves the original state of the video card and
+ then initializes the video mode of the graphics device.
+
+ AA..22..44.. CClloosseeSSccrreeeenn(())
+
+ This function restores any wrapped screen functions (and in particular
+ the wrapped CloseScreen() function) and restores the state of the
+ output device to its original state. It should also free any private
+ data it created during the screen initialization.
+
+
+ AA..22..55.. GGCC ooppeerraattiioonnss
+
+ When the X server is requested to render drawing primitives, it does
+ so by calling drawing functions through the graphics context's
+ operation function pointer table (i.e., the GCOps functions). These
+ functions render the basic graphics operations such as drawing
+ rectangles, lines, text or copying pixmaps. Default routines are
+ provided either by the MI layer, which draws indirectly through a
+ simple span interface, or by the framebuffer layers (e.g., CFB, MFB,
+ FB), which draw directly to a linearly mapped frame buffer.
+
+
+ To take advantage of special hardware on the graphics device, specific
+ GCOps functions can be replaced by device specific code. However,
+ many times the graphics devices can handle only a subset of the
+ possible states of the GC, so during graphics context validation,
+ appropriate routines are selected based on the state and capabilities
+ of the hardware. For example, some graphics hardware can accelerate
+ single pixel width lines with certain dash patterns. Thus, for dash
+ patterns that are not supported by hardware or for width 2 or greater
+ lines, the default routine is chosen during GC validation.
+
+
+ Note that some pointers to functions that draw to the screen are
+ stored in the Screen structure. They include GetImage(), GetSpans(),
+ PaintWindowBackground(), PaintWindowBorder(), CopyWindow() and
+ RestoreAreas().
+
+
+ AA..22..66.. XXnneesstt
+
+ The Xnest X server is a special proxy X server that relays the X
+ protocol requests that it receives to a ``real'' X server that then
+ processes the requests and displays the results, if applicable. To
+ the X applications, Xnest appears as if it is a regular X server.
+ However, Xnest is both server to the X application and client of the
+ real X server, which will actually handle the requests.
+
+
+ The Xnest server implements all of the standard input and output
+ initialization steps outlined above.
+
+
+ IInniittOOuuttppuutt(())
+ Xnest takes its configuration information from command line
+ arguments via ddxProcessArguments(). This information includes
+ the real X server display to connect to, its default visual
+ class, the screen depth, the Xnest window's geometry, etc.
+ Xnest then connects to the real X server and gathers visual,
+ colormap, depth and pixmap information about that server's
+ display, creates a window on that server, which will be used as
+ the root window for Xnest.
+
+
+ Next, Xnest initializes its internal data structures and uses
+ the data from the real X server's pixmaps to initialize its own
+ pixmap formats. Finally, it calls AddScreen(xnestOpenScreen,
+ argc, argv) to initialize each of its screens.
+ SSccrreeeennIInniitt(())
+ Xnest's ScreenInit() function is called xnestOpenScreen(). This
+ function initializes its screen's depth and visual information,
+ and then calls miScreenInit() to set up the default screen
+ functions. It then calls miInitializeBackingStore() and
+ miDCInitialize() to initialize backing store and the software
+ cursor. Finally, it replaces many of the screen functions with
+ its own functions that repackage and send the requests to the
+ real X server to which Xnest is attached.
+
+
+ CClloosseeSSccrreeeenn(())
+ This function frees its internal data structure allocations.
+ Since it replaces instead of wrapping screen functions, there
+ are no function pointers to unwrap. This can potentially lead
+ to problems during server regeneration.
+
+
+ GGCC ooppeerraattiioonnss
+ The GC operations in Xnest are very simple since they leave all
+ of the drawing to the real X server to which Xnest is attached.
+ Each of the GCOps takes the request and sends it to the real X
+ server using standard Xlib calls. For example, the X
+ application issues a XDrawLines() call. This function turns
+ into a protocol request to Xnest, which calls the
+ xnestPolylines() function through Xnest's GCOps function pointer
+ table. The xnestPolylines() function is only a single line,
+ which calls XDrawLines() using the same arguments that were
+ passed into it. Other GCOps functions are very similar. Two
+ exceptions to the simple GCOps functions described above are the
+ image functions and the BLT operations.
+
+
+ The image functions, GetImage() and PutImage(), must use a
+ temporary image to hold the image to be put of the image that
+ was just grabbed from the screen while it is in transit to the
+ real X server or the client. When the image has been
+ transmitted, the temporary image is destroyed.
+
+
+ The BLT operations, CopyArea() and CopyPlane(), handle not only
+ the copy function, which is the same as the simple cases
+ described above, but also the graphics exposures that result
+ when the GC's graphics exposure bit is set to True. Graphics
+ exposures are handled in a helper function,
+ xnestBitBlitHelper(). This function collects the exposure
+ events from the real X server and, if any resulting in regions
+ being exposed, then those regions are passed back to the MI
+ layer so that it can generate exposure events for the X
+ application.
+
+
+ The Xnest server takes its input from the X server to which it is
+ connected. When the mouse is in the Xnest server's window, keyboard
+ and mouse events are received by the Xnest server, repackaged and sent
+ back to any client that requests those events.
+
+
+ AA..22..77.. SShhaaddooww ffrraammeebbuuffffeerr
+
+ The most common type of framebuffer is a linear array memory that maps
+ to the video memory on the graphics device. However, accessing that
+ video memory over an I/O bus (e.g., ISA or PCI) can be slow. The
+ shadow framebuffer layer allows the developer to keep the entire
+ framebuffer in main memory and copy it back to video memory at regular
+ intervals. It also has been extended to handle planar video memory
+ and rotated framebuffers.
+
+
+ There are two main entry points to the shadow framebuffer code:
+
+
+ sshhaaddoowwAAlllloocc((wwiiddtthh,, hheeiigghhtt,, bbpppp))
+ This function allocates the in memory copy of the framebuffer of
+ size width*height*bpp. It returns a pointer to that memory,
+ which will be used by the framebuffer ScreenInit() code during
+ the screen's initialization.
+
+
+ sshhaaddoowwIInniitt((ppSSccrreeeenn,, uuppddaatteePPrroocc,, wwiinnddoowwPPrroocc))
+ This function initializes the shadow framebuffer layer. It
+ wraps several screen drawing functions, and registers a block
+ handler that will update the screen. The updateProc is a
+ function that will copy the damaged regions to the screen, and
+ the windowProc is a function that is used when the entire linear
+ video memory range cannot be accessed simultaneously so that
+ only a window into that memory is available (e.g., when using
+ the VGA aperture).
+
+
+ The shadow framebuffer code keeps track of the damaged area of each
+ screen by calculating the bounding box of all drawing operations that
+ have occurred since the last screen update. Then, when the block
+ handler is next called, only the damaged portion of the screen is
+ updated.
+
+
+ Note that since the shadow framebuffer is kept in main memory, all
+ drawing operations are performed by the CPU and, thus, no accelerated
+ hardware drawing operations are possible.
+
+
+
+ AA..33.. XXiinneerraammaa
+
+ Xinerama is an X extension that allows multiple physical screens
+ controlled by a single X server to appear as a single screen.
+ Although the extension allows clients to find the physical screen
+ layout via extension requests, it is completely transparent to clients
+ at the core X11 protocol level. The original public implementation of
+ Xinerama came from Digital/Compaq. XFree86 rewrote it, filling in
+ some missing pieces and improving both X11 core protocol compliance
+ and performance. The Xinerama extension will be passing through
+ X.Org's standardization process in the near future, and the sample
+ implementation will be based on this rewritten version.
+
+
+ The current implementation of Xinerama is based primarily in the DIX
+ (device independent) and MI (machine independent) layers of the X
+ server. With few exceptions the DDX layers do not need any changes to
+ support Xinerama. X server extensions often do need modifications to
+ provide full Xinerama functionality.
+
+
+ The following is a code-level description of how Xinerama functions.
+
+
+ Note: Because the Xinerama extension was originally called the
+ PanoramiX extension, many of the Xinerama functions still have the
+ PanoramiX prefix.
+
+
+ PPaannoorraammiiXXEExxtteennssiioonnIInniitt(())
+ PanoramiXExtensionInit() is a device-independent extension
+ function that is called at the start of each server generation
+ from InitExtensions(), which is called from the X server's
+ main() function after all output devices have been initialized,
+ but before any input devices have been initialized.
+
+
+ PanoramiXNumScreens is set to the number of physical screens.
+ If only one physical screen is present, the extension is
+ disabled, and PanoramiXExtensionInit() returns without doing
+ anything else.
+
+
+ The Xinerama extension is registered by calling AddExtension().
+
+
+ A local per-screen array of data structures (panoramiXdataPtr[])
+ is allocated for each physical screen, and GC and Screen private
+ indexes are allocated, and both GC and Screen private areas are
+ allocated for each physical screen. These hold Xinerama-
+ specific per-GC and per-Screen data. Each screen's CreateGC and
+ CloseScreen functions are wrapped by XineramaCreateGC() and
+ XineramaCloseScreen() respectively. Some new resource classes
+ are created for Xinerama drawables and GCs, and resource types
+ for Xinerama windows, pixmaps and colormaps.
+
+
+ A region (XineramaScreenRegions[i]) is initialized for each
+ physical screen, and single region (PanoramiXScreenRegion) is
+ initialized to be the union of the screen regions. The
+ panoramiXdataPtr[] array is also initialized with the size and
+ origin of each screen. The relative positioning information for
+ the physical screens is taken from the array dixScreenOrigins[],
+ which the DDX layer must initialize in InitOutput(). The bounds
+ of the combined screen is also calculated (PanoramiXPixWidth and
+ PanoramiXPixHeight).
+
+
+ The DIX layer has a list of function pointers (ProcVector[])
+ that holds the entry points for the functions that process core
+ protocol requests. The requests that Xinerama must intercept
+ and break up into physical screen-specific requests are wrapped.
+ The original set is copied to SavedProcVector[]. The types of
+ requests intercepted are Window requests, GC requests, colormap
+ requests, drawing requests, and some geometry-related requests.
+ This wrapping allows the bulk of the protocol request processing
+ to be handled transparently to the DIX layer. Some operations
+ cannot be dealt with in this way and are handled with Xinerama-
+ specific code within the DIX layer.
+
+
+ PPaannoorraammiiXXCCoonnssoolliiddaattee(())
+ PanoramiXConsolidate() is a device-independent extension
+ function that is called directly from the X server's main()
+ function after extensions and input/output devices have been
+ initialized, and before the root windows are defined and
+ initialized.
+
+
+ This function finds the set of depths (PanoramiXDepths[]) and
+ visuals (PanoramiXVisuals[]) common to all of the physical
+ screens. PanoramiXNumDepths is set to the number of common
+ depths, and PanoramiXNumVisuals is set to the number of common
+ visuals. Resources are created for the single root window and
+ the default colormap. Each of these resources has per-physical
+ screen entries.
+
+
+ PPaannoorraammiiXXCCrreeaatteeCCoonnnneeccttiioonnBBlloocckk(())
+ PanoramiXConsolidate() is a device-independent extension
+ function that is called directly from the X server's main()
+ function after the per-physical screen root windows are created.
+ It is called instead of the standard DIX CreateConnectionBlock()
+ function. If this function returns FALSE, the X server exits
+ with a fatal error. This function will return FALSE if no
+ common depths were found in PanoramiXConsolidate(). With no
+ common depths, Xinerama mode is not possible.
+
+
+ The connection block holds the information that clients get when
+ they open a connection to the X server. It includes information
+ such as the supported pixmap formats, number of screens and the
+ sizes, depths, visuals, default colormap information, etc, for
+ each of the screens (much of information that xdpyinfo shows).
+ The connection block is initialized with the combined single
+ screen values that were calculated in the above two functions.
+
+
+ The Xinerama extension allows the registration of connection
+ block callback functions. The purpose of these is to allow
+ other extensions to do processing at this point. These
+ callbacks can be registered by calling
+ XineramaRegisterConnectionBlockCallback() from the other
+ extension's ExtensionInit() function. Each registered
+ connection block callback is called at the end of
+ PanoramiXCreateConnectionBlock().
+
+
+ AA..33..11.. XXiinneerraammaa--ssppeecciiffiicc cchhaannggeess ttoo tthhee DDIIXX ccooddee
+
+ There are a few types of Xinerama-specific changes within the DIX
+ code. The main ones are described here.
+
+
+ Functions that deal with colormap or GC -related operations outside of
+ the intercepted protocol requests have a test added to only do the
+ processing for screen numbers > 0. This is because they are handled
+ for the single Xinerama screen and the processing is done once for
+ screen 0.
+
+
+ The handling of motion events does some coordinate translation between
+ the physical screen's origin and screen zero's origin. Also, motion
+ events must be reported relative to the composite screen origin rather
+ than the physical screen origins.
+
+
+ There is some special handling for cursor, window and event processing
+ that cannot (either not at all or not conveniently) be done via the
+ intercepted protocol requests. A particular case is the handling of
+ pointers moving between physical screens.
+
+
+ AA..33..22.. XXiinneerraammaa--ssppeecciiffiicc cchhaannggeess ttoo tthhee MMII ccooddee
+
+ The only Xinerama-specific change to the MI code is in
+ miSendExposures() to handle the coordinate (and window ID) translation
+ for expose events.
+
+
+
+ AA..33..33.. IInntteerrcceepptteedd DDIIXX ccoorree rreeqquueessttss
+
+ Xinerama breaks up drawing requests for dispatch to each physical
+ screen. It also breaks up windows into pieces for each physical
+ screen. GCs are translated into per-screen GCs. Colormaps are
+ replicated on each physical screen. The functions handling the
+ intercepted requests take care of breaking the requests and
+ repackaging them so that they can be passed to the standard request
+ handling functions for each screen in turn. In addition, and to aid
+ the repackaging, the information from many of the intercepted requests
+ is used to keep up to date the necessary state information for the
+ single composite screen. Requests (usually those with replies) that
+ can be satisfied completely from this stored state information do not
+ call the standard request handling functions.
+
+
+
+ BB.. DDeevveellooppmmeenntt RReessuullttss
+
+ In this section the results of each phase of development are
+ discussed. This development took place between approximately June
+ 2001 and July 2003.
+
+
+ BB..11.. PPhhaassee II
+
+ The initial development phase dealt with the basic implementation
+ including the bootstrap code, which used the shadow framebuffer, and
+ the unoptimized implementation, based on an Xnest-style
+ implementation.
+
+
+ BB..11..11.. SSccooppee
+
+ The goal of Phase I is to provide fundamental functionality that can
+ act as a foundation for ongoing work:
+
+ 1. Develop the proxy X server
+
+ +o The proxy X server will operate on the X11 protocol and relay
+ requests as necessary to correctly perform the request.
+
+ +o Work will be based on the existing work for Xinerama and Xnest.
+
+ +o Input events and windowing operations are handled in the proxy
+ server and rendering requests are repackaged and sent to each of
+ the back-end servers for display.
+
+ +o The multiple screen layout (including support for overlapping
+ screens) will be user configurable via a configuration file or
+ through the configuration tool.
+
+ 2. Develop graphical configuration tool
+
+ +o There will be potentially a large number of X servers to
+ configure into a single display. The tool will allow the user
+ to specify which servers are involved in the configuration and
+ how they should be laid out.
+
+ 3. Pass the X Test Suite
+
+ +o The X Test Suite covers the basic X11 operations. All tests
+ known to succeed must correctly operate in the distributed X
+ environment.
+
+
+ For this phase, the back-end X servers are assumed to be unmodified X
+ servers that do not support any DMX-related protocol extensions;
+ future optimization pathways are considered, but are not implemented;
+ and the configuration tool is assumed to rely only on libraries in the
+ X source tree (e.g., Xt).
+
+
+ BB..11..22.. RReessuullttss
+
+ The proxy X server, Xdmx, was developed to distribute X11 protocol
+ requests to the set of back-end X servers. It opens a window on each
+ back-end server, which represents the part of the front-end's root
+ window that is visible on that screen. It mirrors window, pixmap and
+ other state in each back-end server. Drawing requests are sent to
+ either windows or pixmaps on each back-end server. This code is based
+ on Xnest and uses the existing Xinerama extension.
+
+
+ Input events can be taken from (1) devices attached to the back-end
+ server, (2) core devices attached directly to the Xdmx server, or (3)
+ from a ``console'' window on another X server. Events for these
+ devices are gathered, processed and delivered to clients attached to
+ the Xdmx server.
+
+
+ An intuitive configuration format was developed to help the user
+ easily configure the multiple back-end X servers. It was defined (see
+ grammar in Xdmx man page) and a parser was implemented that is used by
+ the Xdmx server and by a standalone xdmxconfig utility. The parsing
+ support was implemented such that it can be easily factored out of the
+ X source tree for use with other tools (e.g., vdl). Support for
+ converting legacy vdl-format configuration files to the DMX format is
+ provided by the vdltodmx utility.
+
+
+ Originally, the configuration file was going to be a subsection of
+ XFree86's XF86Config file, but that was not possible since Xdmx is a
+ completely separate X server. Thus, a separate config file format was
+ developed. In addition, a graphical configuration tool, xdmxconfig,
+ was developed to allow the user to create and arrange the screens in
+ the configuration file. The --ccoonnffiiggffiillee and --ccoonnffiigg command-line
+ options can be used to start Xdmx using a configuration file.
+
+
+ An extension that enables remote input testing is required for the X
+ Test Suite to function. During this phase, this extension (XTEST) was
+ implemented in the Xdmx server. The results from running the X Test
+ Suite are described in detail below.
+
+
+ BB..11..33.. XX TTeesstt SSuuiittee
+
+ BB..11..33..11.. IInnttrroodduuccttiioonn
+
+ The X Test Suite contains tests that verify Xlib functions operate
+ correctly. The test suite is designed to run on a single X server;
+ however, since X applications will not be able to tell the difference
+ between the DMX server and a standard X server, the X Test Suite
+ should also run on the DMX server.
+
+ The Xdmx server was tested with the X Test Suite, and the existing
+ failures are noted in this section. To put these results in
+ perspective, we first discuss expected X Test failures and how errors
+ in underlying systems can impact Xdmx test results.
+
+
+ BB..11..33..22.. EExxppeecctteedd FFaaiilluurreess ffoorr aa SSiinnggllee HHeeaadd
+
+ A correctly implemented X server with a single screen is expected to
+ fail certain X Test tests. The following well-known errors occur
+ because of rounding error in the X server code:
+
+ XDrawArc: Tests 42, 63, 66, 73
+ XDrawArcs: Tests 45, 66, 69, 76
+
+
+
+ The following failures occur because of the high-level X server
+ implementation:
+
+ XLoadQueryFont: Test 1
+ XListFontsWithInfo: Tests 3, 4
+ XQueryFont: Tests 1, 2
+
+
+
+ The following test fails when running the X server as root under Linux
+ because of the way directory modes are interpreted:
+
+ XWriteBitmapFile: Test 3
+
+
+
+ Depending on the video card used for the back-end, other failures may
+ also occur because of bugs in the low-level driver implementation.
+ Over time, failures of this kind are usually fixed by XFree86, but
+ will show up in Xdmx testing until then.
+
+
+ BB..11..33..33.. EExxppeecctteedd FFaaiilluurreess ffoorr XXiinneerraammaa
+
+ Xinerama fails several X Test Suite tests because of design decisions
+ made for the current implementation of Xinerama. Over time, many of
+ these errors will be corrected by XFree86 and the group working on a
+ new Xinerama implementation. Therefore, Xdmx will also share X Suite
+ Test failures with Xinerama.
+
+ We may be able to fix or work-around some of these failures at the
+ Xdmx level, but this will require additional exploration that was not
+ part of Phase I.
+
+ Xinerama is constantly improving, and the list of Xinerama-related
+ failures depends on XFree86 version and the underlying graphics
+ hardware. We tested with a variety of hardware, including nVidia, S3,
+ ATI Radeon, and Matrox G400 (in dual-head mode). The list below
+ includes only those failures that appear to be from the Xinerama
+ layer, and does not include failures listed in the previous section,
+ or failures that appear to be from the low-level graphics driver
+ itself:
+
+ These failures were noted with multiple Xinerama configurations:
+
+ XCopyPlane: Tests 13, 22, 31 (well-known Xinerama implementation issue)
+ XSetFontPath: Test 4
+ XGetDefault: Test 5
+ XMatchVisualInfo: Test 1
+
+
+
+ These failures were noted only when using one dual-head video card
+ with a 4.2.99.x XFree86 server:
+
+ XListPixmapFormats: Test 1
+ XDrawRectangles: Test 45
+
+
+
+ These failures were noted only when using two video cards from
+ different vendors with a 4.1.99.x XFree86 server:
+
+ XChangeWindowAttributes: Test 32
+ XCreateWindow: Test 30
+ XDrawLine: Test 22
+ XFillArc: Test 22
+ XChangeKeyboardControl: Tests 9, 10
+ XRebindKeysym: Test 1
+
+
+
+ BB..11..33..44.. AAddddiittiioonnaall FFaaiilluurreess ffrroomm XXddmmxx
+
+ When running Xdmx, no unexpected failures were noted. Since the Xdmx
+ server is based on Xinerama, we expect to have most of the Xinerama
+ failures present in the Xdmx server. Similarly, since the Xdmx server
+ must rely on the low-level device drivers on each back-end server, we
+ also expect that Xdmx will exhibit most of the back-end failures.
+ Here is a summary:
+
+ XListPixmapFormats: Test 1 (configuration dependent)
+ XChangeWindowAttributes: Test 32
+ XCreateWindow: Test 30
+ XCopyPlane: Test 13, 22, 31
+ XSetFontPath: Test 4
+ XGetDefault: Test 5 (configuration dependent)
+ XMatchVisualInfo: Test 1
+ XRebindKeysym: Test 1 (configuration dependent)
+
+
+
+ Note that this list is shorter than the combined list for Xinerama
+ because Xdmx uses different code paths to perform some Xinerama
+ operations. Further, some Xinerama failures have been fixed in the
+ XFree86 4.2.99.x CVS repository.
+
+
+ BB..11..33..55.. SSuummmmaarryy aanndd FFuuttuurree WWoorrkk
+
+ Running the X Test Suite on Xdmx does not produce any failures that
+ cannot be accounted for by the underlying Xinerama subsystem used by
+ the front-end or by the low-level device-driver code running on the
+ back-end X servers. The Xdmx server therefore is as ``correct'' as
+ possible with respect to the standard set of X Test Suite tests.
+
+ During the following phases, we will continue to verify Xdmx
+ correctness using the X Test Suite. We may also use other tests
+ suites or write additional tests that run under the X Test Suite that
+ specifically verify the expected behavior of DMX.
+
+
+
+ BB..11..44.. FFoonnttss
+
+ In Phase I, fonts are handled directly by both the front-end and the
+ back-end servers, which is required since we must treat each back-end
+ server during this phase as a ``black box''. What this requires is
+ that tthhee ffrroonntt-- aanndd bbaacckk--eenndd sseerrvveerrss mmuusstt sshhaarree tthhee eexxaacctt ssaammee ffoonntt
+ ppaatthh. There are two ways to help make sure that all servers share the
+ same font path:
+
+
+ 1. First, each server can be configured to use the same font server.
+ The font server, xfs, can be configured to serve fonts to multiple
+ X servers via TCP.
+
+ 2. Second, each server can be configured to use the same font path and
+ either those font paths can be copied to each back-end machine or
+ they can be mounted (e.g., via NFS) on each back-end machine.
+
+
+ One additional concern is that a client program can set its own font
+ path, and if it does so, then that font path must be available on each
+ back-end machine.
+
+
+ The -fontpath command line option was added to allow users to
+ initialize the font path of the front end server. This font path is
+ propagated to each back-end server when the default font is loaded.
+ If there are any problems, an error message is printed, which will
+ describe the problem and list the current font path. For more
+ information about setting the font path, see the -fontpath option
+ description in the man page.
+
+
+ BB..11..55.. PPeerrffoorrmmaannccee
+
+ Phase I of development was not intended to optimize performance. Its
+ focus was on completely and correctly handling the base X11 protocol
+ in the Xdmx server. However, several insights were gained during
+ Phase I, which are listed here for reference during the next phase of
+ development.
+
+
+ 1. Calls to XSync() can slow down rendering since it requires a
+ complete round trip to and from a back-end server. This is
+ especially problematic when communicating over long haul networks.
+
+ 2. Sending drawing requests to only the screens that they overlap
+ should improve performance.
+
+
+ BB..11..66.. PPiixxmmaappss
+
+ Pixmaps were originally expected to be handled entirely in the front-
+ end X server; however, it was found that this overly complicated the
+ rendering code and would have required sending potentially large
+ images to each back server that required them when copying from pixmap
+ to screen. Thus, pixmap state is mirrored in the back-end server just
+ as it is with regular window state. With this implementation, the
+ same rendering code that draws to windows can be used to draw to
+ pixmaps on the back-end server, and no large image transfers are
+ required to copy from pixmap to window.
+
+
+
+ BB..22.. PPhhaassee IIII
+
+ The second phase of development concentrates on performance
+ optimizations. These optimizations are documented here, with x11perf
+ data to show how the optimizations improve performance.
+
+
+ All benchmarks were performed by running Xdmx on a dual processor
+ 1.4GHz AMD Athlon machine with 1GB of RAM connecting over 100baseT to
+ two single-processor 1GHz Pentium III machines with 256MB of RAM and
+ ATI Rage 128 (RF) video cards. The front end was running Linux
+ 2.4.20-pre1-ac1 and the back ends were running Linux 2.4.7-10 and
+ version 4.2.99.1 of XFree86 pulled from the XFree86 CVS repository on
+ August 7, 2002. All systems were running Red Hat Linux 7.2.
+
+
+ BB..22..11.. MMoovviinngg ffrroomm XXFFrreeee8866 44..11..9999..11 ttoo 44..22..00..00
+
+ For phase II, the working source tree was moved to the branch tagged
+ with dmx-1-0-branch and was updated from version 4.1.99.1 (20 August
+ 2001) of the XFree86 sources to version 4.2.0.0 (18 January 2002).
+ After this update, the following tests were noted to be more than 10%
+ faster:
+
+ 1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple)
+ 1.16 Fill 1x1 tiled trapezoid (161x145 tile)
+ 1.13 Fill 10x10 tiled trapezoid (161x145 tile)
+ 1.17 Fill 100x100 tiled trapezoid (161x145 tile)
+ 1.16 Fill 1x1 tiled trapezoid (216x208 tile)
+ 1.20 Fill 10x10 tiled trapezoid (216x208 tile)
+ 1.15 Fill 100x100 tiled trapezoid (216x208 tile)
+ 1.37 Circulate Unmapped window (200 kids)
+
+
+
+ And the following tests were noted to be more than 10% slower:
+
+ 0.88 Unmap window via parent (25 kids)
+ 0.75 Circulate Unmapped window (4 kids)
+ 0.79 Circulate Unmapped window (16 kids)
+ 0.80 Circulate Unmapped window (25 kids)
+ 0.82 Circulate Unmapped window (50 kids)
+ 0.85 Circulate Unmapped window (75 kids)
+
+
+
+ These changes were not caused by any changes in the DMX system, and
+ may point to changes in the XFree86 tree or to tests that have more
+ "jitter" than most other x11perf tests.
+
+
+ BB..22..22.. GGlloobbaall cchhaannggeess
+
+ During the development of the Phase II DMX server, several global
+ changes were made. These changes were also compared with the Phase I
+ server. The following tests were noted to be more than 10% faster:
+
+
+
+ 1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple)
+ 1.15 Fill 1x1 tiled trapezoid (161x145 tile)
+ 1.13 Fill 10x10 tiled trapezoid (161x145 tile)
+ 1.17 Fill 100x100 tiled trapezoid (161x145 tile)
+ 1.16 Fill 1x1 tiled trapezoid (216x208 tile)
+ 1.19 Fill 10x10 tiled trapezoid (216x208 tile)
+ 1.15 Fill 100x100 tiled trapezoid (216x208 tile)
+ 1.15 Circulate Unmapped window (4 kids)
+
+
+
+ The following tests were noted to be more than 10% slower:
+
+ 0.69 Scroll 10x10 pixels
+ 0.68 Scroll 100x100 pixels
+ 0.68 Copy 10x10 from window to window
+ 0.68 Copy 100x100 from window to window
+ 0.76 Circulate Unmapped window (75 kids)
+ 0.83 Circulate Unmapped window (100 kids)
+
+
+
+ For the remainder of this analysis, the baseline of comparison will be
+ the Phase II deliverable with all optimizations disabled (unless
+ otherwise noted). This will highlight how the optimizations in
+ isolation impact performance.
+
+
+ BB..22..33.. XXSSyynncc(()) BBaattcchhiinngg
+
+ During the Phase I implementation, XSync() was called after every
+ protocol request made by the DMX server. This provided the DMX server
+ with an interactive feel, but defeated X11's protocol buffering system
+ and introduced round-trip wire latency into every operation. During
+ Phase II, DMX was changed so that protocol requests are no longer
+ followed by calls to XSync(). Instead, the need for an XSync() is
+ noted, and XSync() calls are only made every 100mS or when the DMX
+ server specifically needs to make a call to guarantee interactivity.
+ With this new system, X11 buffers protocol as much as possible during
+ a 100mS interval, and many unnecessary XSync() calls are avoided.
+
+
+ Out of more than 300 x11perf tests, 8 tests became more than 100 times
+ faster, with 68 more than 50X faster, 114 more than 10X faster, and
+ 181 more than 2X faster. See table below for summary.
+
+
+ The following tests were noted to be more than 10% slower with XSync()
+ batching on:
+
+ 0.88 500x500 tiled rectangle (161x145 tile)
+ 0.89 Copy 500x500 from window to window
+
+
+
+ BB..22..44.. OOffffssccrreeeenn OOppttiimmiizzaattiioonn
+
+ Windows span one or more of the back-end servers' screens; however,
+ during Phase I development, windows were created on every back-end
+ server and every rendering request was sent to every window regardless
+ of whether or not that window was visible. With the offscreen
+ optimization, the DMX server tracks when a window is completely off of
+ a back-end server's screen and, in that case, it does not send
+ rendering requests to those back-end windows. This optimization saves
+ bandwidth between the front and back-end servers, and it reduces the
+ number of XSync() calls. The performance tests were run on a DMX
+ system with only two back-end servers. Greater performance gains will
+ be had as the number of back-end servers increases.
+
+
+ Out of more than 300 x11perf tests, 3 tests were at least twice as
+ fast, and 146 tests were at least 10% faster. Two tests were more
+ than 10% slower with the offscreen optimization:
+
+ 0.88 Hide/expose window via popup (4 kids)
+ 0.89 Resize unmapped window (75 kids)
+
+
+
+ BB..22..55.. LLaazzyy WWiinnddooww CCrreeaattiioonn OOppttiimmiizzaattiioonn
+
+ As mentioned above, during Phase I, windows were created on every
+ back-end server even if they were not visible on that back-end. With
+ the lazy window creation optimization, the DMX server does not create
+ windows on a back-end server until they are either visible or they
+ become the parents of a visible window. This optimization builds on
+ the offscreen optimization (described above) and requires it to be
+ enabled.
+
+
+ The lazy window creation optimization works by creating the window
+ data structures in the front-end server when a client creates a
+ window, but delays creation of the window on the back-end server(s).
+ A private window structure in the DMX server saves the relevant window
+ data and tracks changes to the window's attributes and stacking order
+ for later use. The only times a window is created on a back-end
+ server are (1) when it is mapped and is at least partially overlapping
+ the back-end server's screen (tracked by the offscreen optimization),
+ or (2) when the window becomes the parent of a previously visible
+ window. The first case occurs when a window is mapped or when a
+ visible window is copied, moved or resized and now overlaps the back-
+ end server's screen. The second case occurs when starting a window
+ manager after having created windows to which the window manager needs
+ to add decorations.
+
+
+ When either case occurs, a window on the back-end server is created
+ using the data saved in the DMX server's window private data
+ structure. The stacking order is then adjusted to correctly place the
+ window on the back-end and lastly the window is mapped. From this
+ time forward, the window is handled exactly as if the window had been
+ created at the time of the client's request.
+
+
+ Note that when a window is no longer visible on a back-end server's
+ screen (e.g., it is moved offscreen), the window is not destroyed;
+ rather, it is kept and reused later if the window once again becomes
+ visible on the back-end server's screen. Originally with this
+ optimization, destroying windows was implemented but was later
+ rejected because it increased bandwidth when windows were opaquely
+ moved or resized, which is common in many window managers.
+
+
+
+ The performance tests were run on a DMX system with only two back-end
+ servers. Greater performance gains will be had as the number of back-
+ end servers increases.
+
+
+ This optimization improved the following x11perf tests by more than
+ 10%:
+
+ 1.10 500x500 rectangle outline
+ 1.12 Fill 100x100 stippled trapezoid (161x145 stipple)
+ 1.20 Circulate Unmapped window (50 kids)
+ 1.19 Circulate Unmapped window (75 kids)
+
+
+
+ BB..22..66.. SSuubbddiivviiddiinngg RReennddeerriinngg PPrriimmiittiivveess
+
+ X11 imaging requests transfer significant data between the client and
+ the X server. During Phase I, the DMX server would then transfer the
+ image data to each back-end server. Even with the offscreen
+ optimization (above), these requests still required transferring
+ significant data to each back-end server that contained a visible
+ portion of the window. For example, if the client uses XPutImage() to
+ copy an image to a window that overlaps the entire DMX screen, then
+ the entire image is copied by the DMX server to every back-end server.
+
+
+ To reduce the amount of data transferred between the DMX server and
+ the back-end servers when XPutImage() is called, the image data is
+ subdivided and only the data that will be visible on a back-end
+ server's screen is sent to that back-end server. Xinerama already
+ implements a subdivision algorithm for XGetImage() and no further
+ optimization was needed.
+
+
+ Other rendering primitives were analyzed, but the time required to
+ subdivide these primitives was a significant proportion of the time
+ required to send the entire rendering request to the back-end server,
+ so this optimization was rejected for the other rendering primitives.
+
+
+ Again, the performance tests were run on a DMX system with only two
+ back-end servers. Greater performance gains will be had as the number
+ of back-end servers increases.
+
+
+ This optimization improved the following x11perf tests by more than
+ 10%:
+
+ 1.12 Fill 100x100 stippled trapezoid (161x145 stipple)
+ 1.26 PutImage 10x10 square
+ 1.83 PutImage 100x100 square
+ 1.91 PutImage 500x500 square
+ 1.40 PutImage XY 10x10 square
+ 1.48 PutImage XY 100x100 square
+ 1.50 PutImage XY 500x500 square
+ 1.45 Circulate Unmapped window (75 kids)
+ 1.74 Circulate Unmapped window (100 kids)
+
+
+
+ The following test was noted to be more than 10% slower with this
+ optimization:
+
+ 0.88 10-pixel fill chord partial circle
+
+
+
+ BB..22..77.. SSuummmmaarryy ooff xx1111ppeerrff DDaattaa
+
+ With all of the optimizations on, 53 x11perf tests are more than 100X
+ faster than the unoptimized Phase II deliverable, with 69 more than
+ 50X faster, 73 more than 10X faster, and 199 more than twice as fast.
+ No tests were more than 10% slower than the unoptimized Phase II
+ deliverable. (Compared with the Phase I deliverable, only Circulate
+ Unmapped window (100 kids) was more than 10% slower than the Phase II
+ deliverable. As noted above, this test seems to have wider
+ variability than other x11perf tests.)
+
+
+ The following table summarizes relative x11perf test changes for all
+ optimizations individually and collectively. Note that some of the
+ optimizations have a synergistic effect when used together.
+
+
+
+ 1: XSync() batching only
+ 2: Off screen optimizations only
+ 3: Window optimizations only
+ 4: Subdivprims only
+ 5: All optimizations
+
+ 1 2 3 4 5 Operation
+ ------ ---- ---- ---- ------ ---------
+ 2.14 1.85 1.00 1.00 4.13 Dot
+ 1.67 1.80 1.00 1.00 3.31 1x1 rectangle
+ 2.38 1.43 1.00 1.00 2.44 10x10 rectangle
+ 1.00 1.00 0.92 0.98 1.00 100x100 rectangle
+ 1.00 1.00 1.00 1.00 1.00 500x500 rectangle
+ 1.83 1.85 1.05 1.06 3.54 1x1 stippled rectangle (8x8 stipple)
+ 2.43 1.43 1.00 1.00 2.41 10x10 stippled rectangle (8x8 stipple)
+ 0.98 1.00 1.00 1.00 1.00 100x100 stippled rectangle (8x8 stipple)
+ 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (8x8 stipple)
+ 1.75 1.75 1.00 1.00 3.40 1x1 opaque stippled rectangle (8x8 stipple)
+ 2.38 1.42 1.00 1.00 2.34 10x10 opaque stippled rectangle (8x8 stipple)
+ 1.00 1.00 0.97 0.97 1.00 100x100 opaque stippled rectangle (8x8 stipple)
+ 1.00 1.00 1.00 1.00 0.99 500x500 opaque stippled rectangle (8x8 stipple)
+ 1.82 1.82 1.04 1.04 3.56 1x1 tiled rectangle (4x4 tile)
+ 2.33 1.42 1.00 1.00 2.37 10x10 tiled rectangle (4x4 tile)
+ 1.00 0.92 1.00 1.00 1.00 100x100 tiled rectangle (4x4 tile)
+ 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (4x4 tile)
+ 1.94 1.62 1.00 1.00 3.66 1x1 stippled rectangle (17x15 stipple)
+ 1.74 1.28 1.00 1.00 1.73 10x10 stippled rectangle (17x15 stipple)
+ 1.00 1.00 1.00 0.89 0.98 100x100 stippled rectangle (17x15 stipple)
+ 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (17x15 stipple)
+ 1.94 1.62 1.00 1.00 3.67 1x1 opaque stippled rectangle (17x15 stipple)
+ 1.69 1.26 1.00 1.00 1.66 10x10 opaque stippled rectangle (17x15 stipple)
+ 1.00 0.95 1.00 1.00 1.00 100x100 opaque stippled rectangle (17x15 stipple)
+ 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (17x15 stipple)
+ 1.93 1.61 0.99 0.99 3.69 1x1 tiled rectangle (17x15 tile)
+ 1.73 1.27 1.00 1.00 1.72 10x10 tiled rectangle (17x15 tile)
+ 1.00 1.00 1.00 1.00 0.98 100x100 tiled rectangle (17x15 tile)
+ 1.00 1.00 0.97 0.97 1.00 500x500 tiled rectangle (17x15 tile)
+ 1.95 1.63 1.00 1.00 3.83 1x1 stippled rectangle (161x145 stipple)
+ 1.80 1.30 1.00 1.00 1.83 10x10 stippled rectangle (161x145 stipple)
+ 0.97 1.00 1.00 1.00 1.01 100x100 stippled rectangle (161x145 stipple)
+ 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (161x145 stipple)
+ 1.95 1.63 1.00 1.00 3.56 1x1 opaque stippled rectangle (161x145 stipple)
+ 1.65 1.25 1.00 1.00 1.68 10x10 opaque stippled rectangle (161x145 stipple)
+ 1.00 1.00 1.00 1.00 1.01 100x100 opaque stippled rectangle (161x145...
+ 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (161x145...
+ 1.95 1.63 0.98 0.99 3.80 1x1 tiled rectangle (161x145 tile)
+ 1.67 1.26 1.00 1.00 1.67 10x10 tiled rectangle (161x145 tile)
+ 1.13 1.14 1.14 1.14 1.14 100x100 tiled rectangle (161x145 tile)
+ 0.88 1.00 1.00 1.00 0.99 500x500 tiled rectangle (161x145 tile)
+ 1.93 1.63 1.00 1.00 3.53 1x1 tiled rectangle (216x208 tile)
+ 1.69 1.26 1.00 1.00 1.66 10x10 tiled rectangle (216x208 tile)
+ 1.00 1.00 1.00 1.00 1.00 100x100 tiled rectangle (216x208 tile)
+ 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (216x208 tile)
+ 1.82 1.70 1.00 1.00 3.38 1-pixel line segment
+ 2.07 1.56 0.90 1.00 3.31 10-pixel line segment
+ 1.29 1.10 1.00 1.00 1.27 100-pixel line segment
+ 1.05 1.06 1.03 1.03 1.09 500-pixel line segment
+ 1.30 1.13 1.00 1.00 1.29 100-pixel line segment (1 kid)
+ 1.32 1.15 1.00 1.00 1.32 100-pixel line segment (2 kids)
+ 1.33 1.16 1.00 1.00 1.33 100-pixel line segment (3 kids)
+ 1.92 1.64 1.00 1.00 3.73 10-pixel dashed segment
+ 1.34 1.16 1.00 1.00 1.34 100-pixel dashed segment
+ 1.24 1.11 0.99 0.97 1.23 100-pixel double-dashed segment
+ 1.72 1.77 1.00 1.00 3.25 10-pixel horizontal line segment
+ 1.83 1.66 1.01 1.00 3.54 100-pixel horizontal line segment
+ 1.86 1.30 1.00 1.00 1.84 500-pixel horizontal line segment
+ 2.11 1.52 1.00 0.99 3.02 10-pixel vertical line segment
+ 1.21 1.10 1.00 1.00 1.20 100-pixel vertical line segment
+ 1.03 1.03 1.00 1.00 1.02 500-pixel vertical line segment
+ 4.42 1.68 1.00 1.01 4.64 10x1 wide horizontal line segment
+ 1.83 1.31 1.00 1.00 1.83 100x10 wide horizontal line segment
+ 1.07 1.00 0.96 1.00 1.07 500x50 wide horizontal line segment
+ 4.10 1.67 1.00 1.00 4.62 10x1 wide vertical line segment
+ 1.50 1.24 1.06 1.06 1.48 100x10 wide vertical line segment
+ 1.06 1.03 1.00 1.00 1.05 500x50 wide vertical line segment
+ 2.54 1.61 1.00 1.00 3.61 1-pixel line
+ 2.71 1.48 1.00 1.00 2.67 10-pixel line
+ 1.19 1.09 1.00 1.00 1.19 100-pixel line
+ 1.04 1.02 1.00 1.00 1.03 500-pixel line
+ 2.68 1.51 0.98 1.00 3.17 10-pixel dashed line
+ 1.23 1.11 0.99 0.99 1.23 100-pixel dashed line
+ 1.15 1.08 1.00 1.00 1.15 100-pixel double-dashed line
+ 2.27 1.39 1.00 1.00 2.23 10x1 wide line
+ 1.20 1.09 1.00 1.00 1.20 100x10 wide line
+ 1.04 1.02 1.00 1.00 1.04 500x50 wide line
+ 1.52 1.45 1.00 1.00 1.52 100x10 wide dashed line
+ 1.54 1.47 1.00 1.00 1.54 100x10 wide double-dashed line
+ 1.97 1.30 0.96 0.95 1.95 10x10 rectangle outline
+ 1.44 1.27 1.00 1.00 1.43 100x100 rectangle outline
+ 3.22 2.16 1.10 1.09 3.61 500x500 rectangle outline
+ 1.95 1.34 1.00 1.00 1.90 10x10 wide rectangle outline
+ 1.14 1.14 1.00 1.00 1.13 100x100 wide rectangle outline
+ 1.00 1.00 1.00 1.00 1.00 500x500 wide rectangle outline
+ 1.57 1.72 1.00 1.00 3.03 1-pixel circle
+ 1.96 1.35 1.00 1.00 1.92 10-pixel circle
+ 1.21 1.07 0.86 0.97 1.20 100-pixel circle
+ 1.08 1.04 1.00 1.00 1.08 500-pixel circle
+ 1.39 1.19 1.03 1.03 1.38 100-pixel dashed circle
+ 1.21 1.11 1.00 1.00 1.23 100-pixel double-dashed circle
+ 1.59 1.28 1.00 1.00 1.58 10-pixel wide circle
+ 1.22 1.12 0.99 1.00 1.22 100-pixel wide circle
+ 1.06 1.04 1.00 1.00 1.05 500-pixel wide circle
+ 1.87 1.84 1.00 1.00 1.85 100-pixel wide dashed circle
+ 1.90 1.93 1.01 1.01 1.90 100-pixel wide double-dashed circle
+ 2.13 1.43 1.00 1.00 2.32 10-pixel partial circle
+ 1.42 1.18 1.00 1.00 1.42 100-pixel partial circle
+ 1.92 1.85 1.01 1.01 1.89 10-pixel wide partial circle
+ 1.73 1.67 1.00 1.00 1.73 100-pixel wide partial circle
+ 1.36 1.95 1.00 1.00 2.64 1-pixel solid circle
+ 2.02 1.37 1.00 1.00 2.03 10-pixel solid circle
+ 1.19 1.09 1.00 1.00 1.19 100-pixel solid circle
+ 1.02 0.99 1.00 1.00 1.01 500-pixel solid circle
+ 1.74 1.28 1.00 0.88 1.73 10-pixel fill chord partial circle
+ 1.31 1.13 1.00 1.00 1.31 100-pixel fill chord partial circle
+ 1.67 1.31 1.03 1.03 1.72 10-pixel fill slice partial circle
+ 1.30 1.13 1.00 1.00 1.28 100-pixel fill slice partial circle
+ 2.45 1.49 1.01 1.00 2.71 10-pixel ellipse
+ 1.22 1.10 1.00 1.00 1.22 100-pixel ellipse
+ 1.09 1.04 1.00 1.00 1.09 500-pixel ellipse
+ 1.90 1.28 1.00 1.00 1.89 100-pixel dashed ellipse
+ 1.62 1.24 0.96 0.97 1.61 100-pixel double-dashed ellipse
+ 2.43 1.50 1.00 1.00 2.42 10-pixel wide ellipse
+ 1.61 1.28 1.03 1.03 1.60 100-pixel wide ellipse
+ 1.08 1.05 1.00 1.00 1.08 500-pixel wide ellipse
+ 1.93 1.88 1.00 1.00 1.88 100-pixel wide dashed ellipse
+ 1.94 1.89 1.01 1.00 1.94 100-pixel wide double-dashed ellipse
+ 2.31 1.48 1.00 1.00 2.67 10-pixel partial ellipse
+ 1.38 1.17 1.00 1.00 1.38 100-pixel partial ellipse
+ 2.00 1.85 0.98 0.97 1.98 10-pixel wide partial ellipse
+ 1.89 1.86 1.00 1.00 1.89 100-pixel wide partial ellipse
+ 3.49 1.60 1.00 1.00 3.65 10-pixel filled ellipse
+ 1.67 1.26 1.00 1.00 1.67 100-pixel filled ellipse
+ 1.06 1.04 1.00 1.00 1.06 500-pixel filled ellipse
+ 2.38 1.43 1.01 1.00 2.32 10-pixel fill chord partial ellipse
+ 2.06 1.30 1.00 1.00 2.05 100-pixel fill chord partial ellipse
+ 2.27 1.41 1.00 1.00 2.27 10-pixel fill slice partial ellipse
+ 1.98 1.33 1.00 0.97 1.97 100-pixel fill slice partial ellipse
+ 57.46 1.99 1.01 1.00 114.92 Fill 1x1 equivalent triangle
+ 56.94 1.98 1.01 1.00 73.89 Fill 10x10 equivalent triangle
+ 6.07 1.75 1.00 1.00 6.07 Fill 100x100 equivalent triangle
+ 51.12 1.98 1.00 1.00 102.81 Fill 1x1 trapezoid
+ 51.42 1.82 1.01 1.00 94.89 Fill 10x10 trapezoid
+ 6.47 1.80 1.00 1.00 6.44 Fill 100x100 trapezoid
+ 1.56 1.28 1.00 0.99 1.56 Fill 300x300 trapezoid
+ 51.27 1.97 0.96 0.97 102.54 Fill 1x1 stippled trapezoid (8x8 stipple)
+ 51.73 2.00 1.02 1.02 67.92 Fill 10x10 stippled trapezoid (8x8 stipple)
+ 5.36 1.72 1.00 1.00 5.36 Fill 100x100 stippled trapezoid (8x8 stipple)
+ 1.54 1.26 1.00 1.00 1.59 Fill 300x300 stippled trapezoid (8x8 stipple)
+ 51.41 1.94 1.01 1.00 102.82 Fill 1x1 opaque stippled trapezoid (8x8 stipple)
+ 50.71 1.95 0.99 1.00 65.44 Fill 10x10 opaque stippled trapezoid (8x8...
+ 5.33 1.73 1.00 1.00 5.36 Fill 100x100 opaque stippled trapezoid (8x8...
+ 1.58 1.25 1.00 1.00 1.58 Fill 300x300 opaque stippled trapezoid (8x8...
+ 51.56 1.96 0.99 0.90 103.68 Fill 1x1 tiled trapezoid (4x4 tile)
+ 51.59 1.99 1.01 1.01 62.25 Fill 10x10 tiled trapezoid (4x4 tile)
+ 5.38 1.72 1.00 1.00 5.38 Fill 100x100 tiled trapezoid (4x4 tile)
+ 1.54 1.25 1.00 0.99 1.58 Fill 300x300 tiled trapezoid (4x4 tile)
+ 51.70 1.98 1.01 1.01 103.98 Fill 1x1 stippled trapezoid (17x15 stipple)
+ 44.86 1.97 1.00 1.00 44.86 Fill 10x10 stippled trapezoid (17x15 stipple)
+ 2.74 1.56 1.00 1.00 2.73 Fill 100x100 stippled trapezoid (17x15 stipple)
+ 1.29 1.14 1.00 1.00 1.27 Fill 300x300 stippled trapezoid (17x15 stipple)
+ 51.41 1.96 0.96 0.95 103.39 Fill 1x1 opaque stippled trapezoid (17x15...
+ 45.14 1.96 1.01 1.00 45.14 Fill 10x10 opaque stippled trapezoid (17x15...
+ 2.68 1.56 1.00 1.00 2.68 Fill 100x100 opaque stippled trapezoid (17x15...
+ 1.26 1.10 1.00 1.00 1.28 Fill 300x300 opaque stippled trapezoid (17x15...
+ 51.13 1.97 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (17x15 tile)
+ 47.58 1.96 1.00 1.00 47.86 Fill 10x10 tiled trapezoid (17x15 tile)
+ 2.74 1.56 1.00 1.00 2.74 Fill 100x100 tiled trapezoid (17x15 tile)
+ 1.29 1.14 1.00 1.00 1.28 Fill 300x300 tiled trapezoid (17x15 tile)
+ 51.13 1.97 0.99 0.97 103.39 Fill 1x1 stippled trapezoid (161x145 stipple)
+ 45.14 1.97 1.00 1.00 44.29 Fill 10x10 stippled trapezoid (161x145 stipple)
+ 3.02 1.77 1.12 1.12 3.38 Fill 100x100 stippled trapezoid (161x145 stipple)
+ 1.31 1.13 1.00 1.00 1.30 Fill 300x300 stippled trapezoid (161x145 stipple)
+ 51.27 1.97 1.00 1.00 103.10 Fill 1x1 opaque stippled trapezoid (161x145...
+ 45.01 1.97 1.00 1.00 45.01 Fill 10x10 opaque stippled trapezoid (161x145...
+ 2.67 1.56 1.00 1.00 2.69 Fill 100x100 opaque stippled trapezoid (161x145..
+ 1.29 1.13 1.00 1.01 1.27 Fill 300x300 opaque stippled trapezoid (161x145..
+ 51.41 1.96 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (161x145 tile)
+ 45.01 1.96 0.98 1.00 45.01 Fill 10x10 tiled trapezoid (161x145 tile)
+ 2.62 1.36 1.00 1.00 2.69 Fill 100x100 tiled trapezoid (161x145 tile)
+ 1.27 1.13 1.00 1.00 1.22 Fill 300x300 tiled trapezoid (161x145 tile)
+ 51.13 1.98 1.00 1.00 103.39 Fill 1x1 tiled trapezoid (216x208 tile)
+ 45.14 1.97 1.01 0.99 45.14 Fill 10x10 tiled trapezoid (216x208 tile)
+ 2.62 1.55 1.00 1.00 2.71 Fill 100x100 tiled trapezoid (216x208 tile)
+ 1.28 1.13 1.00 1.00 1.20 Fill 300x300 tiled trapezoid (216x208 tile)
+ 50.71 1.95 1.00 1.00 54.70 Fill 10x10 equivalent complex polygon
+ 5.51 1.71 0.96 0.98 5.47 Fill 100x100 equivalent complex polygons
+ 8.39 1.97 1.00 1.00 16.75 Fill 10x10 64-gon (Convex)
+ 8.38 1.83 1.00 1.00 8.43 Fill 100x100 64-gon (Convex)
+ 8.50 1.96 1.00 1.00 16.64 Fill 10x10 64-gon (Complex)
+ 8.26 1.83 1.00 1.00 8.35 Fill 100x100 64-gon (Complex)
+ 14.09 1.87 1.00 1.00 14.05 Char in 80-char line (6x13)
+ 11.91 1.87 1.00 1.00 11.95 Char in 70-char line (8x13)
+ 11.16 1.85 1.01 1.00 11.10 Char in 60-char line (9x15)
+ 10.09 1.78 1.00 1.00 10.09 Char16 in 40-char line (k14)
+ 6.15 1.75 1.00 1.00 6.31 Char16 in 23-char line (k24)
+ 11.92 1.90 1.03 1.03 11.88 Char in 80-char line (TR 10)
+ 8.18 1.78 1.00 0.99 8.17 Char in 30-char line (TR 24)
+ 42.83 1.44 1.01 1.00 42.11 Char in 20/40/20 line (6x13, TR 10)
+ 27.45 1.43 1.01 1.01 27.45 Char16 in 7/14/7 line (k14, k24)
+ 12.13 1.85 1.00 1.00 12.05 Char in 80-char image line (6x13)
+ 10.00 1.84 1.00 1.00 10.00 Char in 70-char image line (8x13)
+ 9.18 1.83 1.00 1.00 9.12 Char in 60-char image line (9x15)
+ 9.66 1.82 0.98 0.95 9.66 Char16 in 40-char image line (k14)
+ 5.82 1.72 1.00 1.00 5.99 Char16 in 23-char image line (k24)
+ 8.70 1.80 1.00 1.00 8.65 Char in 80-char image line (TR 10)
+ 4.67 1.66 1.00 1.00 4.67 Char in 30-char image line (TR 24)
+ 84.43 1.47 1.00 1.00 124.18 Scroll 10x10 pixels
+ 3.73 1.50 1.00 0.98 3.73 Scroll 100x100 pixels
+ 1.00 1.00 1.00 1.00 1.00 Scroll 500x500 pixels
+ 84.43 1.51 1.00 1.00 134.02 Copy 10x10 from window to window
+ 3.62 1.51 0.98 0.98 3.62 Copy 100x100 from window to window
+ 0.89 1.00 1.00 1.00 1.00 Copy 500x500 from window to window
+ 57.06 1.99 1.00 1.00 88.64 Copy 10x10 from pixmap to window
+ 2.49 2.00 1.00 1.00 2.48 Copy 100x100 from pixmap to window
+ 1.00 0.91 1.00 1.00 0.98 Copy 500x500 from pixmap to window
+ 2.04 1.01 1.00 1.00 2.03 Copy 10x10 from window to pixmap
+ 1.05 1.00 1.00 1.00 1.05 Copy 100x100 from window to pixmap
+ 1.00 1.00 0.93 1.00 1.04 Copy 500x500 from window to pixmap
+ 58.52 1.03 1.03 1.02 57.95 Copy 10x10 from pixmap to pixmap
+ 2.40 1.00 1.00 1.00 2.45 Copy 100x100 from pixmap to pixmap
+ 1.00 1.00 1.00 1.00 1.00 Copy 500x500 from pixmap to pixmap
+ 51.57 1.92 1.00 1.00 85.75 Copy 10x10 1-bit deep plane
+ 6.37 1.75 1.01 1.01 6.37 Copy 100x100 1-bit deep plane
+ 1.26 1.11 1.00 1.00 1.24 Copy 500x500 1-bit deep plane
+ 4.23 1.63 0.98 0.97 4.38 Copy 10x10 n-bit deep plane
+ 1.04 1.02 1.00 1.00 1.04 Copy 100x100 n-bit deep plane
+ 1.00 1.00 1.00 1.00 1.00 Copy 500x500 n-bit deep plane
+ 6.45 1.98 1.00 1.26 12.80 PutImage 10x10 square
+ 1.10 1.87 1.00 1.83 2.11 PutImage 100x100 square
+ 1.02 1.93 1.00 1.91 1.91 PutImage 500x500 square
+ 4.17 1.78 1.00 1.40 7.18 PutImage XY 10x10 square
+ 1.27 1.49 0.97 1.48 2.10 PutImage XY 100x100 square
+ 1.00 1.50 1.00 1.50 1.52 PutImage XY 500x500 square
+ 1.07 1.01 1.00 1.00 1.06 GetImage 10x10 square
+ 1.01 1.00 1.00 1.00 1.01 GetImage 100x100 square
+ 1.00 1.00 1.00 1.00 1.00 GetImage 500x500 square
+ 1.56 1.00 0.99 0.97 1.56 GetImage XY 10x10 square
+ 1.02 1.00 1.00 1.00 1.02 GetImage XY 100x100 square
+ 1.00 1.00 1.00 1.00 1.00 GetImage XY 500x500 square
+ 1.00 1.00 1.01 0.98 0.95 X protocol NoOperation
+ 1.02 1.03 1.04 1.03 1.00 QueryPointer
+ 1.03 1.02 1.04 1.03 1.00 GetProperty
+ 100.41 1.51 1.00 1.00 198.76 Change graphics context
+ 45.81 1.00 0.99 0.97 57.10 Create and map subwindows (4 kids)
+ 78.45 1.01 1.02 1.02 63.07 Create and map subwindows (16 kids)
+ 73.91 1.01 1.00 1.00 56.37 Create and map subwindows (25 kids)
+ 73.22 1.00 1.00 1.00 49.07 Create and map subwindows (50 kids)
+ 72.36 1.01 0.99 1.00 32.14 Create and map subwindows (75 kids)
+ 70.34 1.00 1.00 1.00 30.12 Create and map subwindows (100 kids)
+ 55.00 1.00 1.00 0.99 23.75 Create and map subwindows (200 kids)
+ 55.30 1.01 1.00 1.00 141.03 Create unmapped window (4 kids)
+ 55.38 1.01 1.01 1.00 163.25 Create unmapped window (16 kids)
+ 54.75 0.96 1.00 0.99 166.95 Create unmapped window (25 kids)
+ 54.83 1.00 1.00 0.99 178.81 Create unmapped window (50 kids)
+ 55.38 1.01 1.01 1.00 181.20 Create unmapped window (75 kids)
+ 55.38 1.01 1.01 1.00 181.20 Create unmapped window (100 kids)
+ 54.87 1.01 1.01 1.00 182.05 Create unmapped window (200 kids)
+ 28.13 1.00 1.00 1.00 30.75 Map window via parent (4 kids)
+ 36.14 1.01 1.01 1.01 32.58 Map window via parent (16 kids)
+ 26.13 1.00 0.98 0.95 29.85 Map window via parent (25 kids)
+ 40.07 1.00 1.01 1.00 27.57 Map window via parent (50 kids)
+ 23.26 0.99 1.00 1.00 18.23 Map window via parent (75 kids)
+ 22.91 0.99 1.00 0.99 16.52 Map window via parent (100 kids)
+ 27.79 1.00 1.00 0.99 12.50 Map window via parent (200 kids)
+ 22.35 1.00 1.00 1.00 56.19 Unmap window via parent (4 kids)
+ 9.57 1.00 0.99 1.00 89.78 Unmap window via parent (16 kids)
+ 80.77 1.01 1.00 1.00 103.85 Unmap window via parent (25 kids)
+ 96.34 1.00 1.00 1.00 116.06 Unmap window via parent (50 kids)
+ 99.72 1.00 1.00 1.00 124.93 Unmap window via parent (75 kids)
+ 112.36 1.00 1.00 1.00 125.27 Unmap window via parent (100 kids)
+ 105.41 1.00 1.00 0.99 120.00 Unmap window via parent (200 kids)
+ 51.29 1.03 1.02 1.02 74.19 Destroy window via parent (4 kids)
+ 86.75 0.99 0.99 0.99 116.87 Destroy window via parent (16 kids)
+ 106.43 1.01 1.01 1.01 127.49 Destroy window via parent (25 kids)
+ 120.34 1.01 1.01 1.00 140.11 Destroy window via parent (50 kids)
+ 126.67 1.00 0.99 0.99 145.00 Destroy window via parent (75 kids)
+ 126.11 1.01 1.01 1.00 140.56 Destroy window via parent (100 kids)
+ 128.57 1.01 1.00 1.00 137.91 Destroy window via parent (200 kids)
+ 16.04 0.88 1.00 1.00 20.36 Hide/expose window via popup (4 kids)
+ 19.04 1.01 1.00 1.00 23.48 Hide/expose window via popup (16 kids)
+ 19.22 1.00 1.00 1.00 20.44 Hide/expose window via popup (25 kids)
+ 17.41 1.00 0.91 0.97 17.68 Hide/expose window via popup (50 kids)
+ 17.29 1.01 1.00 1.01 17.07 Hide/expose window via popup (75 kids)
+ 16.74 1.00 1.00 1.00 16.17 Hide/expose window via popup (100 kids)
+ 10.30 1.00 1.00 1.00 10.51 Hide/expose window via popup (200 kids)
+ 16.48 1.01 1.00 1.00 26.05 Move window (4 kids)
+ 17.01 0.95 1.00 1.00 23.97 Move window (16 kids)
+ 16.95 1.00 1.00 1.00 22.90 Move window (25 kids)
+ 16.05 1.01 1.00 1.00 21.32 Move window (50 kids)
+ 15.58 1.00 0.98 0.98 19.44 Move window (75 kids)
+ 14.98 1.02 1.03 1.03 18.17 Move window (100 kids)
+ 10.90 1.01 1.01 1.00 12.68 Move window (200 kids)
+ 49.42 1.00 1.00 1.00 198.27 Moved unmapped window (4 kids)
+ 50.72 0.97 1.00 1.00 193.66 Moved unmapped window (16 kids)
+ 50.87 1.00 0.99 1.00 195.09 Moved unmapped window (25 kids)
+ 50.72 1.00 1.00 1.00 189.34 Moved unmapped window (50 kids)
+ 50.87 1.00 1.00 1.00 191.33 Moved unmapped window (75 kids)
+ 50.87 1.00 1.00 0.90 186.71 Moved unmapped window (100 kids)
+ 50.87 1.00 1.00 1.00 179.19 Moved unmapped window (200 kids)
+ 41.04 1.00 1.00 1.00 56.61 Move window via parent (4 kids)
+ 69.81 1.00 1.00 1.00 130.82 Move window via parent (16 kids)
+ 95.81 1.00 1.00 1.00 141.92 Move window via parent (25 kids)
+ 95.98 1.00 1.00 1.00 149.43 Move window via parent (50 kids)
+ 96.59 1.01 1.01 1.00 153.98 Move window via parent (75 kids)
+ 97.19 1.00 1.00 1.00 157.30 Move window via parent (100 kids)
+ 96.67 1.00 0.99 0.96 159.44 Move window via parent (200 kids)
+ 17.75 1.01 1.00 1.00 27.61 Resize window (4 kids)
+ 17.94 1.00 1.00 0.99 25.42 Resize window (16 kids)
+ 17.92 1.01 1.00 1.00 24.47 Resize window (25 kids)
+ 17.24 0.97 1.00 1.00 24.14 Resize window (50 kids)
+ 16.81 1.00 1.00 0.99 22.75 Resize window (75 kids)
+ 16.08 1.00 1.00 1.00 21.20 Resize window (100 kids)
+ 12.92 1.00 0.99 1.00 16.26 Resize window (200 kids)
+ 52.94 1.01 1.00 1.00 327.12 Resize unmapped window (4 kids)
+ 53.60 1.01 1.01 1.01 333.71 Resize unmapped window (16 kids)
+ 52.99 1.00 1.00 1.00 337.29 Resize unmapped window (25 kids)
+ 51.98 1.00 1.00 1.00 329.38 Resize unmapped window (50 kids)
+ 53.05 0.89 1.00 1.00 322.60 Resize unmapped window (75 kids)
+ 53.05 1.00 1.00 1.00 318.08 Resize unmapped window (100 kids)
+ 53.11 1.00 1.00 0.99 306.21 Resize unmapped window (200 kids)
+ 16.76 1.00 0.96 1.00 19.46 Circulate window (4 kids)
+ 17.24 1.00 1.00 0.97 16.24 Circulate window (16 kids)
+ 16.30 1.03 1.03 1.03 15.85 Circulate window (25 kids)
+ 13.45 1.00 1.00 1.00 14.90 Circulate window (50 kids)
+ 12.91 1.00 1.00 1.00 13.06 Circulate window (75 kids)
+ 11.30 0.98 1.00 1.00 11.03 Circulate window (100 kids)
+ 7.58 1.01 1.01 0.99 7.47 Circulate window (200 kids)
+ 1.01 1.01 0.98 1.00 0.95 Circulate Unmapped window (4 kids)
+ 1.07 1.07 1.01 1.07 1.02 Circulate Unmapped window (16 kids)
+ 1.04 1.09 1.06 1.05 0.97 Circulate Unmapped window (25 kids)
+ 1.04 1.23 1.20 1.18 1.05 Circulate Unmapped window (50 kids)
+ 1.18 1.53 1.19 1.45 1.24 Circulate Unmapped window (75 kids)
+ 1.08 1.02 1.01 1.74 1.01 Circulate Unmapped window (100 kids)
+ 1.01 1.12 0.98 0.91 0.97 Circulate Unmapped window (200 kids)
+
+
+
+ BB..22..88.. PPrrooffiilliinngg wwiitthh OOPPrrooffiillee
+
+ OProfile (available from http://oprofile.sourceforge.net/) is a
+ system-wide profiler for Linux systems that uses processor-level
+ counters to collect sampling data. OProfile can provide information
+ that is similar to that provided by gprof, but without the necessity
+ of recompiling the program with special instrumentation (i.e.,
+ OProfile can collect statistical profiling information about optimized
+ programs). A test harness was developed to collect OProfile data for
+ each x11perf test individually.
+
+
+ Test runs were performed using the RETIRED_INSNS counter on the AMD
+ Athlon and the CPU_CLK_HALTED counter on the Intel Pentium III (with a
+ test configuration different from the one described above). We have
+ examined OProfile output and have compared it with gprof output. This
+ investigation has not produced results that yield performance
+ increases in x11perf numbers.
+
+
+
+ BB..22..99.. XX TTeesstt SSuuiittee
+
+ The X Test Suite was run on the fully optimized DMX server using the
+ configuration described above. The following failures were noted:
+
+ XListPixmapFormats: Test 1 [1]
+ XChangeWindowAttributes: Test 32 [1]
+ XCreateWindow: Test 30 [1]
+ XFreeColors: Test 4 [3]
+ XCopyArea: Test 13, 17, 21, 25, 30 [2]
+ XCopyPlane: Test 11, 15, 27, 31 [2]
+ XSetFontPath: Test 4 [1]
+ XChangeKeyboardControl: Test 9, 10 [1]
+
+ [1] Previously documented errors expected from the Xinerama
+ implementation (see Phase I discussion).
+ [2] Newly noted errors that have been verified as expected
+ behavior of the Xinerama implementation.
+ [3] Newly noted error that has been verified as a Xinerama
+ implementation bug.
+
+
+
+ BB..33.. PPhhaassee IIIIII
+
+ During the third phase of development, support was provided for the
+ following extensions: SHAPE, RENDER, XKEYBOARD, XInput.
+
+
+ BB..33..11.. SSHHAAPPEE
+
+ The SHAPE extension is supported. Test applications (e.g., xeyes and
+ oclock) and window managers that make use of the SHAPE extension will
+ work as expected.
+
+
+ BB..33..22.. RREENNDDEERR
+
+ The RENDER extension is supported. The version included in the DMX
+ CVS tree is version 0.2, and this version is fully supported by Xdmx.
+ Applications using only version 0.2 functions will work correctly;
+ however, some apps that make use of functions from later versions do
+ not properly check the extension's major/minor version numbers. These
+ apps will fail with a Bad Implementation error when using post-version
+ 0.2 functions. This is expected behavior. When the DMX CVS tree is
+ updated to include newer versions of RENDER, support for these newer
+ functions will be added to the DMX X server.
+
+
+ BB..33..33.. XXKKEEYYBBOOAARRDD
+
+ The XKEYBOARD extension is supported. If present on the back-end X
+ servers, the XKEYBOARD extension will be used to obtain information
+ about the type of the keyboard for initialization. Otherwise, the
+ keyboard will be initialized using defaults. Note that this departs
+ from older behavior: when Xdmx is compiled without XKEYBOARD support,
+ the map from the back-end X server will be preserved. With XKEYBOARD
+ support, the map is not preserved because better information and
+ control of the keyboard is available.
+
+
+ BB..33..44.. XXIInnppuutt
+
+ The XInput extension is supported. Any device can be used as a core
+ device and be used as an XInput extension device, with the exception
+ of core devices on the back-end servers. This limitation is present
+ because cursor handling on the back-end requires that the back-end
+ cursor sometimes track the Xdmx core cursor -- behavior that is
+ incompatible with using the back-end pointer as a non-core device.
+
+
+ Currently, back-end extension devices are not available as Xdmx
+ extension devices, but this limitation should be removed in the
+ future.
+
+
+ To demonstrate the XInput extension, and to provide more examples for
+ low-level input device driver writers, USB device drivers have been
+ written for mice (usb-mou), keyboards (usb-kbd), and non-mouse/non-
+ keyboard USB devices (usb-oth). Please see the man page for
+ information on Linux kernel drivers that are required for using these
+ Xdmx drivers.
+
+
+ BB..33..55.. DDPPMMSS
+
+ The DPMS extension is exported but does not do anything at this time.
+
+
+ BB..33..66.. OOtthheerr EExxtteennssiioonnss
+
+ The LBX, SECURITY, XC-APPGROUP, and XFree86-Bigfont extensions do not
+ require any special Xdmx support and have been exported.
+
+
+ The BIG-REQUESTS, DEC-XTRAP, DOUBLE-BUFFER, Extended-Visual-
+ Information, FontCache, GLX, MIT-SCREEN-SAVER, MIT-SHM, MIT-SUNDRY-
+ NONSTANDARD, RECORD, SECURITY, SGI-GLX, SYNC, TOG-CUP, X-Resource, XC-
+ MISC, XFree86-DGA, XFree86-DRI, XFree86-Misc,
+ XFree86-VidModeExtension, and XVideo extensions are _n_o_t supported at
+ this time, but will be evaluated for inclusion in future DMX releases.
+ SSeeee bbeellooww ffoorr aaddddiittiioonnaall wwoorrkk oonn eexxtteennssiioonnss aafftteerr PPhhaassee IIIIII..
+
+
+ BB..44.. PPhhaassee IIVV
+
+ BB..44..11.. MMoovviinngg ttoo XXFFrreeee8866 44..33..00
+
+ For Phase IV, the recent release of XFree86 4.3.0 (27 February 2003)
+ was merged onto the dmx.sourceforge.net CVS trunk and all work is
+ proceeding using this tree.
+
+
+ BB..44..22.. EExxtteennssiioonnss
+
+ BB..44..22..11.. XXCC--MMIISSCC ((ssuuppppoorrtteedd))
+
+ XC-MISC is used internally by the X library to recycle XIDs from the X
+ server. This is important for long-running X server sessions. Xdmx
+ supports this extension. The X Test Suite passed and failed the exact
+ same tests before and after this extension was enabled.
+
+
+ BB..44..22..22.. EExxtteennddeedd--VViissuuaall--IInnffoorrmmaattiioonn ((ssuuppppoorrtteedd))
+
+ The Extended-Visual-Information extension provides a method for an X
+ client to obtain detailed visual information. Xdmx supports this
+ extension. It was tested using the hw/dmx/examples/evi example
+ program. NNoottee tthhaatt tthhiiss eexxtteennssiioonn iiss nnoott XXiinneerraammaa--aawwaarree -- it will
+ return visual information for each screen even though Xinerama is
+ causing the X server to export a single logical screen.
+
+
+ BB..44..22..33.. RREESS ((ssuuppppoorrtteedd))
+
+ The X-Resource extension provides a mechanism for a client to obtain
+ detailed information about the resources used by other clients. This
+ extension was tested with the hw/dmx/examples/res program. The X Test
+ Suite passed and failed the exact same tests before and after this
+ extension was enabled.
+
+
+ BB..44..22..44.. BBIIGG--RREEQQUUEESSTTSS ((ssuuppppoorrtteedd))
+
+ This extension enables the X11 protocol to handle requests longer than
+ 262140 bytes. The X Test Suite passed and failed the exact same tests
+ before and after this extension was enabled.
+
+
+ BB..44..22..55.. XXSSYYNNCC ((ssuuppppoorrtteedd))
+
+ This extension provides facilities for two different X clients to
+ synchronize their requests. This extension was minimally tested with
+ xdpyinfo and the X Test Suite passed and failed the exact same tests
+ before and after this extension was enabled.
+
+
+ BB..44..22..66.. XXTTEESSTT,, RREECCOORRDD,, DDEECC--XXTTRRAAPP ((ssuuppppoorrtteedd)) aanndd XXTTeessttEExxtteennssiioonn11
+ ((nnoott ssuuppppoorrtteedd))
+
+ The XTEST and RECORD extension were developed by the X Consortium for
+ use in the X Test Suite and are supported as a standard in the X11R6
+ tree. They are also supported in Xdmx. When X Test Suite tests that
+ make use of the XTEST extension are run, Xdmx passes and fails exactly
+ the same tests as does a standard XFree86 X server. When the rcrdtest
+ test (a part of the X Test Suite that verifies the RECORD extension)
+ is run, Xdmx passes and fails exactly the same tests as does a
+ standard XFree86 X server.
+
+
+ There are two older XTEST-like extensions: DEC-XTRAP and
+ XTestExtension1. The XTestExtension1 extension was developed for use
+ by the X Testing Consortium for use with a test suite that eventually
+ became (part of?) the X Test Suite. Unlike XTEST, which only allows
+ events to be sent to the server, the XTestExtension1 extension also
+ allowed events to be recorded (similar to the RECORD extension). The
+ second is the DEC-XTRAP extension that was developed by the Digital
+ Equipment Corporation.
+
+
+ The DEC-XTRAP extension is available from Xdmx and has been tested
+ with the xtrap* tools which are distributed as standard X11R6 clients.
+
+
+ The XTestExtension1 is _n_o_t supported because it does not appear to be
+ used by any modern X clients (the few that support it also support
+ XTEST) and because there are no good methods available for testing
+ that it functions correctly (unlike XTEST and DEC-XTRAP, the code for
+ XTestExtension1 is not part of the standard X server source tree, so
+ additional testing is important).
+
+
+ Most of these extensions are documented in the X11R6 source tree.
+ Further, several original papers exist that this author was unable to
+ locate -- for completeness and historical interest, citations are
+ provide:
+
+ XXRREECCOORRDD
+ Martha Zimet. Extending X For Recording. 8th Annual X Technical
+ Conference Boston, MA January 24-26, 1994.
+
+ DDEECC--XXTTRRAAPP
+ Dick Annicchiarico, Robert Chesler, Alan Jamison. XTrap
+ Architecture. Digital Equipment Corporation, July 1991.
+
+ XXTTeessttEExxtteennssiioonn11
+ Larry Woestman. X11 Input Synthesis Extension Proposal. Hewlett
+ Packard, November 1991.
+
+
+ BB..44..22..77.. MMIITT--MMIISSCC ((nnoott ssuuppppoorrtteedd))
+
+ The MIT-MISC extension is used to control a bug-compatibility flag
+ that provides compatibility with xterm programs from X11R1 and X11R2.
+ There does not appear to be a single client available that makes use
+ of this extension and there is not way to verify that it works
+ correctly. The Xdmx server does _n_o_t support MIT-MISC.
+
+
+ BB..44..22..88.. SSCCRREEEENNSSAAVVEERR ((nnoott ssuuppppoorrtteedd))
+
+ This extension provides special support for the X screen saver. It
+ was tested with beforelight, which appears to be the only client that
+ works with it. When Xinerama was not active, beforelight behaved as
+ expected. However, when Xinerama was active, beforelight did not
+ behave as expected. Further, when this extension is not active,
+ xscreensaver (a widely-used X screen saver program) did not behave as
+ expected. Since this extension is not Xinerama-aware and is not
+ commonly used with expected results by clients, we have left this
+ extension disabled at this time.
+
+ BB..44..22..99.. GGLLXX ((ssuuppppoorrtteedd))
+
+ The GLX extension provides OpenGL and GLX windowing support. In Xdmx,
+ the extension is called glxProxy, and it is Xinerama aware. It works
+ by either feeding requests forward through Xdmx to each of the back-
+ end servers or handling them locally. All rendering requests are
+ handled on the back-end X servers. This code was donated to the DMX
+ project by SGI. For the X Test Suite results comparison, see below.
+
+
+ BB..44..22..1100.. RREENNDDEERR ((ssuuppppoorrtteedd))
+
+ The X Rendering Extension (RENDER) provides support for digital image
+ composition. Geometric and text rendering are supported. RENDER is
+ partially Xinerama-aware, with text and the most basic compositing
+ operator; however, its higher level primitives (triangles, triangle
+ strips, and triangle fans) are not yet Xinerama-aware. The RENDER
+ extension is still under development, and is currently at version 0.8.
+ Additional support will be required in DMX as more primitives and/or
+ requests are added to the extension.
+
+
+ There is currently no test suite for the X Rendering Extension;
+ however, there has been discussion of developing a test suite as the
+ extension matures. When that test suite becomes available, additional
+ testing can be performed with Xdmx. The X Test Suite passed and
+ failed the exact same tests before and after this extension was
+ enabled.
+
+
+ BB..44..22..1111.. SSuummmmaarryy
+
+ To summarize, the following extensions are currently supported: BIG-
+ REQUESTS, DEC-XTRAP, DMX, DPMS, Extended-Visual-Information, GLX, LBX,
+ RECORD, RENDER, SECURITY, SHAPE, SYNC, X-Resource, XC-APPGROUP, XC-
+ MISC, XFree86-Bigfont, XINERAMA, XInputExtension, XKEYBOARD, and
+ XTEST.
+
+
+ The following extensions are _n_o_t supported at this time: DOUBLE-
+ BUFFER, FontCache, MIT-SCREEN-SAVER, MIT-SHM, MIT-SUNDRY-NONSTANDARD,
+ TOG-CUP, XFree86-DGA, XFree86-Misc, XFree86-VidModeExtension,
+ XTestExtensionExt1, and XVideo.
+
+
+ BB..44..33.. AAddddiittiioonnaall TTeessttiinngg wwiitthh tthhee XX TTeesstt SSuuiittee
+
+ BB..44..33..11.. XXFFrreeee8866 wwiitthhoouutt XXTTEESSTT
+
+ After the release of XFree86 4.3.0, we retested the XFree86 X server
+ with and without using the XTEST extension. When the XTEST extension
+ was _n_o_t used for testing, the XFree86 4.3.0 server running on our
+ usual test system with a Radeon VE card reported unexpected failures
+ in the following tests:
+
+ XListPixmapFormats: Test 1
+ XChangeKeyboardControl: Tests 9, 10
+ XGetDefault: Test 5
+ XRebindKeysym: Test 1
+
+
+
+ BB..44..33..22.. XXFFrreeee8866 wwiitthh XXTTEESSTT
+
+ When using the XTEST extension, the XFree86 4.3.0 server reported the
+ following errors:
+
+ XListPixmapFormats: Test 1
+ XChangeKeyboardControl: Tests 9, 10
+ XGetDefault: Test 5
+ XRebindKeysym: Test 1
+
+ XAllowEvents: Tests 20, 21, 24
+ XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
+ XGrabKey: Test 8
+ XSetPointerMapping: Test 3
+ XUngrabButton: Test 4
+
+
+
+ While these errors may be important, they will probably be fixed
+ eventually in the XFree86 source tree. We are particularly interested
+ in demonstrating that the Xdmx server does not introduce additional
+ failures that are not known Xinerama failures.
+
+
+ BB..44..33..33.. XXddmmxx wwiitthh XXTTEESSTT,, wwiitthhoouutt XXiinneerraammaa,, wwiitthhoouutt GGLLXX
+
+ Without Xinerama, but using the XTEST extension, the following errors
+ were reported from Xdmx (note that these are the same as for the
+ XFree86 4.3.0, except that XGetDefault no longer fails):
+
+ XListPixmapFormats: Test 1
+ XChangeKeyboardControl: Tests 9, 10
+ XRebindKeysym: Test 1
+
+ XAllowEvents: Tests 20, 21, 24
+ XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
+ XGrabKey: Test 8
+ XSetPointerMapping: Test 3
+ XUngrabButton: Test 4
+
+
+
+ BB..44..33..44.. XXddmmxx wwiitthh XXTTEESSTT,, wwiitthh XXiinneerraammaa,, wwiitthhoouutt GGLLXX
+
+ With Xinerama, using the XTEST extension, the following errors were
+ reported from Xdmx:
+
+ XListPixmapFormats: Test 1
+ XChangeKeyboardControl: Tests 9, 10
+ XRebindKeysym: Test 1
+
+ XAllowEvents: Tests 20, 21, 24
+ XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
+ XGrabKey: Test 8
+ XSetPointerMapping: Test 3
+ XUngrabButton: Test 4
+
+ XCopyPlane: Tests 13, 22, 31 (well-known XTEST/Xinerama interaction issue)
+ XDrawLine: Test 67
+ XDrawLines: Test 91
+ XDrawSegments: Test 68
+
+
+
+ Note that the first two sets of errors are the same as for the XFree86
+ 4.3.0 server, and that the XCopyPlane error is a well-known error
+ resulting from an XTEST/Xinerama interaction when the request crosses
+ a screen boundary. The XDraw* errors are resolved when the tests are
+ run individually and they do not cross a screen boundary. We will
+ investigate these errors further to determine their cause.
+
+
+ BB..44..33..55.. XXddmmxx wwiitthh XXTTEESSTT,, wwiitthh XXiinneerraammaa,, wwiitthh GGLLXX
+
+ With GLX enabled, using the XTEST extension, the following errors were
+ reported from Xdmx (these results are from early during the Phase IV
+ development, but were confirmed with a late Phase IV snapshot):
+
+ XListPixmapFormats: Test 1
+ XChangeKeyboardControl: Tests 9, 10
+ XRebindKeysym: Test 1
+
+ XAllowEvents: Tests 20, 21, 24
+ XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
+ XGrabKey: Test 8
+ XSetPointerMapping: Test 3
+ XUngrabButton: Test 4
+
+ XClearArea: Test 8
+ XCopyArea: Tests 4, 5, 11, 14, 17, 23, 25, 27, 30
+ XCopyPlane: Tests 6, 7, 10, 19, 22, 31
+ XDrawArcs: Tests 89, 100, 102
+ XDrawLine: Test 67
+ XDrawSegments: Test 68
+
+
+ Note that the first two sets of errors are the same as for the XFree86
+ 4.3.0 server, and that the third set has different failures than when
+ Xdmx does not include GLX support. Since the GLX extension adds new
+ visuals to support GLX's visual configs and the X Test Suite runs
+ tests over the entire set of visuals, additional rendering tests were
+ run and presumably more of them crossed a screen boundary. This con-
+ clusion is supported by the fact that nearly all of the rendering
+ errors reported are resolved when the tests are run individually and
+ they do no cross a screen boundary.
+
+
+ Further, when hardware rendering is disabled on the back-end displays,
+ many of the errors in the third set are eliminated, leaving only:
+
+ XClearArea: Test 8
+ XCopyArea: Test 4, 5, 11, 14, 17, 23, 25, 27, 30
+ XCopyPlane: Test 6, 7, 10, 19, 22, 31
+
+
+
+ BB..44..33..66.. CCoonncclluussiioonn
+
+ We conclude that all of the X Test Suite errors reported for Xdmx are
+ the result of errors in the back-end X server or the Xinerama
+ implementation. Further, all of these errors that can be reasonably
+ fixed at the Xdmx layer have been. (Where appropriate, we have
+ submitted patches to the XFree86 and Xinerama upstream maintainers.)
+
+
+ BB..44..44.. DDyynnaammiicc RReeccoonnffiigguurraattiioonn
+
+ During this development phase, dynamic reconfiguration support was
+ added to DMX. This support allows an application to change the
+ position and offset of a back-end server's screen. For example, if
+ the application would like to shift a screen slightly to the left, it
+ could query Xdmx for the screen's <x,y> position and then dynamically
+ reconfigure that screen to be at position <x+10,y>. When a screen is
+ dynamically reconfigured, input handling and a screen's root window
+ dimensions are adjusted as needed. These adjustments are transparent
+ to the user.
+
+
+ BB..44..44..11.. DDyynnaammiicc rreeccoonnffiigguurraattiioonn eexxtteennssiioonn
+
+ The application interface to DMX's dynamic reconfiguration is through
+ a function in the DMX extension library:
+
+ Bool DMXReconfigureScreen(Display *dpy, int screen, int x, int y)
+
+
+ where _d_p_y is DMX server's display, _s_c_r_e_e_n is the number of the screen
+ to be reconfigured, and _x and _y are the new upper, left-hand coordi-
+ nates of the screen to be reconfigured.
+
+
+ The coordinates are not limited other than as required by the X
+ protocol, which limits all coordinates to a signed 16 bit number. In
+ addition, all coordinates within a screen must also be legal values.
+ Therefore, setting a screen's upper, left-hand coordinates such that
+ the right or bottom edges of the screen is greater than 32,767 is
+ illegal.
+
+
+ BB..44..44..22.. BBoouunnddiinngg bbooxx
+
+ When the Xdmx server is started, a bounding box is calculated from the
+ screens' layout given either on the command line or in the
+ configuration file. This bounding box is currently fixed for the
+ lifetime of the Xdmx server.
+
+
+ While it is possible to move a screen outside of the bounding box, it
+ is currently not possible to change the dimensions of the bounding
+ box. For example, it is possible to specify coordinates of
+ <-100,-100> for the upper, left-hand corner of the bounding box, which
+ was previously at coordinates <0,0>. As expected, the screen is moved
+ down and to the right; however, since the bounding box is fixed, the
+ left side and upper portions of the screen exposed by the
+ reconfiguration are no longer accessible on that screen. Those
+ inaccessible regions are filled with black.
+
+
+ This fixed bounding box limitation will be addressed in a future
+ development phase.
+
+
+ BB..44..44..33.. SSaammppllee aapppplliiccaattiioonnss
+
+ An example of where this extension is useful is in setting up a video
+ wall. It is not always possible to get everything perfectly aligned,
+ and sometimes the positions are changed (e.g., someone might bump into
+ a projector). Instead of physically moving projectors or monitors, it
+ is now possible to adjust the positions of the back-end server's
+ screens using the dynamic reconfiguration support in DMX.
+
+
+ Other applications, such as automatic setup and calibration tools, can
+ make use of dynamic reconfiguration to correct for projector alignment
+ problems, as long as the projectors are still arranged rectilinearly.
+ Horizontal and vertical keystone correction could be applied to
+ projectors to correct for non-rectilinear alignment problems; however,
+ this must be done external to Xdmx.
+
+
+ A sample test program is included in the DMX server's examples
+ directory to demonstrate the interface and how an application might
+ use dynamic reconfiguration. See dmxreconfig.c for details.
+
+
+ BB..44..44..44.. AAddddiittiioonnaall nnootteess
+
+ In the original development plan, Phase IV was primarily devoted to
+ adding OpenGL support to DMX; however, SGI became interested in the
+ DMX project and developed code to support OpenGL/GLX. This code was
+ later donated to the DMX project and integrated into the DMX code
+ base, which freed the DMX developers to concentrate on dynamic
+ reconfiguration (as described above).
+
+
+ BB..44..55.. DDooxxyyggeenn ddooccuummeennttaattiioonn
+
+ Doxygen is an open-source (GPL) documentation system for generating
+ browseable documentation from stylized comments in the source code.
+ We have placed all of the Xdmx server and DMX protocol source code
+ files under Doxygen so that comprehensive documentation for the Xdmx
+ source code is available in an easily browseable format.
+
+
+ BB..44..66.. VVaallggrriinndd
+
+ Valgrind, an open-source (GPL) memory debugger for Linux, was used to
+ search for memory management errors. Several memory leaks were
+ detected and repaired. The following errors were not addressed:
+
+ 1. When the X11 transport layer sends a reply to the client, only
+ those fields that are required by the protocol are filled in --
+ unused fields are left as uninitialized memory and are therefore
+ noted by valgrind. These instances are not errors and were not
+ repaired.
+
+ 2. At each server generation, glxInitVisuals allocates memory that is
+ never freed. The amount of memory lost each generation
+ approximately equal to 128 bytes for each back-end visual. Because
+ the code involved is automatically generated, this bug has not been
+ fixed and will be referred to SGI.
+
+ 3. At each server generation, dmxRealizeFont calls XLoadQueryFont,
+ which allocates a font structure that is not freed.
+ dmxUnrealizeFont can free the font structure for the first screen,
+ but cannot free it for the other screens since they are already
+ closed by the time dmxUnrealizeFont could free them. The amount of
+ memory lost each generation is approximately equal to 80 bytes per
+ font per back-end. When this bug is fixed in the the X server's
+ device-independent (dix) code, DMX will be able to properly free
+ the memory allocated by XLoadQueryFont.
+
+
+ BB..44..77.. RRAATTSS
+
+ RATS (Rough Auditing Tool for Security) is an open-source (GPL)
+ security analysis tool that scans source code for common security-
+ related programming errors (e.g., buffer overflows and TOCTOU races).
+ RATS was used to audit all of the code in the hw/dmx directory and all
+ "High" notations were checked manually. The code was either re-
+ written to eliminate the warning, or a comment containing "RATS" was
+ inserted on the line to indicate that a human had checked the code.
+ Unrepaired warnings are as follows:
+
+ 1. Fixed-size buffers are used in many areas, but code has been added
+ to protect against buffer overflows (e.g., XmuSnprint). The only
+ instances that have not yet been fixed are in config/xdmxconfig.c
+ (which is not part of the Xdmx server) and input/usb-common.c.
+
+ 2. vprintf and vfprintf are used in the logging routines. In general,
+ all uses of these functions (e.g., dmxLog) provide a constant
+ format string from a trusted source, so the use is relatively
+ benign.
+
+ 3. glxProxy/glxscreens.c uses getenv and strcat. The use of these
+ functions is safe and will remain safe as long as ExtensionsString
+ is longer then GLXServerExtensions (ensuring this may not be ovious
+ to the casual programmer, but this is in automatically generated
+ code, so we hope that the generator enforces this constraint).
+
+
+
diff --git a/hw/dmx/doc/dmx.txt b/hw/dmx/doc/dmx.txt
deleted file mode 100644
index 568c751..0000000
--- a/hw/dmx/doc/dmx.txt
+++ /dev/null
@@ -1,2989 +0,0 @@
- Distributed Multihead X design
- Kevin E. Martin, David H. Dawes, and Rickard E. Faith
-
- 29 June 2004 (created 25 July 2001)
-
- This document covers the motivation, background, design, and implemen-
- tation of the distributed multihead X (DMX) system. It is a living
- document and describes the current design and implementation details
- of the DMX system. As the project progresses, this document will be
- continually updated to reflect the changes in the code and/or design.
- _C_o_p_y_r_i_g_h_t _2_0_0_1 _b_y _V_A _L_i_n_u_x _S_y_s_t_e_m_s_, _I_n_c_._, _F_r_e_m_o_n_t_, _C_a_l_i_f_o_r_n_i_a_. _C_o_p_y_-
- _r_i_g_h_t _2_0_0_1_-_2_0_0_4 _b_y _R_e_d _H_a_t_, _I_n_c_._, _R_a_l_e_i_g_h_, _N_o_r_t_h _C_a_r_o_l_i_n_a
-
- ______________________________________________________________________
-
- Table of Contents
-
-
-
- 1. Introduction
- 1.1 The Distributed Multihead X Server
- 1.2 Layout of Paper
-
- 2. Development plan
- 2.1 Bootstrap code
- 2.2 Input device handling
- 2.3 Output device handling
- 2.3.1 Initialization
- 2.3.2 Handling rendering requests
- 2.4 Optimizing DMX
- 2.5 DMX X extension support
- 2.6 Common X extension support
- 2.7 OpenGL support
-
- 3. Current issues
- 3.1 Fonts
- 3.2 Zero width rendering primitives
- 3.3 Output scaling
- 3.4 Per-screen colormaps
-
- A. Background
- A.1 Core input device handling
- A.1.1 InitInput()
- A.1.2 InitAndStartDevices()
- A.1.3 devReadInput()
- A.1.4 ProcessInputEvents()
- A.1.5 DisableDevice()
- A.1.6 CloseDevice()
- A.1.7 LegalModifier()
- A.2 Output handling
- A.2.1 InitOutput()
- A.2.2 AddScreen()
- A.2.3 ScreenInit()
- A.2.4 CloseScreen()
- A.2.5 GC operations
- A.2.6 Xnest
- A.2.7 Shadow framebuffer
- A.3 Xinerama
- A.3.1 Xinerama-specific changes to the DIX code
- A.3.2 Xinerama-specific changes to the MI code
- A.3.3 Intercepted DIX core requests
-
- B. Development Results
- B.1 Phase I
- B.1.1 Scope
- B.1.2 Results
- B.1.3 X Test Suite
- B.1.3.1 Introduction
- B.1.3.2 Expected Failures for a Single Head
- B.1.3.3 Expected Failures for Xinerama
- B.1.3.4 Additional Failures from Xdmx
- B.1.3.5 Summary and Future Work
- B.1.4 Fonts
- B.1.5 Performance
- B.1.6 Pixmaps
- B.2 Phase II
- B.2.1 Moving from XFree86 4.1.99.1 to 4.2.0.0
- B.2.2 Global changes
- B.2.3 XSync() Batching
- B.2.4 Offscreen Optimization
- B.2.5 Lazy Window Creation Optimization
- B.2.6 Subdividing Rendering Primitives
- B.2.7 Summary of x11perf Data
- B.2.8 Profiling with OProfile
- B.2.9 X Test Suite
- B.3 Phase III
- B.3.1 SHAPE
- B.3.2 RENDER
- B.3.3 XKEYBOARD
- B.3.4 XInput
- B.3.5 DPMS
- B.3.6 Other Extensions
- B.4 Phase IV
- B.4.1 Moving to XFree86 4.3.0
- B.4.2 Extensions
- B.4.2.1 XC-MISC (supported)
- B.4.2.2 Extended-Visual-Information (supported)
- B.4.2.3 RES (supported)
- B.4.2.4 BIG-REQUESTS (supported)
- B.4.2.5 XSYNC (supported)
- B.4.2.6 XTEST, RECORD, DEC-XTRAP (supported) and XTestExtension1 (not supported)
- B.4.2.7 MIT-MISC (not supported)
- B.4.2.8 SCREENSAVER (not supported)
- B.4.2.9 GLX (supported)
- B.4.2.10 RENDER (supported)
- B.4.2.11 Summary
- B.4.3 Additional Testing with the X Test Suite
- B.4.3.1 XFree86 without XTEST
- B.4.3.2 XFree86 with XTEST
- B.4.3.3 Xdmx with XTEST, without Xinerama, without GLX
- B.4.3.4 Xdmx with XTEST, with Xinerama, without GLX
- B.4.3.5 Xdmx with XTEST, with Xinerama, with GLX
- B.4.3.6 Conclusion
- B.4.4 Dynamic Reconfiguration
- B.4.4.1 Dynamic reconfiguration extension
- B.4.4.2 Bounding box
- B.4.4.3 Sample applications
- B.4.4.4 Additional notes
- B.4.5 Doxygen documentation
- B.4.6 Valgrind
- B.4.7 RATS
-
-
- ______________________________________________________________________
-
- 11.. IInnttrroodduuccttiioonn
-
- 11..11.. TThhee DDiissttrriibbuutteedd MMuullttiihheeaadd XX SSeerrvveerr
-
- Current Open Source multihead solutions are limited to a single
- physical machine. A single X server controls multiple display
- devices, which can be arranged as independent heads or unified into a
- single desktop (with Xinerama). These solutions are limited to the
- number of physical devices that can co-exist in a single machine
- (e.g., due to the number of AGP/PCI slots available for graphics
- cards). Thus, large tiled displays are not currently possible. The
- work described in this paper will eliminate the requirement that the
- display devices reside in the same physical machine. This will be
- accomplished by developing a front-end proxy X server that will
- control multiple back-end X servers that make up the large display.
-
-
- The overall structure of the distributed multihead X (DMX) project is
- as follows: A single front-end X server will act as a proxy to a set
- of back-end X servers, which handle all of the visible rendering. X
- clients will connect to the front-end server just as they normally
- would to a regular X server. The front-end server will present an
- abstracted view to the client of a single large display. This will
- ensure that all standard X clients will continue to operate without
- modification (limited, as always, by the visuals and extensions
- provided by the X server). Clients that are DMX-aware will be able to
- use an extension to obtain information about the back-end servers
- (e.g., for placement of pop-up windows, window alignments by the
- window manager, etc.).
-
-
- The architecture of the DMX server is divided into two main sections:
- input (e.g., mouse and keyboard events) and output (e.g., rendering
- and windowing requests). Each of these are describe briefly below,
- and the rest of this design document will describe them in greater
- detail.
-
-
- The DMX server can receive input from three general types of input
- devices: "local" devices that are physically attached to the machine
- on which DMX is running, "backend" devices that are physically
- attached to one or more of the back-end X servers (and that generate
- events via the X protocol stream from the backend), and "console"
- devices that can be abstracted from any non-back-end X server.
- Backend and console devices are treated differently because the
- pointer device on the back-end X server also controls the location of
- the hardware X cursor. Full support for XInput extension devices is
- provided.
-
-
- Rendering requests will be accepted by the front-end server; however,
- rendering to visible windows will be broken down as needed and sent to
- the appropriate back-end server(s) via X11 library calls for actual
- rendering. The basic framework will follow a Xnest-style approach.
- GC state will be managed in the front-end server and sent to the
- appropriate back-end server(s) as required. Pixmap rendering will (at
- least initially) be handled by the front-end X server. Windowing
- requests (e.g., ordering, mapping, moving, etc.) will handled in the
- front-end server. If the request requires a visible change, the
- windowing operation will be translated into requests for the
- appropriate back-end server(s). Window state will be mirrored in the
- back-end server(s) as needed.
-
-
- 11..22.. LLaayyoouutt ooff PPaappeerr
-
- The next section describes the general development plan that was
- actually used for implementation. The final section discusses
- outstanding issues at the conclusion of development. The first
- appendix provides low-level technical detail that may be of interest
- to those intimately familiar with the X server architecture. The
- final appendix describes the four phases of development that were
- performed during the first two years of development.
-
-
- The final year of work was divided into 9 tasks that are not described
- in specific sections of this document. The major tasks during that
- time were the enhancement of the reconfiguration ability added in
- Phase IV, addition of support for a dynamic number of back-end
- displays (instead of a hard-coded limit), and the support for back-end
- display and input removal and addition. This work is mentioned in
- this paper, but is not covered in detail.
-
-
- 22.. DDeevveellooppmmeenntt ppllaann
-
- This section describes the development plan from approximately June
- 2001 through July 2003.
-
-
-
- 22..11.. BBoooottssttrraapp ccooddee
-
- To allow for rapid development of the DMX server by multiple
- developers during the first development stage, the problem will be
- broken down into three tasks: the overall DMX framework, back-end
- rendering services and input device handling services. However,
- before the work begins on these tasks, a simple framework that each
- developer could use was implemented to bootstrap the development
- effort. This framework renders to a single back-end server and
- provides dummy input devices (i.e., the keyboard and mouse). The
- simple back-end rendering service was implemented using the shadow
- framebuffer support currently available in the XFree86 environment.
-
-
- Using this bootstrapping framework, each developer has been able to
- work on each of the tasks listed above independently as follows: the
- framework will be extended to handle arbitrary back-end server
- configurations; the back-end rendering services will be transitioned
- to the more efficient Xnest-style implementation; and, an input device
- framework to handle various input devices via the input extension will
- be developed.
-
-
- Status: The boot strap code is complete.
-
-
-
- 22..22.. IInnppuutt ddeevviiccee hhaannddlliinngg
-
- An X server (including the front-end X server) requires two core input
- devices -- a keyboard and a pointer (mouse). These core devices are
- handled and required by the core X11 protocol. Additional types of
- input devices may be attached and utilized via the XInput extension.
- These are usually referred to as ``XInput extension devices'',
-
-
- There are some options as to how the front-end X server gets its core
- input devices:
-
-
- 1. Local Input. The physical input devices (e.g., keyboard and mouse)
- can be attached directly to the front-end X server. In this case,
- the keyboard and mouse on the machine running the front-end X
- server will be used. The front-end will have drivers to read the
- raw input from those devices and convert it into the required X
- input events (e.g., key press/release, pointer button
- press/release, pointer motion). The front-end keyboard driver will
- keep track of keyboard properties such as key and modifier
- mappings, autorepeat state, keyboard sound and led state.
- Similarly the front-end pointer driver will keep track if pointer
- properties such as the button mapping and movement acceleration
- parameters. With this option, input is handled fully in the front-
- end X server, and the back-end X servers are used in a display-only
- mode. This option was implemented and works for a limited number
- of Linux-specific devices. Adding additional local input devices
- for other architectures is expected to be relatively simple.
-
-
- The following options are available for implementing local input
- devices:
-
-
- a. The XFree86 X server has modular input drivers that could be
- adapted for this purpose. The mouse driver supports a wide
- range of mouse types and interfaces, as well as a range of
- Operating System platforms. The keyboard driver in XFree86 is
- not currently as modular as the mouse driver, but could be made
- so. The XFree86 X server also has a range of other input
- drivers for extended input devices such as tablets and touch
- screens. Unfortunately, the XFree86 drivers are generally
- complex, often simultaneously providing support for multiple
- devices across multiple architectures; and rely so heavily on
- XFree86-specific helper-functions, that this option was not
- pursued.
-
-
- b. The kdrive X server in XFree86 has built-in drivers that support
- PS/2 mice and keyboard under Linux. The mouse driver can
- indirectly handle other mouse types if the Linux utility gpm is
- used as to translate the native mouse protocol into PS/2 mouse
- format. These drivers could be adapted and built in to the
- front-end X server if this range of hardware and OS support is
- sufficient. While much simpler than the XFree86 drivers, the
- kdrive drivers were not used for the DMX implementation.
-
- c. Reimplementation of keyboard and mouse drivers from scratch for
- the DMX framework. Because keyboard and mouse drivers are
- relatively trivial to implement, this pathway was selected.
- Other drivers in the X source tree were referenced, and
- significant contributions from other drivers are noted in the
- DMX source code.
-
-
- 2. Backend Input. The front-end can make use of the core input
- devices attached to one or more of the back-end X servers. Core
- input events from multiple back-ends are merged into a single input
- event stream. This can work sanely when only a single set of input
- devices is used at any given time. The keyboard and pointer state
- will be handled in the front-end, with changes propagated to the
- back-end servers as needed. This option was implemented and works
- well. Because the core pointer on a back-end controls the hardware
- mouse on that back-end, core pointers cannot be treated as XInput
- extension devices. However, all back-end XInput extensions devices
- can be mapped to either DMX core or DMX XInput extension devices.
-
- 3. Console Input. The front-end server could create a console window
- that is displayed on an X server independent of the back-end X
- servers. This console window could display things like the
- physical screen layout, and the front-end could get its core input
- events from events delivered to the console window. This option
- was implemented and works well. To help the human navigate, window
- outlines are also displayed in the console window. Further,
- console windows can be used as either core or XInput extension
- devices.
-
- 4. Other options were initially explored, but they were all partial
- subsets of the options listed above and, hence, are irrelevant.
-
-
- Although extended input devices are not specifically mentioned in the
- Distributed X requirements, the options above were all implemented so
- that XInput extension devices were supported.
-
-
- The bootstrap code (Xdmx) had dummy input devices, and these are still
- supported in the final version. These do the necessary initialization
- to satisfy the X server's requirements for core pointer and keyboard
- devices, but no input events are ever generated.
-
-
- Status: The input code is complete. Because of the complexity of the
- XFree86 input device drivers (and their heavy reliance on XFree86
- infrastructure), separate low-level device drivers were implemented
- for Xdmx. The following kinds of drivers are supported (in general,
- the devices can be treated arbitrarily as "core" input devices or as
- XInput "extension" devices; and multiple instances of different kinds
- of devices can be simultaneously available):
-
- 1. A "dummy" device drive that never generates events.
-
- 2. "Local" input is from the low-level hardware on which the Xdmx
- binary is running. This is the only area where using the XFree86
- driver infrastructure would have been helpful, and then only
- partially, since good support for generic USB devices does not yet
- exist in XFree86 (in any case, XFree86 and kdrive driver code was
- used where possible). Currently, the following local devices are
- supported under Linux (porting to other operating systems should be
- fairly straightforward):
-
- +o Linux keyboard
-
- +o Linux serial mouse (MS)
-
- +o Linux PS/2 mouse
-
- +o USB keyboard
-
- +o USB mouse
-
- +o USB generic device (e.g., joystick, gamepad, etc.)
-
-
- 3. "Backend" input is taken from one or more of the back-end displays.
- In this case, events are taken from the back-end X server and are
- converted to Xdmx events. Care must be taken so that the sprite
- moves properly on the display from which input is being taken.
-
- 4. "Console" input is taken from an X window that Xdmx creates on the
- operator's display (i.e., on the machine running the Xdmx binary).
- When the operator's mouse is inside the console window, then those
- events are converted to Xdmx events. Several special features are
- available: the console can display outlines of windows that are on
- the Xdmx display (to facilitate navigation), the cursor can be
- confined to the console, and a "fine" mode can be activated to
- allow very precise cursor positioning.
-
-
-
- 22..33.. OOuuttppuutt ddeevviiccee hhaannddlliinngg
-
- The output of the DMX system displays rendering and windowing requests
- across multiple screens. The screens are typically arranged in a grid
- such that together they represent a single large display.
-
-
- The output section of the DMX code consists of two parts. The first
- is in the front-end proxy X server (Xdmx), which accepts client
- connections, manages the windows, and potentially renders primitives
- but does not actually display any of the drawing primitives. The
- second part is the back-end X server(s), which accept commands from
- the front-end server and display the results on their screens.
-
-
- 22..33..11.. IInniittiiaalliizzaattiioonn
-
- The DMX front-end must first initialize its screens by connecting to
- each of the back-end X servers and collecting information about each
- of these screens. However, the information collected from the back-
- end X servers might be inconsistent. Handling these cases can be
- difficult and/or inefficient. For example, a two screen system has
- one back-end X server running at 16bpp while the second is running at
- 32bpp. Converting rendering requests (e.g., XPutImage() or
- XGetImage() requests) to the appropriate bit depth can be very time
- consuming. Analyzing these cases to determine how or even if it is
- possible to handle them is required. The current Xinerama code
- handles many of these cases (e.g., in PanoramiXConsolidate()) and will
- be used as a starting point. In general, the best solution is to use
- homogeneous X servers and display devices. Using back-end servers
- with the same depth is a requirement of the final DMX implementation.
-
-
- Once this screen consolidation is finished, the relative position of
- each back-end X server's screen in the unified screen is initialized.
- A full-screen window is opened on each of the back-end X servers, and
- the cursor on each screen is turned off. The final DMX implementation
- can also make use of a partial-screen window, or multiple windows per
- back-end screen.
-
-
- 22..33..22.. HHaannddlliinngg rreennddeerriinngg rreeqquueessttss
-
- After initialization, X applications connect to the front-end server.
- There are two possible implementations of how rendering and windowing
- requests are handled in the DMX system:
-
-
- 1. A shadow framebuffer is used in the front-end server as the render
- target. In this option, all protocol requests are completely
- handled in the front-end server. All state and resources are
- maintained in the front-end including a shadow copy of the entire
- framebuffer. The framebuffers attached to the back-end servers are
- updated by XPutImage() calls with data taken directly from the
- shadow framebuffer.
-
-
- This solution suffers from two main problems. First, it does not
- take advantage of any accelerated hardware available in the system.
- Second, the size of the XPutImage() calls can be quite large and
- thus will be limited by the bandwidth available.
-
-
- The initial DMX implementation used a shadow framebuffer by
- default.
-
-
- 2. Rendering requests are sent to each back-end server for handling
- (as is done in the Xnest server described above). In this option,
- certain protocol requests are handled in the front-end server and
- certain requests are repackaged and then sent to the back-end
- servers. The framebuffer is distributed across the multiple back-
- end servers. Rendering to the framebuffer is handled on each back-
- end and can take advantage of any acceleration available on the
- back-end servers' graphics display device. State is maintained
- both in the front and back-end servers.
-
-
- This solution suffers from two main drawbacks. First, protocol
- requests are sent to all back-end servers -- even those that will
- completely clip the rendering primitive -- which wastes bandwidth
- and processing time. Second, state is maintained both in the
- front- and back-end servers. These drawbacks are not as severe as
- in option 1 (above) and can either be overcome through
- optimizations or are acceptable. Therefore, this option will be
- used in the final implementation.
-
-
- The final DMX implementation defaults to this mechanism, but also
- supports the shadow framebuffer mechanism. Several optimizations
- were implemented to eliminate the drawbacks of the default
- mechanism. These optimizations are described the section below and
- in Phase II of the Development Results (see appendix).
-
-
-
- Status: Both the shadow framebuffer and Xnest-style code is complete.
-
-
-
- 22..44.. OOppttiimmiizziinngg DDMMXX
-
- Initially, the Xnest-style solution's performance will be measured and
- analyzed to determine where the performance bottlenecks exist. There
- are four main areas that will be addressed.
-
-
- First, to obtain reasonable interactivity with the first development
- phase, XSync() was called after each protocol request. The XSync()
- function flushes any pending protocol requests. It then waits for the
- back-end to process the request and send a reply that the request has
- completed. This happens with each back-end server and performance
- greatly suffers. As a result of the way XSync() is called in the
- first development phase, the batching that the X11 library performs is
- effectively defeated. The XSync() call usage will be analyzed and
- optimized by batching calls and performing them at regular intervals,
- except where interactivity will suffer (e.g., on cursor movements).
-
-
- Second, the initial Xnest-style solution described above sends the
- repackaged protocol requests to all back-end servers regardless of
- whether or not they would be completely clipped out. The requests
- that are trivially rejected on the back-end server wastes the limited
- bandwidth available. By tracking clipping changes in the DMX X
- server's windowing code (e.g., by opening, closing, moving or resizing
- windows), we can determine whether or not back-end windows are visible
- so that trivial tests in the front-end server's GC ops drawing
- functions can eliminate these unnecessary protocol requests.
-
-
- Third, each protocol request will be analyzed to determine if it is
- possible to break the request into smaller pieces at display
- boundaries. The initial ones to be analyzed are put and get image
- requests since they will require the greatest bandwidth to transmit
- data between the front and back-end servers. Other protocol requests
- will be analyzed and those that will benefit from breaking them into
- smaller requests will be implemented.
-
-
- Fourth, an extension is being considered that will allow font glyphs
- to be transferred from the front-end DMX X server to each back-end
- server. This extension will permit the front-end to handle all font
- requests and eliminate the requirement that all back-end X servers
- share the exact same fonts as the front-end server. We are
- investigating the feasibility of this extension during this
- development phase.
-
-
- Other potential optimizations will be determined from the performance
- analysis.
-
- Please note that in our initial design, we proposed optimizing BLT
- operations (e.g., XCopyArea() and window moves) by developing an
- extension that would allow individual back-end servers to directly
- copy pixel data to other back-end servers. This potential
- optimization was in response to the simple image movement
- implementation that required potentially many calls to GetImage() and
- PutImage(). However, the current Xinerama implementation handles
- these BLT operations differently. Instead of copying data to and from
- screens, they generate expose events -- just as happens in the case
- when a window is moved from off a screen to on screen. This approach
- saves the limited bandwidth available between front and back-end
- servers and is being standardized with Xinerama. It also eliminates
- the potential setup problems and security issues resulting from having
- each back-end server open connections to all other back-end servers.
- Therefore, we suggest accepting Xinerama's expose event solution.
-
-
- Also note that the approach proposed in the second and third
- optimizations might cause backing store algorithms in the back-end to
- be defeated, so a DMX X server configuration flag will be added to
- disable these optimizations.
-
-
- Status: The optimizations proposed above are complete. It was
- determined that the using the xfs font server was sufficient and
- creating a new mechanism to pass glyphs was redundant; therefore, the
- fourth optimization proposed above was not included in DMX.
-
-
-
- 22..55.. DDMMXX XX eexxtteennssiioonn ssuuppppoorrtt
-
- The DMX X server keeps track of all the windowing information on the
- back-end X servers, but does not currently export this information to
- any client applications. An extension will be developed to pass the
- screen information and back-end window IDs to DMX-aware clients.
- These clients can then use this information to directly connect to and
- render to the back-end windows. Bypassing the DMX X server allows
- DMX-aware clients to break up complex rendering requests on their own
- and send them directly to the windows on the back-end server's
- screens. An example of a client that can make effective use of this
- extension is Chromium.
-
-
- Status: The extension, as implemented, is fully documented in "Client-
- to-Server DMX Extension to the X Protocol". Future changes might be
- required based on feedback and other proposed enhancements to DMX.
- Currently, the following facilities are supported:
-
- 1. Screen information (clipping rectangle for each screen relative to
- the virtual screen)
-
- 2. Window information (window IDs and clipping information for each
- back-end window that corresponds to each DMX window)
-
- 3. Input device information (mappings from DMX device IDs to back-end
- device IDs)
-
- 4. Force window creation (so that a client can override the server-
- side lazy window creation optimization)
-
- 5. Reconfiguration (so that a client can request that a screen
- position be changed)
-
- 6. Addition and removal of back-end servers and back-end and console
- inputs.
- 22..66.. CCoommmmoonn XX eexxtteennssiioonn ssuuppppoorrtt
-
- The XInput, XKeyboard and Shape extensions are commonly used
- extensions to the base X11 protocol. XInput allows multiple and non-
- standard input devices to be accessed simultaneously. These input
- devices can be connected to either the front-end or back-end servers.
- XKeyboard allows much better keyboard mappings control. Shape adds
- support for arbitrarily shaped windows and is used by various window
- managers. Nearly all potential back-end X servers make these
- extensions available, and support for each one will be added to the
- DMX system.
-
-
- In addition to the extensions listed above, support for the X
- Rendering extension (Render) is being developed. Render adds digital
- image composition to the rendering model used by the X Window System.
- While this extension is still under development by Keith Packard of
- HP, support for the current version will be added to the DMX system.
-
-
- Support for the XTest extension was added during the first development
- phase.
-
-
- Status: The following extensions are supported and are discussed in
- more detail in Phase IV of the Development Results (see appendix):
- BIG-REQUESTS, DEC-XTRAP, DMX, DPMS, Extended-Visual-Information, GLX,
- LBX, RECORD, RENDER, SECURITY, SHAPE, SYNC, X-Resource, XC-APPGROUP,
- XC-MISC, XFree86-Bigfont, XINERAMA, XInputExtension, XKEYBOARD, and
- XTEST.
-
-
- 22..77.. OOppeennGGLL ssuuppppoorrtt
-
- OpenGL support using the Mesa code base exists in XFree86 release 4
- and later. Currently, the direct rendering infrastructure (DRI)
- provides accelerated OpenGL support for local clients and
- unaccelerated OpenGL support (i.e., software rendering) is provided
- for non-local clients.
-
-
- The single head OpenGL support in XFree86 4.x will be extended to use
- the DMX system. When the front and back-end servers are on the same
- physical hardware, it is possible to use the DRI to directly render to
- the back-end servers. First, the existing DRI will be extended to
- support multiple display heads, and then to support the DMX system.
- OpenGL rendering requests will be direct rendering to each back-end X
- server. The DRI will request the screen layout (either from the
- existing Xinerama extension or a DMX-specific extension). Support for
- synchronized swap buffers will also be added (on hardware that
- supports it). Note that a single front-end server with a single back-
- end server on the same physical machine can emulate accelerated
- indirect rendering.
-
-
- When the front and back-end servers are on different physical hardware
- or are using non-XFree86 4.x X servers, a mechanism to render
- primitives across the back-end servers will be provided. There are
- several options as to how this can be implemented.
-
-
- 1. The existing OpenGL support in each back-end server can be used by
- repackaging rendering primitives and sending them to each back-end
- server. This option is similar to the unoptimized Xnest-style
- approach mentioned above. Optimization of this solution is beyond
- the scope of this project and is better suited to other distributed
- rendering systems.
-
- 2. Rendering to a pixmap in the front-end server using the current
- XFree86 4.x code, and then displaying to the back-ends via calls to
- XPutImage() is another option. This option is similar to the
- shadow frame buffer approach mentioned above. It is slower and
- bandwidth intensive, but has the advantage that the back-end
- servers are not required to have OpenGL support.
-
-
- These, and other, options will be investigated in this phase of the
- work.
-
-
- Work by others have made Chromium DMX-aware. Chromium will use the
- DMX X protocol extension to obtain information about the back-end
- servers and will render directly to those servers, bypassing DMX.
-
-
- Status: OpenGL support by the glxProxy extension was implemented by
- SGI and has been integrated into the DMX code base.
-
-
-
- 33.. CCuurrrreenntt iissssuueess
-
- In this sections the current issues are outlined that require further
- investigation.
-
-
- 33..11.. FFoonnttss
-
- The font path and glyphs need to be the same for the front-end and
- each of the back-end servers. Font glyphs could be sent to the back-
- end servers as necessary but this would consume a significant amount
- of available bandwidth during font rendering for clients that use many
- different fonts (e.g., Netscape). Initially, the font server (xfs)
- will be used to provide the fonts to both the front-end and back-end
- servers. Other possibilities will be investigated during development.
-
-
- 33..22.. ZZeerroo wwiiddtthh rreennddeerriinngg pprriimmiittiivveess
-
- To allow pixmap and on-screen rendering to be pixel perfect, all back-
- end servers must render zero width primitives exactly the same as the
- front-end renders the primitives to pixmaps. For those back-end
- servers that do not exactly match, zero width primitives will be
- automatically converted to one width primitives. This can be handled
- in the front-end server via the GC state.
-
-
- 33..33.. OOuuttppuutt ssccaalliinngg
-
- With very large tiled displays, it might be difficult to read the
- information on the standard X desktop. In particular, the cursor can
- be easily lost and fonts could be difficult to read. Automatic
- primitive scaling might prove to be very useful. We will investigate
- the possibility of scaling the cursor and providing a set of alternate
- pre-scaled fonts to replace the standard fonts that many applications
- use (e.g., fixed). Other options for automatic scaling will also be
- investigated.
-
-
-
- 33..44.. PPeerr--ssccrreeeenn ccoolloorrmmaappss
-
- Each screen's default colormap in the set of back-end X servers should
- be able to be adjusted via a configuration utility. This support is
- would allow the back-end screens to be calibrated via custom gamma
- tables. On 24-bit systems that support a DirectColor visual, this
- type of correction can be accommodated. One possible implementation
- would be to advertise to X client of the DMX server a TrueColor visual
- while using DirectColor visuals on the back-end servers to implement
- this type of color correction. Other options will be investigated.
-
-
- AA.. BBaacckkggrroouunndd
-
- This section describes the existing Open Source architectures that can
- be used to handle multiple screens and upon which this development
- project is based. This section was written before the implementation
- was finished, and may not reflect actual details of the
- implementation. It is left for historical interest only.
-
-
- AA..11.. CCoorree iinnppuutt ddeevviiccee hhaannddlliinngg
-
- The following is a description of how core input devices are handled
- by an X server.
-
-
- AA..11..11.. IInniittIInnppuutt(())
-
- InitInput() is a DDX function that is called at the start of each
- server generation from the X server's main() function. Its purpose is
- to determine what input devices are connected to the X server,
- register them with the DIX and MI layers, and initialize the input
- event queue. InitInput() does not have a return value, but the X
- server will abort if either a core keyboard device or a core pointer
- device are not registered. Extended input (XInput) devices can also
- be registered in InitInput().
-
-
- InitInput() usually has implementation specific code to determine
- which input devices are available. For each input device it will be
- using, it calls AddInputDevice():
-
-
- AAddddIInnppuuttDDeevviiccee(())
- This DIX function allocates the device structure, registers a
- callback function (which handles device init, close, on and
- off), and returns the input handle, which can be treated as
- opaque. It is called once for each input device.
-
-
- Once input handles for core keyboard and core pointer devices have
- been obtained from AddInputDevice(), they are registered as core
- devices by calling RegisterPointerDevice() and
- RegisterKeyboardDevice(). Each of these should be called once. If
- both core devices are not registered, then the X server will exit with
- a fatal error when it attempts to start the input devices in
- InitAndStartDevices(), which is called directly after InitInput() (see
- below).
-
-
- RReeggiisstteerr{{PPooiinntteerr,,KKeeyybbooaarrdd}}DDeevviiccee(())
- These DIX functions take a handle returned from AddInputDevice()
- and initialize the core input device fields in inputInfo, and
- initialize the input processing and grab functions for each core
- input device.
- The core pointer device is then registered with the miPointer code
- (which does the high level cursor handling). While this registration
- is not necessary for correct miPointer operation in the current
- XFree86 code, it is still done mostly for compatibility reasons.
-
-
- mmiiRReeggiisstteerrPPooiinntteerrDDeevviiccee(())
- This MI function registers the core pointer's input handle with
- with the miPointer code.
-
-
- The final part of InitInput() is the initialization of the input event
- queue handling. In most cases, the event queue handling provided in
- the MI layer is used. The primary XFree86 X server uses its own event
- queue handling to support some special cases related to the XInput
- extension and the XFree86-specific DGA extension. For our purposes,
- the MI event queue handling should be suitable. It is initialized by
- calling mieqInit():
-
-
- mmiieeqqIInniitt(())
- This MI function initializes the MI event queue for the core
- devices, and is passed the public component of the input handles
- for the two core devices.
-
-
- If a wakeup handler is required to deliver synchronous input events,
- it can be registered here by calling the DIX function
- RegisterBlockAndWakeupHandlers(). (See the devReadInput() description
- below.)
-
-
- AA..11..22.. IInniittAAnnddSSttaarrttDDeevviicceess(())
-
- InitAndStartDevices() is a DIX function that is called immediately
- after InitInput() from the X server's main() function. Its purpose is
- to initialize each input device that was registered with
- AddInputDevice(), enable each input device that was successfully
- initialized, and create the list of enabled input devices. Once each
- registered device is processed in this way, the list of enabled input
- devices is checked to make sure that both a core keyboard device and
- core pointer device were registered and successfully enabled. If not,
- InitAndStartDevices() returns failure, and results in the the X server
- exiting with a fatal error.
-
-
- Each registered device is initialized by calling its callback
- (dev->deviceProc) with the DEVICE_INIT argument:
-
-
- ((**ddeevv-->>ddeevviicceePPrroocc))((ddeevv,, DDEEVVIICCEE__IINNIITT))
- This function initializes the device structs with core
- information relevant to the device.
-
-
- For pointer devices, this means specifying the number of
- buttons, default button mapping, the function used to get motion
- events (usually miPointerGetMotionEvents()), the function used
- to change/control the core pointer motion parameters
- (acceleration and threshold), and the motion buffer size.
-
-
- For keyboard devices, this means specifying the keycode range,
- default keycode to keysym mapping, default modifier mapping, and
- the functions used to sound the keyboard bell and modify/control
- the keyboard parameters (LEDs, bell pitch and duration, key
- click, which keys are auto-repeating, etc).
-
-
- Each initialized device is enabled by calling EnableDevice():
-
-
- EEnnaabblleeDDeevviiccee(())
- EnableDevice() calls the device callback with DEVICE_ON:
-
- ((**ddeevv-->>ddeevviicceePPrroocc))((ddeevv,, DDEEVVIICCEE__OONN))
- This typically opens and initializes the relevant physical
- device, and when appropriate, registers the device's file
- descriptor (or equivalent) as a valid input source.
-
-
- EnableDevice() then adds the device handle to the X server's
- global list of enabled devices.
-
-
- InitAndStartDevices() then verifies that a valid core keyboard and
- pointer has been initialized and enabled. It returns failure if
- either are missing.
-
-
- AA..11..33.. ddeevvRReeaaddIInnppuutt(())
-
- Each device will have some function that gets called to read its
- physical input. These may be called in a number of different ways.
- In the case of synchronous I/O, they will be called from a DDX wakeup-
- handler that gets called after the server detects that new input is
- available. In the case of asynchronous I/O, they will be called from
- a (SIGIO) signal handler triggered when new input is available. This
- function should do at least two things: make sure that input events
- get enqueued, and make sure that the cursor gets moved for motion
- events (except if these are handled later by the driver's own event
- queue processing function, which cannot be done when using the MI
- event queue handling).
-
-
- Events are queued by calling mieqEnqueue():
-
-
- mmiieeqqEEnnqquueeuuee(())
- This MI function is used to add input events to the event queue.
- It is simply passed the event to be queued.
-
-
- The cursor position should be updated when motion events are enqueued,
- by calling either miPointerAbsoluteCursor() or miPointerDeltaCursor():
-
-
- mmiiPPooiinntteerrAAbbssoolluutteeCCuurrssoorr(())
- This MI function is used to move the cursor to the absolute
- coordinates provided.
-
- mmiiPPooiinntteerrDDeellttaaCCuurrssoorr(())
- This MI function is used to move the cursor relative to its
- current position.
-
-
- AA..11..44.. PPrroocceessssIInnppuuttEEvveennttss(())
-
- ProcessInputEvents() is a DDX function that is called from the X
- server's main dispatch loop when new events are available in the input
- event queue. It typically processes the enqueued events, and updates
- the cursor/pointer position. It may also do other DDX-specific event
- processing.
-
-
- Enqueued events are processed by mieqProcessInputEvents() and passed
- to the DIX layer for transmission to clients:
-
-
- mmiieeqqPPrroocceessssIInnppuuttEEvveennttss(())
- This function processes each event in the event queue, and
- passes it to the device's input processing function. The DIX
- layer provides default functions to do this processing, and they
- handle the task of getting the events passed back to the
- relevant clients.
-
- mmiiPPooiinntteerrUUppddaattee(())
- This function resynchronized the cursor position with the new
- pointer position. It also takes care of moving the cursor
- between screens when needed in multi-head configurations.
-
-
-
- AA..11..55.. DDiissaabblleeDDeevviiccee(())
-
- DisableDevice is a DIX function that removes an input device from the
- list of enabled devices. The result of this is that the device no
- longer generates input events. The device's data structures are kept
- in place, and disabling a device like this can be reversed by calling
- EnableDevice(). DisableDevice() may be called from the DDX when it is
- desirable to do so (e.g., the XFree86 server does this when VT
- switching). Except for special cases, this is not normally called for
- core input devices.
-
-
- DisableDevice() calls the device's callback function with DEVICE_OFF:
-
-
- ((**ddeevv-->>ddeevviicceePPrroocc))((ddeevv,, DDEEVVIICCEE__OOFFFF))
- This typically closes the relevant physical device, and when
- appropriate, unregisters the device's file descriptor (or
- equivalent) as a valid input source.
-
-
- DisableDevice() then removes the device handle from the X server's
- global list of enabled devices.
-
-
-
- AA..11..66.. CClloosseeDDeevviiccee(())
-
- CloseDevice is a DIX function that removes an input device from the
- list of available devices. It disables input from the device and
- frees all data structures associated with the device. This function
- is usually called from CloseDownDevices(), which is called from main()
- at the end of each server generation to close all input devices.
-
-
- CloseDevice() calls the device's callback function with DEVICE_CLOSE:
-
-
- ((**ddeevv-->>ddeevviicceePPrroocc))((ddeevv,, DDEEVVIICCEE__CCLLOOSSEE))
- This typically closes the relevant physical device, and when
- appropriate, unregisters the device's file descriptor (or
- equivalent) as a valid input source. If any device specific
- data structures were allocated when the device was initialized,
- they are freed here.
-
- CloseDevice() then frees the data structures that were allocated for
- the device when it was registered/initialized.
-
-
-
- AA..11..77.. LLeeggaallMMooddiiffiieerr(())
-
- LegalModifier() is a required DDX function that can be used to
- restrict which keys may be modifier keys. This seems to be present
- for historical reasons, so this function should simply return TRUE
- unconditionally.
-
-
-
- AA..22.. OOuuttppuutt hhaannddlliinngg
-
- The following sections describe the main functions required to
- initialize, use and close the output device(s) for each screen in the
- X server.
-
-
- AA..22..11.. IInniittOOuuttppuutt(())
-
- This DDX function is called near the start of each server generation
- from the X server's main() function. InitOutput()'s main purpose is
- to initialize each screen and fill in the global screenInfo structure
- for each screen. It is passed three arguments: a pointer to the
- screenInfo struct, which it is to initialize, and argc and argv from
- main(), which can be used to determine additional configuration
- information.
-
-
- The primary tasks for this function are outlined below:
-
-
- 1. PPaarrssee ccoonnffiigguurraattiioonn iinnffoo:: The first task of InitOutput() is to
- parses any configuration information from the configuration file.
- In addition to the XF86Config file, other configuration information
- can be taken from the command line. The command line options can
- be gathered either in InitOutput() or earlier in the
- ddxProcessArgument() function, which is called by
- ProcessCommandLine(). The configuration information determines the
- characteristics of the screen(s). For example, in the XFree86 X
- server, the XF86Config file specifies the monitor information, the
- screen resolution, the graphics devices and slots in which they are
- located, and, for Xinerama, the screens' layout.
-
- 2. IInniittiiaalliizzee ssccrreeeenn iinnffoo:: The next task is to initialize the screen-
- dependent internal data structures. For example, part of what the
- XFree86 X server does is to allocate its screen and pixmap private
- indices, probe for graphics devices, compare the probed devices to
- the ones listed in the XF86Config file, and add the ones that match
- to the internal xf86Screens[] structure.
-
- 3. SSeett ppiixxmmaapp ffoorrmmaattss:: The next task is to initialize the screenInfo's
- image byte order, bitmap bit order and bitmap scanline unit/pad.
- The screenInfo's pixmap format's depth, bits per pixel and scanline
- padding is also initialized at this stage.
-
- 4. UUnniiffyy ssccrreeeenn iinnffoo:: An optional task that might be done at this
- stage is to compare all of the information from the various screens
- and determines if they are compatible (i.e., if the set of screens
- can be unified into a single desktop). This task has potential to
- be useful to the DMX front-end server, if Xinerama's
- PanoramiXConsolidate() function is not sufficient.
-
- Once these tasks are complete, the valid screens are known and each of
- these screens can be initialized by calling AddScreen().
-
-
- AA..22..22.. AAddddSSccrreeeenn(())
-
- This DIX function is called from InitOutput(), in the DDX layer, to
- add each new screen to the screenInfo structure. The DDX screen
- initialization function and command line arguments (i.e., argc and
- argv) are passed to it as arguments.
-
-
- This function first allocates a new Screen structure and any privates
- that are required. It then initializes some of the fields in the
- Screen struct and sets up the pixmap padding information. Finally, it
- calls the DDX screen initialization function ScreenInit(), which is
- described below. It returns the number of the screen that were just
- added, or -1 if there is insufficient memory to add the screen or if
- the DDX screen initialization fails.
-
-
- AA..22..33.. SSccrreeeennIInniitt(())
-
- This DDX function initializes the rest of the Screen structure with
- either generic or screen-specific functions (as necessary). It also
- fills in various screen attributes (e.g., width and height in
- millimeters, black and white pixel values).
-
-
- The screen init function usually calls several functions to perform
- certain screen initialization functions. They are described below:
-
-
- {{mmii,,**ffbb}}SSccrreeeennIInniitt(())
- The DDX layer's ScreenInit() function usually calls another
- layer's ScreenInit() function (e.g., miScreenInit() or
- fbScreenInit()) to initialize the fallbacks that the DDX driver
- does not specifically handle.
-
-
- After calling another layer's ScreenInit() function, any screen-
- specific functions either wrap or replace the other layer's
- function pointers. If a function is to be wrapped, each of the
- old function pointers from the other layer are stored in a
- screen private area. Common functions to wrap are CloseScreen()
- and SaveScreen().
-
-
- mmiiIInniittiiaalliizzeeBBaacckkiinnggSSttoorree(())
- This MI function initializes the screen's backing storage
- functions, which are used to save areas of windows that are
- currently covered by other windows.
-
-
- mmiiDDCCIInniittiiaalliizzee(())
- This MI function initializes the MI cursor display structures
- and function pointers. If a hardware cursor is used, the DDX
- layer's ScreenInit() function will wrap additional screen and
- the MI cursor display function pointers.
-
-
- Another common task for ScreenInit() function is to initialize the
- output device state. For example, in the XFree86 X server, the
- ScreenInit() function saves the original state of the video card and
- then initializes the video mode of the graphics device.
-
- AA..22..44.. CClloosseeSSccrreeeenn(())
-
- This function restores any wrapped screen functions (and in particular
- the wrapped CloseScreen() function) and restores the state of the
- output device to its original state. It should also free any private
- data it created during the screen initialization.
-
-
- AA..22..55.. GGCC ooppeerraattiioonnss
-
- When the X server is requested to render drawing primitives, it does
- so by calling drawing functions through the graphics context's
- operation function pointer table (i.e., the GCOps functions). These
- functions render the basic graphics operations such as drawing
- rectangles, lines, text or copying pixmaps. Default routines are
- provided either by the MI layer, which draws indirectly through a
- simple span interface, or by the framebuffer layers (e.g., CFB, MFB,
- FB), which draw directly to a linearly mapped frame buffer.
-
-
- To take advantage of special hardware on the graphics device, specific
- GCOps functions can be replaced by device specific code. However,
- many times the graphics devices can handle only a subset of the
- possible states of the GC, so during graphics context validation,
- appropriate routines are selected based on the state and capabilities
- of the hardware. For example, some graphics hardware can accelerate
- single pixel width lines with certain dash patterns. Thus, for dash
- patterns that are not supported by hardware or for width 2 or greater
- lines, the default routine is chosen during GC validation.
-
-
- Note that some pointers to functions that draw to the screen are
- stored in the Screen structure. They include GetImage(), GetSpans(),
- PaintWindowBackground(), PaintWindowBorder(), CopyWindow() and
- RestoreAreas().
-
-
- AA..22..66.. XXnneesstt
-
- The Xnest X server is a special proxy X server that relays the X
- protocol requests that it receives to a ``real'' X server that then
- processes the requests and displays the results, if applicable. To
- the X applications, Xnest appears as if it is a regular X server.
- However, Xnest is both server to the X application and client of the
- real X server, which will actually handle the requests.
-
-
- The Xnest server implements all of the standard input and output
- initialization steps outlined above.
-
-
- IInniittOOuuttppuutt(())
- Xnest takes its configuration information from command line
- arguments via ddxProcessArguments(). This information includes
- the real X server display to connect to, its default visual
- class, the screen depth, the Xnest window's geometry, etc.
- Xnest then connects to the real X server and gathers visual,
- colormap, depth and pixmap information about that server's
- display, creates a window on that server, which will be used as
- the root window for Xnest.
-
-
- Next, Xnest initializes its internal data structures and uses
- the data from the real X server's pixmaps to initialize its own
- pixmap formats. Finally, it calls AddScreen(xnestOpenScreen,
- argc, argv) to initialize each of its screens.
- SSccrreeeennIInniitt(())
- Xnest's ScreenInit() function is called xnestOpenScreen(). This
- function initializes its screen's depth and visual information,
- and then calls miScreenInit() to set up the default screen
- functions. It then calls miInitializeBackingStore() and
- miDCInitialize() to initialize backing store and the software
- cursor. Finally, it replaces many of the screen functions with
- its own functions that repackage and send the requests to the
- real X server to which Xnest is attached.
-
-
- CClloosseeSSccrreeeenn(())
- This function frees its internal data structure allocations.
- Since it replaces instead of wrapping screen functions, there
- are no function pointers to unwrap. This can potentially lead
- to problems during server regeneration.
-
-
- GGCC ooppeerraattiioonnss
- The GC operations in Xnest are very simple since they leave all
- of the drawing to the real X server to which Xnest is attached.
- Each of the GCOps takes the request and sends it to the real X
- server using standard Xlib calls. For example, the X
- application issues a XDrawLines() call. This function turns
- into a protocol request to Xnest, which calls the
- xnestPolylines() function through Xnest's GCOps function pointer
- table. The xnestPolylines() function is only a single line,
- which calls XDrawLines() using the same arguments that were
- passed into it. Other GCOps functions are very similar. Two
- exceptions to the simple GCOps functions described above are the
- image functions and the BLT operations.
-
-
- The image functions, GetImage() and PutImage(), must use a
- temporary image to hold the image to be put of the image that
- was just grabbed from the screen while it is in transit to the
- real X server or the client. When the image has been
- transmitted, the temporary image is destroyed.
-
-
- The BLT operations, CopyArea() and CopyPlane(), handle not only
- the copy function, which is the same as the simple cases
- described above, but also the graphics exposures that result
- when the GC's graphics exposure bit is set to True. Graphics
- exposures are handled in a helper function,
- xnestBitBlitHelper(). This function collects the exposure
- events from the real X server and, if any resulting in regions
- being exposed, then those regions are passed back to the MI
- layer so that it can generate exposure events for the X
- application.
-
-
- The Xnest server takes its input from the X server to which it is
- connected. When the mouse is in the Xnest server's window, keyboard
- and mouse events are received by the Xnest server, repackaged and sent
- back to any client that requests those events.
-
-
- AA..22..77.. SShhaaddooww ffrraammeebbuuffffeerr
-
- The most common type of framebuffer is a linear array memory that maps
- to the video memory on the graphics device. However, accessing that
- video memory over an I/O bus (e.g., ISA or PCI) can be slow. The
- shadow framebuffer layer allows the developer to keep the entire
- framebuffer in main memory and copy it back to video memory at regular
- intervals. It also has been extended to handle planar video memory
- and rotated framebuffers.
-
-
- There are two main entry points to the shadow framebuffer code:
-
-
- sshhaaddoowwAAlllloocc((wwiiddtthh,, hheeiigghhtt,, bbpppp))
- This function allocates the in memory copy of the framebuffer of
- size width*height*bpp. It returns a pointer to that memory,
- which will be used by the framebuffer ScreenInit() code during
- the screen's initialization.
-
-
- sshhaaddoowwIInniitt((ppSSccrreeeenn,, uuppddaatteePPrroocc,, wwiinnddoowwPPrroocc))
- This function initializes the shadow framebuffer layer. It
- wraps several screen drawing functions, and registers a block
- handler that will update the screen. The updateProc is a
- function that will copy the damaged regions to the screen, and
- the windowProc is a function that is used when the entire linear
- video memory range cannot be accessed simultaneously so that
- only a window into that memory is available (e.g., when using
- the VGA aperture).
-
-
- The shadow framebuffer code keeps track of the damaged area of each
- screen by calculating the bounding box of all drawing operations that
- have occurred since the last screen update. Then, when the block
- handler is next called, only the damaged portion of the screen is
- updated.
-
-
- Note that since the shadow framebuffer is kept in main memory, all
- drawing operations are performed by the CPU and, thus, no accelerated
- hardware drawing operations are possible.
-
-
-
- AA..33.. XXiinneerraammaa
-
- Xinerama is an X extension that allows multiple physical screens
- controlled by a single X server to appear as a single screen.
- Although the extension allows clients to find the physical screen
- layout via extension requests, it is completely transparent to clients
- at the core X11 protocol level. The original public implementation of
- Xinerama came from Digital/Compaq. XFree86 rewrote it, filling in
- some missing pieces and improving both X11 core protocol compliance
- and performance. The Xinerama extension will be passing through
- X.Org's standardization process in the near future, and the sample
- implementation will be based on this rewritten version.
-
-
- The current implementation of Xinerama is based primarily in the DIX
- (device independent) and MI (machine independent) layers of the X
- server. With few exceptions the DDX layers do not need any changes to
- support Xinerama. X server extensions often do need modifications to
- provide full Xinerama functionality.
-
-
- The following is a code-level description of how Xinerama functions.
-
-
- Note: Because the Xinerama extension was originally called the
- PanoramiX extension, many of the Xinerama functions still have the
- PanoramiX prefix.
-
-
- PPaannoorraammiiXXEExxtteennssiioonnIInniitt(())
- PanoramiXExtensionInit() is a device-independent extension
- function that is called at the start of each server generation
- from InitExtensions(), which is called from the X server's
- main() function after all output devices have been initialized,
- but before any input devices have been initialized.
-
-
- PanoramiXNumScreens is set to the number of physical screens.
- If only one physical screen is present, the extension is
- disabled, and PanoramiXExtensionInit() returns without doing
- anything else.
-
-
- The Xinerama extension is registered by calling AddExtension().
-
-
- A local per-screen array of data structures (panoramiXdataPtr[])
- is allocated for each physical screen, and GC and Screen private
- indexes are allocated, and both GC and Screen private areas are
- allocated for each physical screen. These hold Xinerama-
- specific per-GC and per-Screen data. Each screen's CreateGC and
- CloseScreen functions are wrapped by XineramaCreateGC() and
- XineramaCloseScreen() respectively. Some new resource classes
- are created for Xinerama drawables and GCs, and resource types
- for Xinerama windows, pixmaps and colormaps.
-
-
- A region (XineramaScreenRegions[i]) is initialized for each
- physical screen, and single region (PanoramiXScreenRegion) is
- initialized to be the union of the screen regions. The
- panoramiXdataPtr[] array is also initialized with the size and
- origin of each screen. The relative positioning information for
- the physical screens is taken from the array dixScreenOrigins[],
- which the DDX layer must initialize in InitOutput(). The bounds
- of the combined screen is also calculated (PanoramiXPixWidth and
- PanoramiXPixHeight).
-
-
- The DIX layer has a list of function pointers (ProcVector[])
- that holds the entry points for the functions that process core
- protocol requests. The requests that Xinerama must intercept
- and break up into physical screen-specific requests are wrapped.
- The original set is copied to SavedProcVector[]. The types of
- requests intercepted are Window requests, GC requests, colormap
- requests, drawing requests, and some geometry-related requests.
- This wrapping allows the bulk of the protocol request processing
- to be handled transparently to the DIX layer. Some operations
- cannot be dealt with in this way and are handled with Xinerama-
- specific code within the DIX layer.
-
-
- PPaannoorraammiiXXCCoonnssoolliiddaattee(())
- PanoramiXConsolidate() is a device-independent extension
- function that is called directly from the X server's main()
- function after extensions and input/output devices have been
- initialized, and before the root windows are defined and
- initialized.
-
-
- This function finds the set of depths (PanoramiXDepths[]) and
- visuals (PanoramiXVisuals[]) common to all of the physical
- screens. PanoramiXNumDepths is set to the number of common
- depths, and PanoramiXNumVisuals is set to the number of common
- visuals. Resources are created for the single root window and
- the default colormap. Each of these resources has per-physical
- screen entries.
-
-
- PPaannoorraammiiXXCCrreeaatteeCCoonnnneeccttiioonnBBlloocckk(())
- PanoramiXConsolidate() is a device-independent extension
- function that is called directly from the X server's main()
- function after the per-physical screen root windows are created.
- It is called instead of the standard DIX CreateConnectionBlock()
- function. If this function returns FALSE, the X server exits
- with a fatal error. This function will return FALSE if no
- common depths were found in PanoramiXConsolidate(). With no
- common depths, Xinerama mode is not possible.
-
-
- The connection block holds the information that clients get when
- they open a connection to the X server. It includes information
- such as the supported pixmap formats, number of screens and the
- sizes, depths, visuals, default colormap information, etc, for
- each of the screens (much of information that xdpyinfo shows).
- The connection block is initialized with the combined single
- screen values that were calculated in the above two functions.
-
-
- The Xinerama extension allows the registration of connection
- block callback functions. The purpose of these is to allow
- other extensions to do processing at this point. These
- callbacks can be registered by calling
- XineramaRegisterConnectionBlockCallback() from the other
- extension's ExtensionInit() function. Each registered
- connection block callback is called at the end of
- PanoramiXCreateConnectionBlock().
-
-
- AA..33..11.. XXiinneerraammaa--ssppeecciiffiicc cchhaannggeess ttoo tthhee DDIIXX ccooddee
-
- There are a few types of Xinerama-specific changes within the DIX
- code. The main ones are described here.
-
-
- Functions that deal with colormap or GC -related operations outside of
- the intercepted protocol requests have a test added to only do the
- processing for screen numbers > 0. This is because they are handled
- for the single Xinerama screen and the processing is done once for
- screen 0.
-
-
- The handling of motion events does some coordinate translation between
- the physical screen's origin and screen zero's origin. Also, motion
- events must be reported relative to the composite screen origin rather
- than the physical screen origins.
-
-
- There is some special handling for cursor, window and event processing
- that cannot (either not at all or not conveniently) be done via the
- intercepted protocol requests. A particular case is the handling of
- pointers moving between physical screens.
-
-
- AA..33..22.. XXiinneerraammaa--ssppeecciiffiicc cchhaannggeess ttoo tthhee MMII ccooddee
-
- The only Xinerama-specific change to the MI code is in
- miSendExposures() to handle the coordinate (and window ID) translation
- for expose events.
-
-
-
- AA..33..33.. IInntteerrcceepptteedd DDIIXX ccoorree rreeqquueessttss
-
- Xinerama breaks up drawing requests for dispatch to each physical
- screen. It also breaks up windows into pieces for each physical
- screen. GCs are translated into per-screen GCs. Colormaps are
- replicated on each physical screen. The functions handling the
- intercepted requests take care of breaking the requests and
- repackaging them so that they can be passed to the standard request
- handling functions for each screen in turn. In addition, and to aid
- the repackaging, the information from many of the intercepted requests
- is used to keep up to date the necessary state information for the
- single composite screen. Requests (usually those with replies) that
- can be satisfied completely from this stored state information do not
- call the standard request handling functions.
-
-
-
- BB.. DDeevveellooppmmeenntt RReessuullttss
-
- In this section the results of each phase of development are
- discussed. This development took place between approximately June
- 2001 and July 2003.
-
-
- BB..11.. PPhhaassee II
-
- The initial development phase dealt with the basic implementation
- including the bootstrap code, which used the shadow framebuffer, and
- the unoptimized implementation, based on an Xnest-style
- implementation.
-
-
- BB..11..11.. SSccooppee
-
- The goal of Phase I is to provide fundamental functionality that can
- act as a foundation for ongoing work:
-
- 1. Develop the proxy X server
-
- +o The proxy X server will operate on the X11 protocol and relay
- requests as necessary to correctly perform the request.
-
- +o Work will be based on the existing work for Xinerama and Xnest.
-
- +o Input events and windowing operations are handled in the proxy
- server and rendering requests are repackaged and sent to each of
- the back-end servers for display.
-
- +o The multiple screen layout (including support for overlapping
- screens) will be user configurable via a configuration file or
- through the configuration tool.
-
- 2. Develop graphical configuration tool
-
- +o There will be potentially a large number of X servers to
- configure into a single display. The tool will allow the user
- to specify which servers are involved in the configuration and
- how they should be laid out.
-
- 3. Pass the X Test Suite
-
- +o The X Test Suite covers the basic X11 operations. All tests
- known to succeed must correctly operate in the distributed X
- environment.
-
-
- For this phase, the back-end X servers are assumed to be unmodified X
- servers that do not support any DMX-related protocol extensions;
- future optimization pathways are considered, but are not implemented;
- and the configuration tool is assumed to rely only on libraries in the
- X source tree (e.g., Xt).
-
-
- BB..11..22.. RReessuullttss
-
- The proxy X server, Xdmx, was developed to distribute X11 protocol
- requests to the set of back-end X servers. It opens a window on each
- back-end server, which represents the part of the front-end's root
- window that is visible on that screen. It mirrors window, pixmap and
- other state in each back-end server. Drawing requests are sent to
- either windows or pixmaps on each back-end server. This code is based
- on Xnest and uses the existing Xinerama extension.
-
-
- Input events can be taken from (1) devices attached to the back-end
- server, (2) core devices attached directly to the Xdmx server, or (3)
- from a ``console'' window on another X server. Events for these
- devices are gathered, processed and delivered to clients attached to
- the Xdmx server.
-
-
- An intuitive configuration format was developed to help the user
- easily configure the multiple back-end X servers. It was defined (see
- grammar in Xdmx man page) and a parser was implemented that is used by
- the Xdmx server and by a standalone xdmxconfig utility. The parsing
- support was implemented such that it can be easily factored out of the
- X source tree for use with other tools (e.g., vdl). Support for
- converting legacy vdl-format configuration files to the DMX format is
- provided by the vdltodmx utility.
-
-
- Originally, the configuration file was going to be a subsection of
- XFree86's XF86Config file, but that was not possible since Xdmx is a
- completely separate X server. Thus, a separate config file format was
- developed. In addition, a graphical configuration tool, xdmxconfig,
- was developed to allow the user to create and arrange the screens in
- the configuration file. The --ccoonnffiiggffiillee and --ccoonnffiigg command-line
- options can be used to start Xdmx using a configuration file.
-
-
- An extension that enables remote input testing is required for the X
- Test Suite to function. During this phase, this extension (XTEST) was
- implemented in the Xdmx server. The results from running the X Test
- Suite are described in detail below.
-
-
- BB..11..33.. XX TTeesstt SSuuiittee
-
- BB..11..33..11.. IInnttrroodduuccttiioonn
-
- The X Test Suite contains tests that verify Xlib functions operate
- correctly. The test suite is designed to run on a single X server;
- however, since X applications will not be able to tell the difference
- between the DMX server and a standard X server, the X Test Suite
- should also run on the DMX server.
-
- The Xdmx server was tested with the X Test Suite, and the existing
- failures are noted in this section. To put these results in
- perspective, we first discuss expected X Test failures and how errors
- in underlying systems can impact Xdmx test results.
-
-
- BB..11..33..22.. EExxppeecctteedd FFaaiilluurreess ffoorr aa SSiinnggllee HHeeaadd
-
- A correctly implemented X server with a single screen is expected to
- fail certain X Test tests. The following well-known errors occur
- because of rounding error in the X server code:
-
- XDrawArc: Tests 42, 63, 66, 73
- XDrawArcs: Tests 45, 66, 69, 76
-
-
-
- The following failures occur because of the high-level X server
- implementation:
-
- XLoadQueryFont: Test 1
- XListFontsWithInfo: Tests 3, 4
- XQueryFont: Tests 1, 2
-
-
-
- The following test fails when running the X server as root under Linux
- because of the way directory modes are interpreted:
-
- XWriteBitmapFile: Test 3
-
-
-
- Depending on the video card used for the back-end, other failures may
- also occur because of bugs in the low-level driver implementation.
- Over time, failures of this kind are usually fixed by XFree86, but
- will show up in Xdmx testing until then.
-
-
- BB..11..33..33.. EExxppeecctteedd FFaaiilluurreess ffoorr XXiinneerraammaa
-
- Xinerama fails several X Test Suite tests because of design decisions
- made for the current implementation of Xinerama. Over time, many of
- these errors will be corrected by XFree86 and the group working on a
- new Xinerama implementation. Therefore, Xdmx will also share X Suite
- Test failures with Xinerama.
-
- We may be able to fix or work-around some of these failures at the
- Xdmx level, but this will require additional exploration that was not
- part of Phase I.
-
- Xinerama is constantly improving, and the list of Xinerama-related
- failures depends on XFree86 version and the underlying graphics
- hardware. We tested with a variety of hardware, including nVidia, S3,
- ATI Radeon, and Matrox G400 (in dual-head mode). The list below
- includes only those failures that appear to be from the Xinerama
- layer, and does not include failures listed in the previous section,
- or failures that appear to be from the low-level graphics driver
- itself:
-
- These failures were noted with multiple Xinerama configurations:
-
- XCopyPlane: Tests 13, 22, 31 (well-known Xinerama implementation issue)
- XSetFontPath: Test 4
- XGetDefault: Test 5
- XMatchVisualInfo: Test 1
-
-
-
- These failures were noted only when using one dual-head video card
- with a 4.2.99.x XFree86 server:
-
- XListPixmapFormats: Test 1
- XDrawRectangles: Test 45
-
-
-
- These failures were noted only when using two video cards from
- different vendors with a 4.1.99.x XFree86 server:
-
- XChangeWindowAttributes: Test 32
- XCreateWindow: Test 30
- XDrawLine: Test 22
- XFillArc: Test 22
- XChangeKeyboardControl: Tests 9, 10
- XRebindKeysym: Test 1
-
-
-
- BB..11..33..44.. AAddddiittiioonnaall FFaaiilluurreess ffrroomm XXddmmxx
-
- When running Xdmx, no unexpected failures were noted. Since the Xdmx
- server is based on Xinerama, we expect to have most of the Xinerama
- failures present in the Xdmx server. Similarly, since the Xdmx server
- must rely on the low-level device drivers on each back-end server, we
- also expect that Xdmx will exhibit most of the back-end failures.
- Here is a summary:
-
- XListPixmapFormats: Test 1 (configuration dependent)
- XChangeWindowAttributes: Test 32
- XCreateWindow: Test 30
- XCopyPlane: Test 13, 22, 31
- XSetFontPath: Test 4
- XGetDefault: Test 5 (configuration dependent)
- XMatchVisualInfo: Test 1
- XRebindKeysym: Test 1 (configuration dependent)
-
-
-
- Note that this list is shorter than the combined list for Xinerama
- because Xdmx uses different code paths to perform some Xinerama
- operations. Further, some Xinerama failures have been fixed in the
- XFree86 4.2.99.x CVS repository.
-
-
- BB..11..33..55.. SSuummmmaarryy aanndd FFuuttuurree WWoorrkk
-
- Running the X Test Suite on Xdmx does not produce any failures that
- cannot be accounted for by the underlying Xinerama subsystem used by
- the front-end or by the low-level device-driver code running on the
- back-end X servers. The Xdmx server therefore is as ``correct'' as
- possible with respect to the standard set of X Test Suite tests.
-
- During the following phases, we will continue to verify Xdmx
- correctness using the X Test Suite. We may also use other tests
- suites or write additional tests that run under the X Test Suite that
- specifically verify the expected behavior of DMX.
-
-
-
- BB..11..44.. FFoonnttss
-
- In Phase I, fonts are handled directly by both the front-end and the
- back-end servers, which is required since we must treat each back-end
- server during this phase as a ``black box''. What this requires is
- that tthhee ffrroonntt-- aanndd bbaacckk--eenndd sseerrvveerrss mmuusstt sshhaarree tthhee eexxaacctt ssaammee ffoonntt
- ppaatthh. There are two ways to help make sure that all servers share the
- same font path:
-
-
- 1. First, each server can be configured to use the same font server.
- The font server, xfs, can be configured to serve fonts to multiple
- X servers via TCP.
-
- 2. Second, each server can be configured to use the same font path and
- either those font paths can be copied to each back-end machine or
- they can be mounted (e.g., via NFS) on each back-end machine.
-
-
- One additional concern is that a client program can set its own font
- path, and if it does so, then that font path must be available on each
- back-end machine.
-
-
- The -fontpath command line option was added to allow users to
- initialize the font path of the front end server. This font path is
- propagated to each back-end server when the default font is loaded.
- If there are any problems, an error message is printed, which will
- describe the problem and list the current font path. For more
- information about setting the font path, see the -fontpath option
- description in the man page.
-
-
- BB..11..55.. PPeerrffoorrmmaannccee
-
- Phase I of development was not intended to optimize performance. Its
- focus was on completely and correctly handling the base X11 protocol
- in the Xdmx server. However, several insights were gained during
- Phase I, which are listed here for reference during the next phase of
- development.
-
-
- 1. Calls to XSync() can slow down rendering since it requires a
- complete round trip to and from a back-end server. This is
- especially problematic when communicating over long haul networks.
-
- 2. Sending drawing requests to only the screens that they overlap
- should improve performance.
-
-
- BB..11..66.. PPiixxmmaappss
-
- Pixmaps were originally expected to be handled entirely in the front-
- end X server; however, it was found that this overly complicated the
- rendering code and would have required sending potentially large
- images to each back server that required them when copying from pixmap
- to screen. Thus, pixmap state is mirrored in the back-end server just
- as it is with regular window state. With this implementation, the
- same rendering code that draws to windows can be used to draw to
- pixmaps on the back-end server, and no large image transfers are
- required to copy from pixmap to window.
-
-
-
- BB..22.. PPhhaassee IIII
-
- The second phase of development concentrates on performance
- optimizations. These optimizations are documented here, with x11perf
- data to show how the optimizations improve performance.
-
-
- All benchmarks were performed by running Xdmx on a dual processor
- 1.4GHz AMD Athlon machine with 1GB of RAM connecting over 100baseT to
- two single-processor 1GHz Pentium III machines with 256MB of RAM and
- ATI Rage 128 (RF) video cards. The front end was running Linux
- 2.4.20-pre1-ac1 and the back ends were running Linux 2.4.7-10 and
- version 4.2.99.1 of XFree86 pulled from the XFree86 CVS repository on
- August 7, 2002. All systems were running Red Hat Linux 7.2.
-
-
- BB..22..11.. MMoovviinngg ffrroomm XXFFrreeee8866 44..11..9999..11 ttoo 44..22..00..00
-
- For phase II, the working source tree was moved to the branch tagged
- with dmx-1-0-branch and was updated from version 4.1.99.1 (20 August
- 2001) of the XFree86 sources to version 4.2.0.0 (18 January 2002).
- After this update, the following tests were noted to be more than 10%
- faster:
-
- 1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple)
- 1.16 Fill 1x1 tiled trapezoid (161x145 tile)
- 1.13 Fill 10x10 tiled trapezoid (161x145 tile)
- 1.17 Fill 100x100 tiled trapezoid (161x145 tile)
- 1.16 Fill 1x1 tiled trapezoid (216x208 tile)
- 1.20 Fill 10x10 tiled trapezoid (216x208 tile)
- 1.15 Fill 100x100 tiled trapezoid (216x208 tile)
- 1.37 Circulate Unmapped window (200 kids)
-
-
-
- And the following tests were noted to be more than 10% slower:
-
- 0.88 Unmap window via parent (25 kids)
- 0.75 Circulate Unmapped window (4 kids)
- 0.79 Circulate Unmapped window (16 kids)
- 0.80 Circulate Unmapped window (25 kids)
- 0.82 Circulate Unmapped window (50 kids)
- 0.85 Circulate Unmapped window (75 kids)
-
-
-
- These changes were not caused by any changes in the DMX system, and
- may point to changes in the XFree86 tree or to tests that have more
- "jitter" than most other x11perf tests.
-
-
- BB..22..22.. GGlloobbaall cchhaannggeess
-
- During the development of the Phase II DMX server, several global
- changes were made. These changes were also compared with the Phase I
- server. The following tests were noted to be more than 10% faster:
-
-
-
- 1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple)
- 1.15 Fill 1x1 tiled trapezoid (161x145 tile)
- 1.13 Fill 10x10 tiled trapezoid (161x145 tile)
- 1.17 Fill 100x100 tiled trapezoid (161x145 tile)
- 1.16 Fill 1x1 tiled trapezoid (216x208 tile)
- 1.19 Fill 10x10 tiled trapezoid (216x208 tile)
- 1.15 Fill 100x100 tiled trapezoid (216x208 tile)
- 1.15 Circulate Unmapped window (4 kids)
-
-
-
- The following tests were noted to be more than 10% slower:
-
- 0.69 Scroll 10x10 pixels
- 0.68 Scroll 100x100 pixels
- 0.68 Copy 10x10 from window to window
- 0.68 Copy 100x100 from window to window
- 0.76 Circulate Unmapped window (75 kids)
- 0.83 Circulate Unmapped window (100 kids)
-
-
-
- For the remainder of this analysis, the baseline of comparison will be
- the Phase II deliverable with all optimizations disabled (unless
- otherwise noted). This will highlight how the optimizations in
- isolation impact performance.
-
-
- BB..22..33.. XXSSyynncc(()) BBaattcchhiinngg
-
- During the Phase I implementation, XSync() was called after every
- protocol request made by the DMX server. This provided the DMX server
- with an interactive feel, but defeated X11's protocol buffering system
- and introduced round-trip wire latency into every operation. During
- Phase II, DMX was changed so that protocol requests are no longer
- followed by calls to XSync(). Instead, the need for an XSync() is
- noted, and XSync() calls are only made every 100mS or when the DMX
- server specifically needs to make a call to guarantee interactivity.
- With this new system, X11 buffers protocol as much as possible during
- a 100mS interval, and many unnecessary XSync() calls are avoided.
-
-
- Out of more than 300 x11perf tests, 8 tests became more than 100 times
- faster, with 68 more than 50X faster, 114 more than 10X faster, and
- 181 more than 2X faster. See table below for summary.
-
-
- The following tests were noted to be more than 10% slower with XSync()
- batching on:
-
- 0.88 500x500 tiled rectangle (161x145 tile)
- 0.89 Copy 500x500 from window to window
-
-
-
- BB..22..44.. OOffffssccrreeeenn OOppttiimmiizzaattiioonn
-
- Windows span one or more of the back-end servers' screens; however,
- during Phase I development, windows were created on every back-end
- server and every rendering request was sent to every window regardless
- of whether or not that window was visible. With the offscreen
- optimization, the DMX server tracks when a window is completely off of
- a back-end server's screen and, in that case, it does not send
- rendering requests to those back-end windows. This optimization saves
- bandwidth between the front and back-end servers, and it reduces the
- number of XSync() calls. The performance tests were run on a DMX
- system with only two back-end servers. Greater performance gains will
- be had as the number of back-end servers increases.
-
-
- Out of more than 300 x11perf tests, 3 tests were at least twice as
- fast, and 146 tests were at least 10% faster. Two tests were more
- than 10% slower with the offscreen optimization:
-
- 0.88 Hide/expose window via popup (4 kids)
- 0.89 Resize unmapped window (75 kids)
-
-
-
- BB..22..55.. LLaazzyy WWiinnddooww CCrreeaattiioonn OOppttiimmiizzaattiioonn
-
- As mentioned above, during Phase I, windows were created on every
- back-end server even if they were not visible on that back-end. With
- the lazy window creation optimization, the DMX server does not create
- windows on a back-end server until they are either visible or they
- become the parents of a visible window. This optimization builds on
- the offscreen optimization (described above) and requires it to be
- enabled.
-
-
- The lazy window creation optimization works by creating the window
- data structures in the front-end server when a client creates a
- window, but delays creation of the window on the back-end server(s).
- A private window structure in the DMX server saves the relevant window
- data and tracks changes to the window's attributes and stacking order
- for later use. The only times a window is created on a back-end
- server are (1) when it is mapped and is at least partially overlapping
- the back-end server's screen (tracked by the offscreen optimization),
- or (2) when the window becomes the parent of a previously visible
- window. The first case occurs when a window is mapped or when a
- visible window is copied, moved or resized and now overlaps the back-
- end server's screen. The second case occurs when starting a window
- manager after having created windows to which the window manager needs
- to add decorations.
-
-
- When either case occurs, a window on the back-end server is created
- using the data saved in the DMX server's window private data
- structure. The stacking order is then adjusted to correctly place the
- window on the back-end and lastly the window is mapped. From this
- time forward, the window is handled exactly as if the window had been
- created at the time of the client's request.
-
-
- Note that when a window is no longer visible on a back-end server's
- screen (e.g., it is moved offscreen), the window is not destroyed;
- rather, it is kept and reused later if the window once again becomes
- visible on the back-end server's screen. Originally with this
- optimization, destroying windows was implemented but was later
- rejected because it increased bandwidth when windows were opaquely
- moved or resized, which is common in many window managers.
-
-
-
- The performance tests were run on a DMX system with only two back-end
- servers. Greater performance gains will be had as the number of back-
- end servers increases.
-
-
- This optimization improved the following x11perf tests by more than
- 10%:
-
- 1.10 500x500 rectangle outline
- 1.12 Fill 100x100 stippled trapezoid (161x145 stipple)
- 1.20 Circulate Unmapped window (50 kids)
- 1.19 Circulate Unmapped window (75 kids)
-
-
-
- BB..22..66.. SSuubbddiivviiddiinngg RReennddeerriinngg PPrriimmiittiivveess
-
- X11 imaging requests transfer significant data between the client and
- the X server. During Phase I, the DMX server would then transfer the
- image data to each back-end server. Even with the offscreen
- optimization (above), these requests still required transferring
- significant data to each back-end server that contained a visible
- portion of the window. For example, if the client uses XPutImage() to
- copy an image to a window that overlaps the entire DMX screen, then
- the entire image is copied by the DMX server to every back-end server.
-
-
- To reduce the amount of data transferred between the DMX server and
- the back-end servers when XPutImage() is called, the image data is
- subdivided and only the data that will be visible on a back-end
- server's screen is sent to that back-end server. Xinerama already
- implements a subdivision algorithm for XGetImage() and no further
- optimization was needed.
-
-
- Other rendering primitives were analyzed, but the time required to
- subdivide these primitives was a significant proportion of the time
- required to send the entire rendering request to the back-end server,
- so this optimization was rejected for the other rendering primitives.
-
-
- Again, the performance tests were run on a DMX system with only two
- back-end servers. Greater performance gains will be had as the number
- of back-end servers increases.
-
-
- This optimization improved the following x11perf tests by more than
- 10%:
-
- 1.12 Fill 100x100 stippled trapezoid (161x145 stipple)
- 1.26 PutImage 10x10 square
- 1.83 PutImage 100x100 square
- 1.91 PutImage 500x500 square
- 1.40 PutImage XY 10x10 square
- 1.48 PutImage XY 100x100 square
- 1.50 PutImage XY 500x500 square
- 1.45 Circulate Unmapped window (75 kids)
- 1.74 Circulate Unmapped window (100 kids)
-
-
-
- The following test was noted to be more than 10% slower with this
- optimization:
-
- 0.88 10-pixel fill chord partial circle
-
-
-
- BB..22..77.. SSuummmmaarryy ooff xx1111ppeerrff DDaattaa
-
- With all of the optimizations on, 53 x11perf tests are more than 100X
- faster than the unoptimized Phase II deliverable, with 69 more than
- 50X faster, 73 more than 10X faster, and 199 more than twice as fast.
- No tests were more than 10% slower than the unoptimized Phase II
- deliverable. (Compared with the Phase I deliverable, only Circulate
- Unmapped window (100 kids) was more than 10% slower than the Phase II
- deliverable. As noted above, this test seems to have wider
- variability than other x11perf tests.)
-
-
- The following table summarizes relative x11perf test changes for all
- optimizations individually and collectively. Note that some of the
- optimizations have a synergistic effect when used together.
-
-
-
- 1: XSync() batching only
- 2: Off screen optimizations only
- 3: Window optimizations only
- 4: Subdivprims only
- 5: All optimizations
-
- 1 2 3 4 5 Operation
- ------ ---- ---- ---- ------ ---------
- 2.14 1.85 1.00 1.00 4.13 Dot
- 1.67 1.80 1.00 1.00 3.31 1x1 rectangle
- 2.38 1.43 1.00 1.00 2.44 10x10 rectangle
- 1.00 1.00 0.92 0.98 1.00 100x100 rectangle
- 1.00 1.00 1.00 1.00 1.00 500x500 rectangle
- 1.83 1.85 1.05 1.06 3.54 1x1 stippled rectangle (8x8 stipple)
- 2.43 1.43 1.00 1.00 2.41 10x10 stippled rectangle (8x8 stipple)
- 0.98 1.00 1.00 1.00 1.00 100x100 stippled rectangle (8x8 stipple)
- 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (8x8 stipple)
- 1.75 1.75 1.00 1.00 3.40 1x1 opaque stippled rectangle (8x8 stipple)
- 2.38 1.42 1.00 1.00 2.34 10x10 opaque stippled rectangle (8x8 stipple)
- 1.00 1.00 0.97 0.97 1.00 100x100 opaque stippled rectangle (8x8 stipple)
- 1.00 1.00 1.00 1.00 0.99 500x500 opaque stippled rectangle (8x8 stipple)
- 1.82 1.82 1.04 1.04 3.56 1x1 tiled rectangle (4x4 tile)
- 2.33 1.42 1.00 1.00 2.37 10x10 tiled rectangle (4x4 tile)
- 1.00 0.92 1.00 1.00 1.00 100x100 tiled rectangle (4x4 tile)
- 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (4x4 tile)
- 1.94 1.62 1.00 1.00 3.66 1x1 stippled rectangle (17x15 stipple)
- 1.74 1.28 1.00 1.00 1.73 10x10 stippled rectangle (17x15 stipple)
- 1.00 1.00 1.00 0.89 0.98 100x100 stippled rectangle (17x15 stipple)
- 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (17x15 stipple)
- 1.94 1.62 1.00 1.00 3.67 1x1 opaque stippled rectangle (17x15 stipple)
- 1.69 1.26 1.00 1.00 1.66 10x10 opaque stippled rectangle (17x15 stipple)
- 1.00 0.95 1.00 1.00 1.00 100x100 opaque stippled rectangle (17x15 stipple)
- 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (17x15 stipple)
- 1.93 1.61 0.99 0.99 3.69 1x1 tiled rectangle (17x15 tile)
- 1.73 1.27 1.00 1.00 1.72 10x10 tiled rectangle (17x15 tile)
- 1.00 1.00 1.00 1.00 0.98 100x100 tiled rectangle (17x15 tile)
- 1.00 1.00 0.97 0.97 1.00 500x500 tiled rectangle (17x15 tile)
- 1.95 1.63 1.00 1.00 3.83 1x1 stippled rectangle (161x145 stipple)
- 1.80 1.30 1.00 1.00 1.83 10x10 stippled rectangle (161x145 stipple)
- 0.97 1.00 1.00 1.00 1.01 100x100 stippled rectangle (161x145 stipple)
- 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (161x145 stipple)
- 1.95 1.63 1.00 1.00 3.56 1x1 opaque stippled rectangle (161x145 stipple)
- 1.65 1.25 1.00 1.00 1.68 10x10 opaque stippled rectangle (161x145 stipple)
- 1.00 1.00 1.00 1.00 1.01 100x100 opaque stippled rectangle (161x145...
- 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (161x145...
- 1.95 1.63 0.98 0.99 3.80 1x1 tiled rectangle (161x145 tile)
- 1.67 1.26 1.00 1.00 1.67 10x10 tiled rectangle (161x145 tile)
- 1.13 1.14 1.14 1.14 1.14 100x100 tiled rectangle (161x145 tile)
- 0.88 1.00 1.00 1.00 0.99 500x500 tiled rectangle (161x145 tile)
- 1.93 1.63 1.00 1.00 3.53 1x1 tiled rectangle (216x208 tile)
- 1.69 1.26 1.00 1.00 1.66 10x10 tiled rectangle (216x208 tile)
- 1.00 1.00 1.00 1.00 1.00 100x100 tiled rectangle (216x208 tile)
- 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (216x208 tile)
- 1.82 1.70 1.00 1.00 3.38 1-pixel line segment
- 2.07 1.56 0.90 1.00 3.31 10-pixel line segment
- 1.29 1.10 1.00 1.00 1.27 100-pixel line segment
- 1.05 1.06 1.03 1.03 1.09 500-pixel line segment
- 1.30 1.13 1.00 1.00 1.29 100-pixel line segment (1 kid)
- 1.32 1.15 1.00 1.00 1.32 100-pixel line segment (2 kids)
- 1.33 1.16 1.00 1.00 1.33 100-pixel line segment (3 kids)
- 1.92 1.64 1.00 1.00 3.73 10-pixel dashed segment
- 1.34 1.16 1.00 1.00 1.34 100-pixel dashed segment
- 1.24 1.11 0.99 0.97 1.23 100-pixel double-dashed segment
- 1.72 1.77 1.00 1.00 3.25 10-pixel horizontal line segment
- 1.83 1.66 1.01 1.00 3.54 100-pixel horizontal line segment
- 1.86 1.30 1.00 1.00 1.84 500-pixel horizontal line segment
- 2.11 1.52 1.00 0.99 3.02 10-pixel vertical line segment
- 1.21 1.10 1.00 1.00 1.20 100-pixel vertical line segment
- 1.03 1.03 1.00 1.00 1.02 500-pixel vertical line segment
- 4.42 1.68 1.00 1.01 4.64 10x1 wide horizontal line segment
- 1.83 1.31 1.00 1.00 1.83 100x10 wide horizontal line segment
- 1.07 1.00 0.96 1.00 1.07 500x50 wide horizontal line segment
- 4.10 1.67 1.00 1.00 4.62 10x1 wide vertical line segment
- 1.50 1.24 1.06 1.06 1.48 100x10 wide vertical line segment
- 1.06 1.03 1.00 1.00 1.05 500x50 wide vertical line segment
- 2.54 1.61 1.00 1.00 3.61 1-pixel line
- 2.71 1.48 1.00 1.00 2.67 10-pixel line
- 1.19 1.09 1.00 1.00 1.19 100-pixel line
- 1.04 1.02 1.00 1.00 1.03 500-pixel line
- 2.68 1.51 0.98 1.00 3.17 10-pixel dashed line
- 1.23 1.11 0.99 0.99 1.23 100-pixel dashed line
- 1.15 1.08 1.00 1.00 1.15 100-pixel double-dashed line
- 2.27 1.39 1.00 1.00 2.23 10x1 wide line
- 1.20 1.09 1.00 1.00 1.20 100x10 wide line
- 1.04 1.02 1.00 1.00 1.04 500x50 wide line
- 1.52 1.45 1.00 1.00 1.52 100x10 wide dashed line
- 1.54 1.47 1.00 1.00 1.54 100x10 wide double-dashed line
- 1.97 1.30 0.96 0.95 1.95 10x10 rectangle outline
- 1.44 1.27 1.00 1.00 1.43 100x100 rectangle outline
- 3.22 2.16 1.10 1.09 3.61 500x500 rectangle outline
- 1.95 1.34 1.00 1.00 1.90 10x10 wide rectangle outline
- 1.14 1.14 1.00 1.00 1.13 100x100 wide rectangle outline
- 1.00 1.00 1.00 1.00 1.00 500x500 wide rectangle outline
- 1.57 1.72 1.00 1.00 3.03 1-pixel circle
- 1.96 1.35 1.00 1.00 1.92 10-pixel circle
- 1.21 1.07 0.86 0.97 1.20 100-pixel circle
- 1.08 1.04 1.00 1.00 1.08 500-pixel circle
- 1.39 1.19 1.03 1.03 1.38 100-pixel dashed circle
- 1.21 1.11 1.00 1.00 1.23 100-pixel double-dashed circle
- 1.59 1.28 1.00 1.00 1.58 10-pixel wide circle
- 1.22 1.12 0.99 1.00 1.22 100-pixel wide circle
- 1.06 1.04 1.00 1.00 1.05 500-pixel wide circle
- 1.87 1.84 1.00 1.00 1.85 100-pixel wide dashed circle
- 1.90 1.93 1.01 1.01 1.90 100-pixel wide double-dashed circle
- 2.13 1.43 1.00 1.00 2.32 10-pixel partial circle
- 1.42 1.18 1.00 1.00 1.42 100-pixel partial circle
- 1.92 1.85 1.01 1.01 1.89 10-pixel wide partial circle
- 1.73 1.67 1.00 1.00 1.73 100-pixel wide partial circle
- 1.36 1.95 1.00 1.00 2.64 1-pixel solid circle
- 2.02 1.37 1.00 1.00 2.03 10-pixel solid circle
- 1.19 1.09 1.00 1.00 1.19 100-pixel solid circle
- 1.02 0.99 1.00 1.00 1.01 500-pixel solid circle
- 1.74 1.28 1.00 0.88 1.73 10-pixel fill chord partial circle
- 1.31 1.13 1.00 1.00 1.31 100-pixel fill chord partial circle
- 1.67 1.31 1.03 1.03 1.72 10-pixel fill slice partial circle
- 1.30 1.13 1.00 1.00 1.28 100-pixel fill slice partial circle
- 2.45 1.49 1.01 1.00 2.71 10-pixel ellipse
- 1.22 1.10 1.00 1.00 1.22 100-pixel ellipse
- 1.09 1.04 1.00 1.00 1.09 500-pixel ellipse
- 1.90 1.28 1.00 1.00 1.89 100-pixel dashed ellipse
- 1.62 1.24 0.96 0.97 1.61 100-pixel double-dashed ellipse
- 2.43 1.50 1.00 1.00 2.42 10-pixel wide ellipse
- 1.61 1.28 1.03 1.03 1.60 100-pixel wide ellipse
- 1.08 1.05 1.00 1.00 1.08 500-pixel wide ellipse
- 1.93 1.88 1.00 1.00 1.88 100-pixel wide dashed ellipse
- 1.94 1.89 1.01 1.00 1.94 100-pixel wide double-dashed ellipse
- 2.31 1.48 1.00 1.00 2.67 10-pixel partial ellipse
- 1.38 1.17 1.00 1.00 1.38 100-pixel partial ellipse
- 2.00 1.85 0.98 0.97 1.98 10-pixel wide partial ellipse
- 1.89 1.86 1.00 1.00 1.89 100-pixel wide partial ellipse
- 3.49 1.60 1.00 1.00 3.65 10-pixel filled ellipse
- 1.67 1.26 1.00 1.00 1.67 100-pixel filled ellipse
- 1.06 1.04 1.00 1.00 1.06 500-pixel filled ellipse
- 2.38 1.43 1.01 1.00 2.32 10-pixel fill chord partial ellipse
- 2.06 1.30 1.00 1.00 2.05 100-pixel fill chord partial ellipse
- 2.27 1.41 1.00 1.00 2.27 10-pixel fill slice partial ellipse
- 1.98 1.33 1.00 0.97 1.97 100-pixel fill slice partial ellipse
- 57.46 1.99 1.01 1.00 114.92 Fill 1x1 equivalent triangle
- 56.94 1.98 1.01 1.00 73.89 Fill 10x10 equivalent triangle
- 6.07 1.75 1.00 1.00 6.07 Fill 100x100 equivalent triangle
- 51.12 1.98 1.00 1.00 102.81 Fill 1x1 trapezoid
- 51.42 1.82 1.01 1.00 94.89 Fill 10x10 trapezoid
- 6.47 1.80 1.00 1.00 6.44 Fill 100x100 trapezoid
- 1.56 1.28 1.00 0.99 1.56 Fill 300x300 trapezoid
- 51.27 1.97 0.96 0.97 102.54 Fill 1x1 stippled trapezoid (8x8 stipple)
- 51.73 2.00 1.02 1.02 67.92 Fill 10x10 stippled trapezoid (8x8 stipple)
- 5.36 1.72 1.00 1.00 5.36 Fill 100x100 stippled trapezoid (8x8 stipple)
- 1.54 1.26 1.00 1.00 1.59 Fill 300x300 stippled trapezoid (8x8 stipple)
- 51.41 1.94 1.01 1.00 102.82 Fill 1x1 opaque stippled trapezoid (8x8 stipple)
- 50.71 1.95 0.99 1.00 65.44 Fill 10x10 opaque stippled trapezoid (8x8...
- 5.33 1.73 1.00 1.00 5.36 Fill 100x100 opaque stippled trapezoid (8x8...
- 1.58 1.25 1.00 1.00 1.58 Fill 300x300 opaque stippled trapezoid (8x8...
- 51.56 1.96 0.99 0.90 103.68 Fill 1x1 tiled trapezoid (4x4 tile)
- 51.59 1.99 1.01 1.01 62.25 Fill 10x10 tiled trapezoid (4x4 tile)
- 5.38 1.72 1.00 1.00 5.38 Fill 100x100 tiled trapezoid (4x4 tile)
- 1.54 1.25 1.00 0.99 1.58 Fill 300x300 tiled trapezoid (4x4 tile)
- 51.70 1.98 1.01 1.01 103.98 Fill 1x1 stippled trapezoid (17x15 stipple)
- 44.86 1.97 1.00 1.00 44.86 Fill 10x10 stippled trapezoid (17x15 stipple)
- 2.74 1.56 1.00 1.00 2.73 Fill 100x100 stippled trapezoid (17x15 stipple)
- 1.29 1.14 1.00 1.00 1.27 Fill 300x300 stippled trapezoid (17x15 stipple)
- 51.41 1.96 0.96 0.95 103.39 Fill 1x1 opaque stippled trapezoid (17x15...
- 45.14 1.96 1.01 1.00 45.14 Fill 10x10 opaque stippled trapezoid (17x15...
- 2.68 1.56 1.00 1.00 2.68 Fill 100x100 opaque stippled trapezoid (17x15...
- 1.26 1.10 1.00 1.00 1.28 Fill 300x300 opaque stippled trapezoid (17x15...
- 51.13 1.97 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (17x15 tile)
- 47.58 1.96 1.00 1.00 47.86 Fill 10x10 tiled trapezoid (17x15 tile)
- 2.74 1.56 1.00 1.00 2.74 Fill 100x100 tiled trapezoid (17x15 tile)
- 1.29 1.14 1.00 1.00 1.28 Fill 300x300 tiled trapezoid (17x15 tile)
- 51.13 1.97 0.99 0.97 103.39 Fill 1x1 stippled trapezoid (161x145 stipple)
- 45.14 1.97 1.00 1.00 44.29 Fill 10x10 stippled trapezoid (161x145 stipple)
- 3.02 1.77 1.12 1.12 3.38 Fill 100x100 stippled trapezoid (161x145 stipple)
- 1.31 1.13 1.00 1.00 1.30 Fill 300x300 stippled trapezoid (161x145 stipple)
- 51.27 1.97 1.00 1.00 103.10 Fill 1x1 opaque stippled trapezoid (161x145...
- 45.01 1.97 1.00 1.00 45.01 Fill 10x10 opaque stippled trapezoid (161x145...
- 2.67 1.56 1.00 1.00 2.69 Fill 100x100 opaque stippled trapezoid (161x145..
- 1.29 1.13 1.00 1.01 1.27 Fill 300x300 opaque stippled trapezoid (161x145..
- 51.41 1.96 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (161x145 tile)
- 45.01 1.96 0.98 1.00 45.01 Fill 10x10 tiled trapezoid (161x145 tile)
- 2.62 1.36 1.00 1.00 2.69 Fill 100x100 tiled trapezoid (161x145 tile)
- 1.27 1.13 1.00 1.00 1.22 Fill 300x300 tiled trapezoid (161x145 tile)
- 51.13 1.98 1.00 1.00 103.39 Fill 1x1 tiled trapezoid (216x208 tile)
- 45.14 1.97 1.01 0.99 45.14 Fill 10x10 tiled trapezoid (216x208 tile)
- 2.62 1.55 1.00 1.00 2.71 Fill 100x100 tiled trapezoid (216x208 tile)
- 1.28 1.13 1.00 1.00 1.20 Fill 300x300 tiled trapezoid (216x208 tile)
- 50.71 1.95 1.00 1.00 54.70 Fill 10x10 equivalent complex polygon
- 5.51 1.71 0.96 0.98 5.47 Fill 100x100 equivalent complex polygons
- 8.39 1.97 1.00 1.00 16.75 Fill 10x10 64-gon (Convex)
- 8.38 1.83 1.00 1.00 8.43 Fill 100x100 64-gon (Convex)
- 8.50 1.96 1.00 1.00 16.64 Fill 10x10 64-gon (Complex)
- 8.26 1.83 1.00 1.00 8.35 Fill 100x100 64-gon (Complex)
- 14.09 1.87 1.00 1.00 14.05 Char in 80-char line (6x13)
- 11.91 1.87 1.00 1.00 11.95 Char in 70-char line (8x13)
- 11.16 1.85 1.01 1.00 11.10 Char in 60-char line (9x15)
- 10.09 1.78 1.00 1.00 10.09 Char16 in 40-char line (k14)
- 6.15 1.75 1.00 1.00 6.31 Char16 in 23-char line (k24)
- 11.92 1.90 1.03 1.03 11.88 Char in 80-char line (TR 10)
- 8.18 1.78 1.00 0.99 8.17 Char in 30-char line (TR 24)
- 42.83 1.44 1.01 1.00 42.11 Char in 20/40/20 line (6x13, TR 10)
- 27.45 1.43 1.01 1.01 27.45 Char16 in 7/14/7 line (k14, k24)
- 12.13 1.85 1.00 1.00 12.05 Char in 80-char image line (6x13)
- 10.00 1.84 1.00 1.00 10.00 Char in 70-char image line (8x13)
- 9.18 1.83 1.00 1.00 9.12 Char in 60-char image line (9x15)
- 9.66 1.82 0.98 0.95 9.66 Char16 in 40-char image line (k14)
- 5.82 1.72 1.00 1.00 5.99 Char16 in 23-char image line (k24)
- 8.70 1.80 1.00 1.00 8.65 Char in 80-char image line (TR 10)
- 4.67 1.66 1.00 1.00 4.67 Char in 30-char image line (TR 24)
- 84.43 1.47 1.00 1.00 124.18 Scroll 10x10 pixels
- 3.73 1.50 1.00 0.98 3.73 Scroll 100x100 pixels
- 1.00 1.00 1.00 1.00 1.00 Scroll 500x500 pixels
- 84.43 1.51 1.00 1.00 134.02 Copy 10x10 from window to window
- 3.62 1.51 0.98 0.98 3.62 Copy 100x100 from window to window
- 0.89 1.00 1.00 1.00 1.00 Copy 500x500 from window to window
- 57.06 1.99 1.00 1.00 88.64 Copy 10x10 from pixmap to window
- 2.49 2.00 1.00 1.00 2.48 Copy 100x100 from pixmap to window
- 1.00 0.91 1.00 1.00 0.98 Copy 500x500 from pixmap to window
- 2.04 1.01 1.00 1.00 2.03 Copy 10x10 from window to pixmap
- 1.05 1.00 1.00 1.00 1.05 Copy 100x100 from window to pixmap
- 1.00 1.00 0.93 1.00 1.04 Copy 500x500 from window to pixmap
- 58.52 1.03 1.03 1.02 57.95 Copy 10x10 from pixmap to pixmap
- 2.40 1.00 1.00 1.00 2.45 Copy 100x100 from pixmap to pixmap
- 1.00 1.00 1.00 1.00 1.00 Copy 500x500 from pixmap to pixmap
- 51.57 1.92 1.00 1.00 85.75 Copy 10x10 1-bit deep plane
- 6.37 1.75 1.01 1.01 6.37 Copy 100x100 1-bit deep plane
- 1.26 1.11 1.00 1.00 1.24 Copy 500x500 1-bit deep plane
- 4.23 1.63 0.98 0.97 4.38 Copy 10x10 n-bit deep plane
- 1.04 1.02 1.00 1.00 1.04 Copy 100x100 n-bit deep plane
- 1.00 1.00 1.00 1.00 1.00 Copy 500x500 n-bit deep plane
- 6.45 1.98 1.00 1.26 12.80 PutImage 10x10 square
- 1.10 1.87 1.00 1.83 2.11 PutImage 100x100 square
- 1.02 1.93 1.00 1.91 1.91 PutImage 500x500 square
- 4.17 1.78 1.00 1.40 7.18 PutImage XY 10x10 square
- 1.27 1.49 0.97 1.48 2.10 PutImage XY 100x100 square
- 1.00 1.50 1.00 1.50 1.52 PutImage XY 500x500 square
- 1.07 1.01 1.00 1.00 1.06 GetImage 10x10 square
- 1.01 1.00 1.00 1.00 1.01 GetImage 100x100 square
- 1.00 1.00 1.00 1.00 1.00 GetImage 500x500 square
- 1.56 1.00 0.99 0.97 1.56 GetImage XY 10x10 square
- 1.02 1.00 1.00 1.00 1.02 GetImage XY 100x100 square
- 1.00 1.00 1.00 1.00 1.00 GetImage XY 500x500 square
- 1.00 1.00 1.01 0.98 0.95 X protocol NoOperation
- 1.02 1.03 1.04 1.03 1.00 QueryPointer
- 1.03 1.02 1.04 1.03 1.00 GetProperty
- 100.41 1.51 1.00 1.00 198.76 Change graphics context
- 45.81 1.00 0.99 0.97 57.10 Create and map subwindows (4 kids)
- 78.45 1.01 1.02 1.02 63.07 Create and map subwindows (16 kids)
- 73.91 1.01 1.00 1.00 56.37 Create and map subwindows (25 kids)
- 73.22 1.00 1.00 1.00 49.07 Create and map subwindows (50 kids)
- 72.36 1.01 0.99 1.00 32.14 Create and map subwindows (75 kids)
- 70.34 1.00 1.00 1.00 30.12 Create and map subwindows (100 kids)
- 55.00 1.00 1.00 0.99 23.75 Create and map subwindows (200 kids)
- 55.30 1.01 1.00 1.00 141.03 Create unmapped window (4 kids)
- 55.38 1.01 1.01 1.00 163.25 Create unmapped window (16 kids)
- 54.75 0.96 1.00 0.99 166.95 Create unmapped window (25 kids)
- 54.83 1.00 1.00 0.99 178.81 Create unmapped window (50 kids)
- 55.38 1.01 1.01 1.00 181.20 Create unmapped window (75 kids)
- 55.38 1.01 1.01 1.00 181.20 Create unmapped window (100 kids)
- 54.87 1.01 1.01 1.00 182.05 Create unmapped window (200 kids)
- 28.13 1.00 1.00 1.00 30.75 Map window via parent (4 kids)
- 36.14 1.01 1.01 1.01 32.58 Map window via parent (16 kids)
- 26.13 1.00 0.98 0.95 29.85 Map window via parent (25 kids)
- 40.07 1.00 1.01 1.00 27.57 Map window via parent (50 kids)
- 23.26 0.99 1.00 1.00 18.23 Map window via parent (75 kids)
- 22.91 0.99 1.00 0.99 16.52 Map window via parent (100 kids)
- 27.79 1.00 1.00 0.99 12.50 Map window via parent (200 kids)
- 22.35 1.00 1.00 1.00 56.19 Unmap window via parent (4 kids)
- 9.57 1.00 0.99 1.00 89.78 Unmap window via parent (16 kids)
- 80.77 1.01 1.00 1.00 103.85 Unmap window via parent (25 kids)
- 96.34 1.00 1.00 1.00 116.06 Unmap window via parent (50 kids)
- 99.72 1.00 1.00 1.00 124.93 Unmap window via parent (75 kids)
- 112.36 1.00 1.00 1.00 125.27 Unmap window via parent (100 kids)
- 105.41 1.00 1.00 0.99 120.00 Unmap window via parent (200 kids)
- 51.29 1.03 1.02 1.02 74.19 Destroy window via parent (4 kids)
- 86.75 0.99 0.99 0.99 116.87 Destroy window via parent (16 kids)
- 106.43 1.01 1.01 1.01 127.49 Destroy window via parent (25 kids)
- 120.34 1.01 1.01 1.00 140.11 Destroy window via parent (50 kids)
- 126.67 1.00 0.99 0.99 145.00 Destroy window via parent (75 kids)
- 126.11 1.01 1.01 1.00 140.56 Destroy window via parent (100 kids)
- 128.57 1.01 1.00 1.00 137.91 Destroy window via parent (200 kids)
- 16.04 0.88 1.00 1.00 20.36 Hide/expose window via popup (4 kids)
- 19.04 1.01 1.00 1.00 23.48 Hide/expose window via popup (16 kids)
- 19.22 1.00 1.00 1.00 20.44 Hide/expose window via popup (25 kids)
- 17.41 1.00 0.91 0.97 17.68 Hide/expose window via popup (50 kids)
- 17.29 1.01 1.00 1.01 17.07 Hide/expose window via popup (75 kids)
- 16.74 1.00 1.00 1.00 16.17 Hide/expose window via popup (100 kids)
- 10.30 1.00 1.00 1.00 10.51 Hide/expose window via popup (200 kids)
- 16.48 1.01 1.00 1.00 26.05 Move window (4 kids)
- 17.01 0.95 1.00 1.00 23.97 Move window (16 kids)
- 16.95 1.00 1.00 1.00 22.90 Move window (25 kids)
- 16.05 1.01 1.00 1.00 21.32 Move window (50 kids)
- 15.58 1.00 0.98 0.98 19.44 Move window (75 kids)
- 14.98 1.02 1.03 1.03 18.17 Move window (100 kids)
- 10.90 1.01 1.01 1.00 12.68 Move window (200 kids)
- 49.42 1.00 1.00 1.00 198.27 Moved unmapped window (4 kids)
- 50.72 0.97 1.00 1.00 193.66 Moved unmapped window (16 kids)
- 50.87 1.00 0.99 1.00 195.09 Moved unmapped window (25 kids)
- 50.72 1.00 1.00 1.00 189.34 Moved unmapped window (50 kids)
- 50.87 1.00 1.00 1.00 191.33 Moved unmapped window (75 kids)
- 50.87 1.00 1.00 0.90 186.71 Moved unmapped window (100 kids)
- 50.87 1.00 1.00 1.00 179.19 Moved unmapped window (200 kids)
- 41.04 1.00 1.00 1.00 56.61 Move window via parent (4 kids)
- 69.81 1.00 1.00 1.00 130.82 Move window via parent (16 kids)
- 95.81 1.00 1.00 1.00 141.92 Move window via parent (25 kids)
- 95.98 1.00 1.00 1.00 149.43 Move window via parent (50 kids)
- 96.59 1.01 1.01 1.00 153.98 Move window via parent (75 kids)
- 97.19 1.00 1.00 1.00 157.30 Move window via parent (100 kids)
- 96.67 1.00 0.99 0.96 159.44 Move window via parent (200 kids)
- 17.75 1.01 1.00 1.00 27.61 Resize window (4 kids)
- 17.94 1.00 1.00 0.99 25.42 Resize window (16 kids)
- 17.92 1.01 1.00 1.00 24.47 Resize window (25 kids)
- 17.24 0.97 1.00 1.00 24.14 Resize window (50 kids)
- 16.81 1.00 1.00 0.99 22.75 Resize window (75 kids)
- 16.08 1.00 1.00 1.00 21.20 Resize window (100 kids)
- 12.92 1.00 0.99 1.00 16.26 Resize window (200 kids)
- 52.94 1.01 1.00 1.00 327.12 Resize unmapped window (4 kids)
- 53.60 1.01 1.01 1.01 333.71 Resize unmapped window (16 kids)
- 52.99 1.00 1.00 1.00 337.29 Resize unmapped window (25 kids)
- 51.98 1.00 1.00 1.00 329.38 Resize unmapped window (50 kids)
- 53.05 0.89 1.00 1.00 322.60 Resize unmapped window (75 kids)
- 53.05 1.00 1.00 1.00 318.08 Resize unmapped window (100 kids)
- 53.11 1.00 1.00 0.99 306.21 Resize unmapped window (200 kids)
- 16.76 1.00 0.96 1.00 19.46 Circulate window (4 kids)
- 17.24 1.00 1.00 0.97 16.24 Circulate window (16 kids)
- 16.30 1.03 1.03 1.03 15.85 Circulate window (25 kids)
- 13.45 1.00 1.00 1.00 14.90 Circulate window (50 kids)
- 12.91 1.00 1.00 1.00 13.06 Circulate window (75 kids)
- 11.30 0.98 1.00 1.00 11.03 Circulate window (100 kids)
- 7.58 1.01 1.01 0.99 7.47 Circulate window (200 kids)
- 1.01 1.01 0.98 1.00 0.95 Circulate Unmapped window (4 kids)
- 1.07 1.07 1.01 1.07 1.02 Circulate Unmapped window (16 kids)
- 1.04 1.09 1.06 1.05 0.97 Circulate Unmapped window (25 kids)
- 1.04 1.23 1.20 1.18 1.05 Circulate Unmapped window (50 kids)
- 1.18 1.53 1.19 1.45 1.24 Circulate Unmapped window (75 kids)
- 1.08 1.02 1.01 1.74 1.01 Circulate Unmapped window (100 kids)
- 1.01 1.12 0.98 0.91 0.97 Circulate Unmapped window (200 kids)
-
-
-
- BB..22..88.. PPrrooffiilliinngg wwiitthh OOPPrrooffiillee
-
- OProfile (available from http://oprofile.sourceforge.net/) is a
- system-wide profiler for Linux systems that uses processor-level
- counters to collect sampling data. OProfile can provide information
- that is similar to that provided by gprof, but without the necessity
- of recompiling the program with special instrumentation (i.e.,
- OProfile can collect statistical profiling information about optimized
- programs). A test harness was developed to collect OProfile data for
- each x11perf test individually.
-
-
- Test runs were performed using the RETIRED_INSNS counter on the AMD
- Athlon and the CPU_CLK_HALTED counter on the Intel Pentium III (with a
- test configuration different from the one described above). We have
- examined OProfile output and have compared it with gprof output. This
- investigation has not produced results that yield performance
- increases in x11perf numbers.
-
-
-
- BB..22..99.. XX TTeesstt SSuuiittee
-
- The X Test Suite was run on the fully optimized DMX server using the
- configuration described above. The following failures were noted:
-
- XListPixmapFormats: Test 1 [1]
- XChangeWindowAttributes: Test 32 [1]
- XCreateWindow: Test 30 [1]
- XFreeColors: Test 4 [3]
- XCopyArea: Test 13, 17, 21, 25, 30 [2]
- XCopyPlane: Test 11, 15, 27, 31 [2]
- XSetFontPath: Test 4 [1]
- XChangeKeyboardControl: Test 9, 10 [1]
-
- [1] Previously documented errors expected from the Xinerama
- implementation (see Phase I discussion).
- [2] Newly noted errors that have been verified as expected
- behavior of the Xinerama implementation.
- [3] Newly noted error that has been verified as a Xinerama
- implementation bug.
-
-
-
- BB..33.. PPhhaassee IIIIII
-
- During the third phase of development, support was provided for the
- following extensions: SHAPE, RENDER, XKEYBOARD, XInput.
-
-
- BB..33..11.. SSHHAAPPEE
-
- The SHAPE extension is supported. Test applications (e.g., xeyes and
- oclock) and window managers that make use of the SHAPE extension will
- work as expected.
-
-
- BB..33..22.. RREENNDDEERR
-
- The RENDER extension is supported. The version included in the DMX
- CVS tree is version 0.2, and this version is fully supported by Xdmx.
- Applications using only version 0.2 functions will work correctly;
- however, some apps that make use of functions from later versions do
- not properly check the extension's major/minor version numbers. These
- apps will fail with a Bad Implementation error when using post-version
- 0.2 functions. This is expected behavior. When the DMX CVS tree is
- updated to include newer versions of RENDER, support for these newer
- functions will be added to the DMX X server.
-
-
- BB..33..33.. XXKKEEYYBBOOAARRDD
-
- The XKEYBOARD extension is supported. If present on the back-end X
- servers, the XKEYBOARD extension will be used to obtain information
- about the type of the keyboard for initialization. Otherwise, the
- keyboard will be initialized using defaults. Note that this departs
- from older behavior: when Xdmx is compiled without XKEYBOARD support,
- the map from the back-end X server will be preserved. With XKEYBOARD
- support, the map is not preserved because better information and
- control of the keyboard is available.
-
-
- BB..33..44.. XXIInnppuutt
-
- The XInput extension is supported. Any device can be used as a core
- device and be used as an XInput extension device, with the exception
- of core devices on the back-end servers. This limitation is present
- because cursor handling on the back-end requires that the back-end
- cursor sometimes track the Xdmx core cursor -- behavior that is
- incompatible with using the back-end pointer as a non-core device.
-
-
- Currently, back-end extension devices are not available as Xdmx
- extension devices, but this limitation should be removed in the
- future.
-
-
- To demonstrate the XInput extension, and to provide more examples for
- low-level input device driver writers, USB device drivers have been
- written for mice (usb-mou), keyboards (usb-kbd), and non-mouse/non-
- keyboard USB devices (usb-oth). Please see the man page for
- information on Linux kernel drivers that are required for using these
- Xdmx drivers.
-
-
- BB..33..55.. DDPPMMSS
-
- The DPMS extension is exported but does not do anything at this time.
-
-
- BB..33..66.. OOtthheerr EExxtteennssiioonnss
-
- The LBX, SECURITY, XC-APPGROUP, and XFree86-Bigfont extensions do not
- require any special Xdmx support and have been exported.
-
-
- The BIG-REQUESTS, DEC-XTRAP, DOUBLE-BUFFER, Extended-Visual-
- Information, FontCache, GLX, MIT-SCREEN-SAVER, MIT-SHM, MIT-SUNDRY-
- NONSTANDARD, RECORD, SECURITY, SGI-GLX, SYNC, TOG-CUP, X-Resource, XC-
- MISC, XFree86-DGA, XFree86-DRI, XFree86-Misc,
- XFree86-VidModeExtension, and XVideo extensions are _n_o_t supported at
- this time, but will be evaluated for inclusion in future DMX releases.
- SSeeee bbeellooww ffoorr aaddddiittiioonnaall wwoorrkk oonn eexxtteennssiioonnss aafftteerr PPhhaassee IIIIII..
-
-
- BB..44.. PPhhaassee IIVV
-
- BB..44..11.. MMoovviinngg ttoo XXFFrreeee8866 44..33..00
-
- For Phase IV, the recent release of XFree86 4.3.0 (27 February 2003)
- was merged onto the dmx.sourceforge.net CVS trunk and all work is
- proceeding using this tree.
-
-
- BB..44..22.. EExxtteennssiioonnss
-
- BB..44..22..11.. XXCC--MMIISSCC ((ssuuppppoorrtteedd))
-
- XC-MISC is used internally by the X library to recycle XIDs from the X
- server. This is important for long-running X server sessions. Xdmx
- supports this extension. The X Test Suite passed and failed the exact
- same tests before and after this extension was enabled.
-
-
- BB..44..22..22.. EExxtteennddeedd--VViissuuaall--IInnffoorrmmaattiioonn ((ssuuppppoorrtteedd))
-
- The Extended-Visual-Information extension provides a method for an X
- client to obtain detailed visual information. Xdmx supports this
- extension. It was tested using the hw/dmx/examples/evi example
- program. NNoottee tthhaatt tthhiiss eexxtteennssiioonn iiss nnoott XXiinneerraammaa--aawwaarree -- it will
- return visual information for each screen even though Xinerama is
- causing the X server to export a single logical screen.
-
-
- BB..44..22..33.. RREESS ((ssuuppppoorrtteedd))
-
- The X-Resource extension provides a mechanism for a client to obtain
- detailed information about the resources used by other clients. This
- extension was tested with the hw/dmx/examples/res program. The X Test
- Suite passed and failed the exact same tests before and after this
- extension was enabled.
-
-
- BB..44..22..44.. BBIIGG--RREEQQUUEESSTTSS ((ssuuppppoorrtteedd))
-
- This extension enables the X11 protocol to handle requests longer than
- 262140 bytes. The X Test Suite passed and failed the exact same tests
- before and after this extension was enabled.
-
-
- BB..44..22..55.. XXSSYYNNCC ((ssuuppppoorrtteedd))
-
- This extension provides facilities for two different X clients to
- synchronize their requests. This extension was minimally tested with
- xdpyinfo and the X Test Suite passed and failed the exact same tests
- before and after this extension was enabled.
-
-
- BB..44..22..66.. XXTTEESSTT,, RREECCOORRDD,, DDEECC--XXTTRRAAPP ((ssuuppppoorrtteedd)) aanndd XXTTeessttEExxtteennssiioonn11
- ((nnoott ssuuppppoorrtteedd))
-
- The XTEST and RECORD extension were developed by the X Consortium for
- use in the X Test Suite and are supported as a standard in the X11R6
- tree. They are also supported in Xdmx. When X Test Suite tests that
- make use of the XTEST extension are run, Xdmx passes and fails exactly
- the same tests as does a standard XFree86 X server. When the rcrdtest
- test (a part of the X Test Suite that verifies the RECORD extension)
- is run, Xdmx passes and fails exactly the same tests as does a
- standard XFree86 X server.
-
-
- There are two older XTEST-like extensions: DEC-XTRAP and
- XTestExtension1. The XTestExtension1 extension was developed for use
- by the X Testing Consortium for use with a test suite that eventually
- became (part of?) the X Test Suite. Unlike XTEST, which only allows
- events to be sent to the server, the XTestExtension1 extension also
- allowed events to be recorded (similar to the RECORD extension). The
- second is the DEC-XTRAP extension that was developed by the Digital
- Equipment Corporation.
-
-
- The DEC-XTRAP extension is available from Xdmx and has been tested
- with the xtrap* tools which are distributed as standard X11R6 clients.
-
-
- The XTestExtension1 is _n_o_t supported because it does not appear to be
- used by any modern X clients (the few that support it also support
- XTEST) and because there are no good methods available for testing
- that it functions correctly (unlike XTEST and DEC-XTRAP, the code for
- XTestExtension1 is not part of the standard X server source tree, so
- additional testing is important).
-
-
- Most of these extensions are documented in the X11R6 source tree.
- Further, several original papers exist that this author was unable to
- locate -- for completeness and historical interest, citations are
- provide:
-
- XXRREECCOORRDD
- Martha Zimet. Extending X For Recording. 8th Annual X Technical
- Conference Boston, MA January 24-26, 1994.
-
- DDEECC--XXTTRRAAPP
- Dick Annicchiarico, Robert Chesler, Alan Jamison. XTrap
- Architecture. Digital Equipment Corporation, July 1991.
-
- XXTTeessttEExxtteennssiioonn11
- Larry Woestman. X11 Input Synthesis Extension Proposal. Hewlett
- Packard, November 1991.
-
-
- BB..44..22..77.. MMIITT--MMIISSCC ((nnoott ssuuppppoorrtteedd))
-
- The MIT-MISC extension is used to control a bug-compatibility flag
- that provides compatibility with xterm programs from X11R1 and X11R2.
- There does not appear to be a single client available that makes use
- of this extension and there is not way to verify that it works
- correctly. The Xdmx server does _n_o_t support MIT-MISC.
-
-
- BB..44..22..88.. SSCCRREEEENNSSAAVVEERR ((nnoott ssuuppppoorrtteedd))
-
- This extension provides special support for the X screen saver. It
- was tested with beforelight, which appears to be the only client that
- works with it. When Xinerama was not active, beforelight behaved as
- expected. However, when Xinerama was active, beforelight did not
- behave as expected. Further, when this extension is not active,
- xscreensaver (a widely-used X screen saver program) did not behave as
- expected. Since this extension is not Xinerama-aware and is not
- commonly used with expected results by clients, we have left this
- extension disabled at this time.
-
- BB..44..22..99.. GGLLXX ((ssuuppppoorrtteedd))
-
- The GLX extension provides OpenGL and GLX windowing support. In Xdmx,
- the extension is called glxProxy, and it is Xinerama aware. It works
- by either feeding requests forward through Xdmx to each of the back-
- end servers or handling them locally. All rendering requests are
- handled on the back-end X servers. This code was donated to the DMX
- project by SGI. For the X Test Suite results comparison, see below.
-
-
- BB..44..22..1100.. RREENNDDEERR ((ssuuppppoorrtteedd))
-
- The X Rendering Extension (RENDER) provides support for digital image
- composition. Geometric and text rendering are supported. RENDER is
- partially Xinerama-aware, with text and the most basic compositing
- operator; however, its higher level primitives (triangles, triangle
- strips, and triangle fans) are not yet Xinerama-aware. The RENDER
- extension is still under development, and is currently at version 0.8.
- Additional support will be required in DMX as more primitives and/or
- requests are added to the extension.
-
-
- There is currently no test suite for the X Rendering Extension;
- however, there has been discussion of developing a test suite as the
- extension matures. When that test suite becomes available, additional
- testing can be performed with Xdmx. The X Test Suite passed and
- failed the exact same tests before and after this extension was
- enabled.
-
-
- BB..44..22..1111.. SSuummmmaarryy
-
- To summarize, the following extensions are currently supported: BIG-
- REQUESTS, DEC-XTRAP, DMX, DPMS, Extended-Visual-Information, GLX, LBX,
- RECORD, RENDER, SECURITY, SHAPE, SYNC, X-Resource, XC-APPGROUP, XC-
- MISC, XFree86-Bigfont, XINERAMA, XInputExtension, XKEYBOARD, and
- XTEST.
-
-
- The following extensions are _n_o_t supported at this time: DOUBLE-
- BUFFER, FontCache, MIT-SCREEN-SAVER, MIT-SHM, MIT-SUNDRY-NONSTANDARD,
- TOG-CUP, XFree86-DGA, XFree86-Misc, XFree86-VidModeExtension,
- XTestExtensionExt1, and XVideo.
-
-
- BB..44..33.. AAddddiittiioonnaall TTeessttiinngg wwiitthh tthhee XX TTeesstt SSuuiittee
-
- BB..44..33..11.. XXFFrreeee8866 wwiitthhoouutt XXTTEESSTT
-
- After the release of XFree86 4.3.0, we retested the XFree86 X server
- with and without using the XTEST extension. When the XTEST extension
- was _n_o_t used for testing, the XFree86 4.3.0 server running on our
- usual test system with a Radeon VE card reported unexpected failures
- in the following tests:
-
- XListPixmapFormats: Test 1
- XChangeKeyboardControl: Tests 9, 10
- XGetDefault: Test 5
- XRebindKeysym: Test 1
-
-
-
- BB..44..33..22.. XXFFrreeee8866 wwiitthh XXTTEESSTT
-
- When using the XTEST extension, the XFree86 4.3.0 server reported the
- following errors:
-
- XListPixmapFormats: Test 1
- XChangeKeyboardControl: Tests 9, 10
- XGetDefault: Test 5
- XRebindKeysym: Test 1
-
- XAllowEvents: Tests 20, 21, 24
- XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
- XGrabKey: Test 8
- XSetPointerMapping: Test 3
- XUngrabButton: Test 4
-
-
-
- While these errors may be important, they will probably be fixed
- eventually in the XFree86 source tree. We are particularly interested
- in demonstrating that the Xdmx server does not introduce additional
- failures that are not known Xinerama failures.
-
-
- BB..44..33..33.. XXddmmxx wwiitthh XXTTEESSTT,, wwiitthhoouutt XXiinneerraammaa,, wwiitthhoouutt GGLLXX
-
- Without Xinerama, but using the XTEST extension, the following errors
- were reported from Xdmx (note that these are the same as for the
- XFree86 4.3.0, except that XGetDefault no longer fails):
-
- XListPixmapFormats: Test 1
- XChangeKeyboardControl: Tests 9, 10
- XRebindKeysym: Test 1
-
- XAllowEvents: Tests 20, 21, 24
- XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
- XGrabKey: Test 8
- XSetPointerMapping: Test 3
- XUngrabButton: Test 4
-
-
-
- BB..44..33..44.. XXddmmxx wwiitthh XXTTEESSTT,, wwiitthh XXiinneerraammaa,, wwiitthhoouutt GGLLXX
-
- With Xinerama, using the XTEST extension, the following errors were
- reported from Xdmx:
-
- XListPixmapFormats: Test 1
- XChangeKeyboardControl: Tests 9, 10
- XRebindKeysym: Test 1
-
- XAllowEvents: Tests 20, 21, 24
- XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
- XGrabKey: Test 8
- XSetPointerMapping: Test 3
- XUngrabButton: Test 4
-
- XCopyPlane: Tests 13, 22, 31 (well-known XTEST/Xinerama interaction issue)
- XDrawLine: Test 67
- XDrawLines: Test 91
- XDrawSegments: Test 68
-
-
-
- Note that the first two sets of errors are the same as for the XFree86
- 4.3.0 server, and that the XCopyPlane error is a well-known error
- resulting from an XTEST/Xinerama interaction when the request crosses
- a screen boundary. The XDraw* errors are resolved when the tests are
- run individually and they do not cross a screen boundary. We will
- investigate these errors further to determine their cause.
-
-
- BB..44..33..55.. XXddmmxx wwiitthh XXTTEESSTT,, wwiitthh XXiinneerraammaa,, wwiitthh GGLLXX
-
- With GLX enabled, using the XTEST extension, the following errors were
- reported from Xdmx (these results are from early during the Phase IV
- development, but were confirmed with a late Phase IV snapshot):
-
- XListPixmapFormats: Test 1
- XChangeKeyboardControl: Tests 9, 10
- XRebindKeysym: Test 1
-
- XAllowEvents: Tests 20, 21, 24
- XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
- XGrabKey: Test 8
- XSetPointerMapping: Test 3
- XUngrabButton: Test 4
-
- XClearArea: Test 8
- XCopyArea: Tests 4, 5, 11, 14, 17, 23, 25, 27, 30
- XCopyPlane: Tests 6, 7, 10, 19, 22, 31
- XDrawArcs: Tests 89, 100, 102
- XDrawLine: Test 67
- XDrawSegments: Test 68
-
-
- Note that the first two sets of errors are the same as for the XFree86
- 4.3.0 server, and that the third set has different failures than when
- Xdmx does not include GLX support. Since the GLX extension adds new
- visuals to support GLX's visual configs and the X Test Suite runs
- tests over the entire set of visuals, additional rendering tests were
- run and presumably more of them crossed a screen boundary. This con-
- clusion is supported by the fact that nearly all of the rendering
- errors reported are resolved when the tests are run individually and
- they do no cross a screen boundary.
-
-
- Further, when hardware rendering is disabled on the back-end displays,
- many of the errors in the third set are eliminated, leaving only:
-
- XClearArea: Test 8
- XCopyArea: Test 4, 5, 11, 14, 17, 23, 25, 27, 30
- XCopyPlane: Test 6, 7, 10, 19, 22, 31
-
-
-
- BB..44..33..66.. CCoonncclluussiioonn
-
- We conclude that all of the X Test Suite errors reported for Xdmx are
- the result of errors in the back-end X server or the Xinerama
- implementation. Further, all of these errors that can be reasonably
- fixed at the Xdmx layer have been. (Where appropriate, we have
- submitted patches to the XFree86 and Xinerama upstream maintainers.)
-
-
- BB..44..44.. DDyynnaammiicc RReeccoonnffiigguurraattiioonn
-
- During this development phase, dynamic reconfiguration support was
- added to DMX. This support allows an application to change the
- position and offset of a back-end server's screen. For example, if
- the application would like to shift a screen slightly to the left, it
- could query Xdmx for the screen's <x,y> position and then dynamically
- reconfigure that screen to be at position <x+10,y>. When a screen is
- dynamically reconfigured, input handling and a screen's root window
- dimensions are adjusted as needed. These adjustments are transparent
- to the user.
-
-
- BB..44..44..11.. DDyynnaammiicc rreeccoonnffiigguurraattiioonn eexxtteennssiioonn
-
- The application interface to DMX's dynamic reconfiguration is through
- a function in the DMX extension library:
-
- Bool DMXReconfigureScreen(Display *dpy, int screen, int x, int y)
-
-
- where _d_p_y is DMX server's display, _s_c_r_e_e_n is the number of the screen
- to be reconfigured, and _x and _y are the new upper, left-hand coordi-
- nates of the screen to be reconfigured.
-
-
- The coordinates are not limited other than as required by the X
- protocol, which limits all coordinates to a signed 16 bit number. In
- addition, all coordinates within a screen must also be legal values.
- Therefore, setting a screen's upper, left-hand coordinates such that
- the right or bottom edges of the screen is greater than 32,767 is
- illegal.
-
-
- BB..44..44..22.. BBoouunnddiinngg bbooxx
-
- When the Xdmx server is started, a bounding box is calculated from the
- screens' layout given either on the command line or in the
- configuration file. This bounding box is currently fixed for the
- lifetime of the Xdmx server.
-
-
- While it is possible to move a screen outside of the bounding box, it
- is currently not possible to change the dimensions of the bounding
- box. For example, it is possible to specify coordinates of
- <-100,-100> for the upper, left-hand corner of the bounding box, which
- was previously at coordinates <0,0>. As expected, the screen is moved
- down and to the right; however, since the bounding box is fixed, the
- left side and upper portions of the screen exposed by the
- reconfiguration are no longer accessible on that screen. Those
- inaccessible regions are filled with black.
-
-
- This fixed bounding box limitation will be addressed in a future
- development phase.
-
-
- BB..44..44..33.. SSaammppllee aapppplliiccaattiioonnss
-
- An example of where this extension is useful is in setting up a video
- wall. It is not always possible to get everything perfectly aligned,
- and sometimes the positions are changed (e.g., someone might bump into
- a projector). Instead of physically moving projectors or monitors, it
- is now possible to adjust the positions of the back-end server's
- screens using the dynamic reconfiguration support in DMX.
-
-
- Other applications, such as automatic setup and calibration tools, can
- make use of dynamic reconfiguration to correct for projector alignment
- problems, as long as the projectors are still arranged rectilinearly.
- Horizontal and vertical keystone correction could be applied to
- projectors to correct for non-rectilinear alignment problems; however,
- this must be done external to Xdmx.
-
-
- A sample test program is included in the DMX server's examples
- directory to demonstrate the interface and how an application might
- use dynamic reconfiguration. See dmxreconfig.c for details.
-
-
- BB..44..44..44.. AAddddiittiioonnaall nnootteess
-
- In the original development plan, Phase IV was primarily devoted to
- adding OpenGL support to DMX; however, SGI became interested in the
- DMX project and developed code to support OpenGL/GLX. This code was
- later donated to the DMX project and integrated into the DMX code
- base, which freed the DMX developers to concentrate on dynamic
- reconfiguration (as described above).
-
-
- BB..44..55.. DDooxxyyggeenn ddooccuummeennttaattiioonn
-
- Doxygen is an open-source (GPL) documentation system for generating
- browseable documentation from stylized comments in the source code.
- We have placed all of the Xdmx server and DMX protocol source code
- files under Doxygen so that comprehensive documentation for the Xdmx
- source code is available in an easily browseable format.
-
-
- BB..44..66.. VVaallggrriinndd
-
- Valgrind, an open-source (GPL) memory debugger for Linux, was used to
- search for memory management errors. Several memory leaks were
- detected and repaired. The following errors were not addressed:
-
- 1. When the X11 transport layer sends a reply to the client, only
- those fields that are required by the protocol are filled in --
- unused fields are left as uninitialized memory and are therefore
- noted by valgrind. These instances are not errors and were not
- repaired.
-
- 2. At each server generation, glxInitVisuals allocates memory that is
- never freed. The amount of memory lost each generation
- approximately equal to 128 bytes for each back-end visual. Because
- the code involved is automatically generated, this bug has not been
- fixed and will be referred to SGI.
-
- 3. At each server generation, dmxRealizeFont calls XLoadQueryFont,
- which allocates a font structure that is not freed.
- dmxUnrealizeFont can free the font structure for the first screen,
- but cannot free it for the other screens since they are already
- closed by the time dmxUnrealizeFont could free them. The amount of
- memory lost each generation is approximately equal to 80 bytes per
- font per back-end. When this bug is fixed in the the X server's
- device-independent (dix) code, DMX will be able to properly free
- the memory allocated by XLoadQueryFont.
-
-
- BB..44..77.. RRAATTSS
-
- RATS (Rough Auditing Tool for Security) is an open-source (GPL)
- security analysis tool that scans source code for common security-
- related programming errors (e.g., buffer overflows and TOCTOU races).
- RATS was used to audit all of the code in the hw/dmx directory and all
- "High" notations were checked manually. The code was either re-
- written to eliminate the warning, or a comment containing "RATS" was
- inserted on the line to indicate that a human had checked the code.
- Unrepaired warnings are as follows:
-
- 1. Fixed-size buffers are used in many areas, but code has been added
- to protect against buffer overflows (e.g., XmuSnprint). The only
- instances that have not yet been fixed are in config/xdmxconfig.c
- (which is not part of the Xdmx server) and input/usb-common.c.
-
- 2. vprintf and vfprintf are used in the logging routines. In general,
- all uses of these functions (e.g., dmxLog) provide a constant
- format string from a trusted source, so the use is relatively
- benign.
-
- 3. glxProxy/glxscreens.c uses getenv and strcat. The use of these
- functions is safe and will remain safe as long as ExtensionsString
- is longer then GLXServerExtensions (ensuring this may not be ovious
- to the casual programmer, but this is in automatically generated
- code, so we hope that the generator enforces this constraint).
-
-
-
diff --git a/hw/dmx/doc/scaled.text b/hw/dmx/doc/scaled.text
new file mode 100644
index 0000000..d30105d
--- /dev/null
+++ b/hw/dmx/doc/scaled.text
@@ -0,0 +1,579 @@
+ Scaled Window Support in DMX
+ Rickard E. Faith and Kevin E. Martin
+ 15 October 2003 (created 19 September 2003)
+
+ This document investigates the possibility of adding scaled window
+ support to the DMX X server, thereby allowing a window or some
+ selected part of the logical DMX area to be displayed using a scaling
+ factor. For example, this might allow the contents of a window to be
+ magnified for easier viewing. In particular, scaling for the VNC
+ client is explored. _C_o_p_y_r_i_g_h_t _2_0_0_3 _b_y _R_e_d _H_a_t_, _I_n_c_._, _R_a_l_e_i_g_h_, _N_o_r_t_h
+ _C_a_r_o_l_i_n_a
+
+ ______________________________________________________________________
+
+ Table of Contents
+
+
+ 1. Introduction
+ 1.1 DMX
+ 1.2 Problem Statement
+ 1.3 Task
+
+ 2. Previous Work
+ 2.1 VNC
+ 2.1.1 Scaling under VNC
+ 2.2 The X Video Extension
+
+ 3. Possible Solutions
+ 3.1 VNC-like Scaling
+ 3.1.1 Software Scaling
+ 3.1.2 Scaling with the X Video Extension
+ 3.1.2.1 Implementing the X Video Extension for DMX
+ 3.1.2.2 Supporting RGB formats for the X Video Extension
+ 3.1.3 Scaling with an XPutImageScaled Extension
+ 3.1.4 Scaling with an XCopyAreaScaled Extension
+ 3.1.5 Scaling with OpenGL
+ 3.2 Application-transparent Scaling for DMX
+ 3.2.1 Back-end Scaling Without Disconnect/Reconnect
+ 3.2.2 Back-end Scaling With Disconnect/Reconnect
+ 3.2.3 Server-side Scaling
+ 3.3 XCreateScaledWindow API
+ 3.3.1 XCreateWindow
+ 3.3.2 XSetWindowAttributes
+ 3.3.3 XGetWindowAttributes, XGetGeometry
+ 3.3.4 Popup and Child window positions
+ 3.3.5 Events
+ 3.3.6 Implementation
+
+ 4. Conclusion and Recommendations
+
+
+ ______________________________________________________________________
+
+ 11.. IInnttrroodduuccttiioonn
+
+ 11..11.. DDMMXX
+
+ The DMX X server (Xdmx) is a proxy server that is designed to allow X
+ servers on multiple machines to be combined into a single multi-headed
+ X server. Combined with Xinerama, these heads can appear as a single
+ very high-resolution screen. Typical applications include the
+ creation of a video wall with 16 1280x1024 displays arranged in a
+ rectangle, for a total resolution of of 5120x4096.
+
+
+
+ 11..22.. PPrroobblleemm SSttaatteemmeenntt
+
+ Applications displayed on a physically large video wall that provides
+ high pixel-resolution may be difficult to see, especially if the
+ application is designed for use on a typical desktop computer with a
+ relatively small display located close to the human operator. The
+ goal of this paper is to describe and discuss solutions to this
+ problem.
+
+ The original driving problem for this work is to provide scaling for
+ the vncviewer application when displayed using DMX (VNC scaling is
+ currently available only with the Windows client, and there is no plan
+ to extend that capability to other clients). While this specific
+ problem will be addressed in this paper, the general solution space
+ will also be explored, since this may lead to a good solution not only
+ for vncviewer but also for other applications.
+
+ 11..33.. TTaasskk
+
+ For reference, here is the original description of the task this paper
+ addresses:
+
+ +o Scaled window support (for VNC)
+
+ +o Investigate possibility of implementing a "scaled window"
+ extension:
+
+ +o Add XCreateScaledWindow call that could be used in place of
+ XCreateWindow
+
+ +o All primitives drawn to scaled window would be scaled by
+ appropriate (integral?) scaling factor
+
+ +o Alternate approach: special case VNC support
+
+ 22.. PPrreevviioouuss WWoorrkk
+
+ This section reviews relevant previous work.
+
+ 22..11.. VVNNCC
+
+ 22..11..11.. SSccaalliinngg uunnddeerr VVNNCC
+
+ When using the vncviewer program for Windows, it is possible to
+ specify a scaling factor (as numerator and denominator). When scaling
+ is in effect, the viewer software uses StretchBlt (instead of BitBlt)
+ to display the pixels for the user. When this call is made, the
+ viewer already has received all of the pixel information (at full
+ unscaled resolution).
+
+ The scaling in VNC is primitive. It does not conserve bandwidth, it
+ does not treat textual information differently (i.e., by using a
+ suitably scaled font), and it does not provide any anti-aliasing other
+ than that provided by the underlying (Windows-only) system library.
+
+ 22..22.. TThhee XX VViiddeeoo EExxtteennssiioonn
+
+ The X Video Extension is a widely-available extension to the X11
+ protocol that provides support for streaming video. Integral to this
+ support is the ability to arbitrarily scale the output. In version
+ 2.2 of the X Video specification, support for scaled still images was
+ provided, using both shared memory and traditional transport. The API
+ for this support uses calls that are quite similar to XCreateWindow,
+ XPutImage, and XShmPutImage. Currently, most of the drivers
+ implemented in XFree86 only support data in various YUV formats.
+ However, several modern video adaptors support RGB as well.
+ Note, though, that the target output for this scaling is an overlay
+ plane -- so X Video provides functionality that is fundamentally
+ different from that provided by the Windows StrechBlt call.
+
+ 33.. PPoossssiibbllee SSoolluuttiioonnss
+
+ This section briefly discusses possible solutions, including major
+ advantages and disadvantages from both the implementation and the end-
+ user programmer standpoint.
+
+ 33..11.. VVNNCC--lliikkee SSccaalliinngg
+
+ 33..11..11.. SSooffttwwaarree SSccaalliinngg
+
+ The vncviewer application could be modified to provide software
+ scaling. This is not a general solution, but it does solve one of the
+ goals of this work.
+
+ A prototype of this solution was implemented and a patch against
+ vnc-3.3.7-unixsrc is available in the dmx/external directory. Because
+ of limited time available for this work, all of the edge cases were
+ not considered and the solution works well mainly for integer scaling.
+
+ Currently, vncviewer writes to the X display with XPutImage,
+ XCopyArea, and XFillRectangle. All instances of these calls have to
+ be aware of scaling and must round correctly. In the prototype
+ solution, rounding is incorrect and can cause artifacts.
+
+ A better solution would be to cache all updates to the desktop image
+ in vncviewer and only send the damaged area to the X display with
+ XPutImage. This would allow the damaged area to be computed so that
+ rounding errors do not create artifacts. This method is probably
+ similar to what is used in the Window client. (The whole VNC suite is
+ being re-written in C++ and the forthcoming version 4 has not been
+ evaluated.)
+
+ 33..11..22.. SSccaalliinngg wwiitthh tthhee XX VViiddeeoo EExxtteennssiioonn
+
+ The scaling in the Windows vncviewer application makes use of a scaled
+ blit that is supplied by the underlying system library. Several video
+ cards currently provide support for a scaled blit, and some X servers
+ (including XFree86) expose this capability to applications via the
+ XvPutImage interface of the X Video Extension. The capability exposed
+ by XvPutImage results in the scaled image being drawn to an overlay
+ plane. Most video cards also provide support for a scaled blit into
+ the normal output planes, but this is not exposed via XvPutImage.
+
+ The vncviewer program could be modified to use the X Video Extension
+ to provide scaling under X11 that is similar to the scaling currently
+ provided under Windows. Unfortunately, Xdmx does not currently export
+ the X Video Extension, so this would not provide an immediate solution
+ usable with DMX.
+
+ A very early-stage proof-of-concept prototype was implemented and a
+ preliminary patch against vnc-3.3.7-unixsrc is available in the
+ dmx/external directory. This prototype was implemented to better
+ understand the problems that must be solved to make this solution
+ viable:
+
+ +o As noted under the software scaling section above, vncviewer writes
+ to the X display with several different calls. These calls write
+ to the normal output planes and are compatible with XvPutImage,
+ which writes to an overlay plane. To eliminate artifacts caused by
+ this problem, vncviewer should be modified so that a cached copy of
+ the desktop is available, either as a client-side image or a
+ server-side off-screen pixmap, so that XvPutImage would be the only
+ method for writing to the X display.
+
+ +o
+
+ Although several modern graphics adaptors support hardware scaling
+ using an RGB format (e.g., ATI Radeon, nVidia, etc.), XFree86
+ drivers typically only implement YUV formats. YUV generally
+ compress the pixel information in some way. For example, two
+ commonly implemented formats, YUY2 and UYVY provide intensity
+ information for every RGB pixel, but only provide chroma and
+ luminance information for pairs of horizontal pixels. Since VNC
+ uses pixel-resolution for communicating updates on the wire,
+ additional artifacts are introduced (because there may not be
+ enough information from the wire to update a pair of pixels).
+
+ Further, the well-known problem with YUV encoding is even more
+ evident when the image is a desktop instead of a movie. For
+ example, consider a 1-pixel-wide vertical window border. If the
+ border changes in color but not intensity (e.g., because a window
+ manager uses color to indicate focus), there may or may not be a
+ change in the YUY2 image, depending on the algorithm used for RGB
+ to YUV conversion and on how the border pixel is ordered in the
+ pair of pixels used by the algorithm.
+
+ Many of these artifacts could be eliminated if vncviewer cached a
+ complete RGB image of the desktop, and only did the conversion to
+ YUV for properly aligned areas of damage. The remaining artifacts
+ could be eliminated if an RGB format was used with X Video (which
+ may require the extension of existing XFree86 drivers to support
+ RGB).
+
+ +o Most modern video cards support exactly one overlay plane that is
+ suitable for use with X Video. Therefore, only one application can
+ use X Video at any given time. This is a severe limitation in a
+ desktop environment.
+
+ 33..11..22..11.. IImmpplleemmeennttiinngg tthhee XX VViiddeeoo EExxtteennssiioonn ffoorr DDMMXX
+
+ The user-level API for X Video is fairly simple, but the underlying
+ support required for the full specification is large. However, since
+ the API provides a method to query supported capabilities, a usable
+ subset of X Video can be implemented that would support XvPutImage and
+ little else. This would require support for the following:
+
+ +o X Video Extension API calls, including the following:
+
+ +o XvQueryExtension
+
+ +o XvQueryAdaptors
+
+ +o XvQueryPortAttributes
+
+ +o XvFreeAdaptorInfo
+
+ +o XvListImageFormats
+
+ +o XvGrabPort
+
+ +o XvCreateImage
+
+ +o XvPutImage
+
+ +o XvShmCreateImage
+
+ +o XvShmPutImage
+
+ +o Support for querying back-end X Video Extension capabilities.
+
+ +o Support for sending the image to the back-ends. Because X Video
+ requires sending full images, there may be a trade-off between
+ bandwidth limitations and additional complexity to divide the image
+ up such that is scales properly.
+
+ +o Possible support for a software fall-back. For example, if all of
+ the back-ends do not support the X Video Extension, software
+ scaling can be implemented such that the image is sent to the back-
+ end with XPutImage. This pathway would have poor performance.
+
+ 33..11..22..22.. SSuuppppoorrttiinngg RRGGBB ffoorrmmaattss ffoorr tthhee XX VViiddeeoo EExxtteennssiioonn
+
+ Assuming an XFree86 driver already supports the X Video Extension, and
+ assuming the target hardware supports an RGB format, then adding
+ support for that format is relatively simple and straightforward.
+
+ 33..11..33.. SSccaalliinngg wwiitthh aann XXPPuuttIImmaaggeeSSccaalleedd EExxtteennssiioonn
+
+ Instead of (or in addition to) implementing the X Video Extension in
+ DMX, one obvious solution would be to implement a new extension that
+ provides access to hardware-assisted scaled blits, similar to the
+ StretchBlt call available under Windows. This call would scale RGB
+ images and would not use the overlay plane (unlike the X Video
+ Extension).
+
+ This approach has many of the same advantages and disadvantages as the
+ XCopyAreaScaled Extension, discussed in the next section. Discussion
+ of XPutImageScaled is deferred in favor of XCopyAreaScaled for the
+ following reasons:
+
+ +o XPutImageScaled can be emulated with XCopyAreaScaled by first using
+ XPutImage to copy the image to an off-screen pixmap, and then
+ calling XCopyAreaScaled between that off-screen pixmap and the
+ target drawable.
+
+ +o Since XCopyAreaScaled would copy between two areas of on-screen or
+ off-screen memory, it has additional uses and can be viewed as
+ efficiently providing a superset of XPutImageScaled functionality.
+
+ 33..11..44.. SSccaalliinngg wwiitthh aann XXCCooppyyAArreeaaSSccaalleedd EExxtteennssiioonn
+
+ As noted in the previous section, because XCopyAreaScaled provides a
+ superset of the functionality provided by XPutImageScaled, we will
+ consider this extension instead.
+
+ First, XCopyAreaScaled would provide for RGB scaling between pixmaps
+ (i.e., on-screen or off-screen areas of memory that reside on the
+ video card). Unlike the X Video Extension, which writes into an
+ overlay plane, XCopyAreaScaled would write into the non-overlay areas
+ of the screen. Key points to consider are as follows:
+
+ +o Because different planes are involved, the two scaling operations
+ are usually implemented in hardware differently, so an
+ XCopyAreaScaled extension could be added in a manner that would
+ neither conflict with nor interact with the X Video extension in
+ any way.
+
+ +o The XCopyAreaScaled extension provides new functionality that the X
+ Video Extension does not provide. Based on anecdotal feedback, we
+ believe that many people outside the DMX and VNC communities would
+ be excited about this extension.
+
+ +o The main drawback to this extension is that it is new and needs to
+ be implemented at the driver level in XFree86 for each video card
+ to be supported. At the present time, it is more likely that the X
+ Video Extension will be implemented for a particular piece hardware
+ because the X Video extension has multimedia uses. However, over
+ time, we would expect the XCopyAreaScaled extension to be
+ implemented along with the X Video extension, especially if it
+ becomes popular.
+
+ +o Another drawback is that not all modern cards provide support for a
+ simple scaled blit operation. However, these cards usually do
+ provide a 3D pipeline which could be used to provide this
+ functionality in a manner that is transparent to the client
+ application that is using the XCopyAreaScaled extension. However,
+ this implementation pathway would make this extension somewhat more
+ difficult to implement on certain cards.
+
+ 33..11..55.. SSccaalliinngg wwiitthh OOppeennGGLL
+
+ Another general solution to the scaling problem is to use the texture
+ scaling found in all 3D hardware. This ability is already exposed
+ through OpenGL and can be exploited by clients without X server
+ modification (i.e., other than the ability to support OpenGL). An
+ application using OpenGL would transmit the non-scaled image to the X
+ server as a texture, and would then display a single non-transformed
+ rect using that texture. This also works around the single overlay
+ problem with the X Video Extension as well as the need to implement
+ additional scaled primitive extensions.
+
+ The downside is that most OpenGL implementations require power of 2
+ texture sizes and this can be very wasteful of memory if, for example,
+ the application needs to scale a 1025x1025 image, which would require
+ a 2048x2048 texture area (even a 640x480 image would require a
+ 1024x512 texture). Another downside is that some OpenGL
+ implementations have a limited about of texture memory and cannot
+ handle textures that are very large. For example, they might limit
+ the texture size to 1024x1024.
+
+ 33..22.. AApppplliiccaattiioonn--ttrraannssppaarreenntt SSccaalliinngg ffoorr DDMMXX
+
+ 33..22..11.. BBaacckk--eenndd SSccaalliinngg WWiitthhoouutt DDiissccoonnnneecctt//RReeccoonnnneecctt
+
+ VNC does scaling on the client side (in the vncviewer application).
+ Implementing a similar solution for DMX would require support in the
+ back-end X servers and, therefore, is not a general solution.
+
+ XFree86 already implements some support for "scaling" that could be
+ used with DMX: if, in the XF86Config file, multiple Modes are listed
+ in the Display Subsection of the Screen Section, then pressing Ctrl-
+ Alt-Plus and Ctrl-Alt-Minus can be used to iterate through the listed
+ modes. The display dimensions will change to the dimensions in the
+ Modes line, but the logical dimensions of the X server (i.e., the
+ dimensions that Xdmx knows about) will not change.
+
+ Further, the dimensions of the XFree86 display are under software
+ control (via the XFree86-VidModeExtension), so the Xdmx server could
+ change the screen dimensions on a per-display basis, thereby scaling
+ the information on part of that display.
+
+ However, this scaling appears to have limited use. For example,
+ assume a 4 by 4 display wall consisting of 16 1280x1024 displays. If
+ all of the back-end servers were simultaneously configured to display
+ 640x480, the left hand corner of each display would be magnified, but
+ the composite result would be unreadable. Magnifying one display at a
+ time could be usable, but could have limited utility, since the result
+ would still be no larger than a single display.
+
+
+ 33..22..22.. BBaacckk--eenndd SSccaalliinngg WWiitthh DDiissccoonnnneecctt//RReeccoonnnneecctt
+
+ Disconnect and reconnect features are not currently supported in DMX,
+ but are scheduled to be implemented in the future. These features,
+ combined with the XFree86-VidModeExtension Extension, would allow an
+ application to do the following:
+
+ +o Disconnect a specific back-end server (via the DMX Extension),
+
+ +o reconfigure the XFree86 back-end server resolution, and
+
+ +o reconnect the back-end server to DMX -- at a new origin with the
+ new screen resolution.
+
+ For example, consider a display wall consisting of 16 1280x1024
+ displays with a total resolution of 5120x4096. All of the screens
+ could be disconnected, repositioned, and reconnected each at a
+ resolution of 640x480. The total resolution of the display wall would
+ be 2560x1920, allowing a view of a selected area approximately one-
+ fourth of the size of the DMX display. This change would be
+ completely application independent (except, perhaps, for a DMX-aware
+ window manager). When work at the increased resolution was completed,
+ the back-end servers could be disconnected, reconfigured, and
+ reconnected for the original 5120x4096 view.
+
+ Support for this type of scaling can be implemented in a DMX-aware X11
+ client assuming the DMX server support arbitrary disconnect and
+ reconnect semantics. Because this application cannot be written
+ before disconnect/reconnect is implemented, this solution will not be
+ discussed further in this paper.
+
+ 33..22..33.. SSeerrvveerr--ssiiddee SSccaalliinngg
+
+ In earlier versions of DMX, a frame buffer was maintained on the
+ server side, and XPutImage was used to move the information from the
+ server to the client (similar to some early VNC implementations). The
+ use of a server-side frame buffer would allow the server to do
+ scaling, but is not a recommended solution because of overall
+ performance issues and server-side memory issues (i.e., the frame
+ buffer would be very large for large display walls).
+
+ Exploration of this path is not recommended.
+
+ 33..33.. XXCCrreeaatteeSSccaalleeddWWiinnddooww AAPPII
+
+ The implementation of X Video Extension in DMX, and the use of
+ XvPutImage by applications requiring scaling requires significant
+ changes in DMX Further, XvPutImage is, essentially a scaled blit, and
+ it is only useful for applications which are already using (or can be
+ modified to use) XPutImage. Therefore, a more general API will be
+ discussed as another possibility.
+
+ X applications typically create windows with the XCreateWindow call.
+ A new extension could provide an XCreateScaledWindow call that could
+ be used in place of the XCreateWindow call and be otherwise
+ transparent to the application. This would allow applications, even
+ those that do not depend on XPutImage, to take advantage of window
+ scaling. In this section we describe how the call would work, what
+ transparency it provides, and how to solve the potential problems that
+ transparency creates.
+
+ 33..33..11.. XXCCrreeaatteeWWiinnddooww
+
+ The XCreateWindow call takes width and height as parameters. An
+ XCreateScaledWindow call could take all the same parameters, with the
+ addition of a scaling factor.
+ 33..33..22.. XXSSeettWWiinnddoowwAAttttrriibbuutteess
+
+ An X11 window has several attributes that would have to be scaled:
+
+ +o Background and border pixmaps
+
+ +o Border width
+
+ +o Cursor
+
+ 33..33..33.. XXGGeettWWiinnddoowwAAttttrriibbuutteess,, XXGGeettGGeeoommeettrryy
+
+ For transparency, calls that query the window attributes should return
+ unscaled information. This suggests that all unscaled pixmaps and
+ window attributes should be cached.
+
+ Unfortunately, a window manager requires the scaled geometry to
+ properly decorate the window. The X server can probably determine
+ which client is acting as the window manager (e.g., because that
+ client will select events that are used exclusively by the window
+ manager). However, other Scaled Window Extension aware clients may
+ also need to determine the scaled geometry. Therefore, at least two
+ additional extension calls should be implemented:
+ XGetScaledWindowAttributes and XGetScaledGeometry.
+
+ 33..33..44.. PPooppuupp aanndd CChhiilldd wwiinnddooww ppoossiittiioonnss
+
+ Some applications may position popup and child windows based on an
+ unscaled notion of the main window geometry. In this case, additional
+ modifications to the client would be required.
+
+ 33..33..55.. EEvveennttss
+
+ Most events (e.g., for mouse motion) return information about the
+ coordinates at which the even occurred. These coordinates would have
+ to be modified so that unscaled values were presented to the client.
+
+ 33..33..66.. IImmpplleemmeennttaattiioonn
+
+ There are many implementation issues, some of which are similar to the
+ issues involved in implementing the X Video Extension for DMX. The
+ window contents must be scaled, either by performing all operations to
+ a frame buffer and then writing the image to the display (perhaps
+ using hardware scaling support), or by modifying all of the various
+ drawing operations to perform scaling. Because of the complexity
+ involved, the frame buffer option is recommended.
+
+ 44.. CCoonncclluussiioonn aanndd RReeccoommmmeennddaattiioonnss
+
+ We recommend a three phase implementation strategy, based on how an
+ application could be written to take advantage of scaling:
+
+ 1.
+
+ The XCopyAreaScaled extension should be implemented, since this is
+ the ideal solution for applications like VNC, and since making use
+ of this extension will require minimal changes to applications that
+ already use XPutImage or XCopyArea.
+
+ The initial implementation work would include the design of the X
+ protocol extension, writing this up in the usual format for
+ extension documentation, implementation of the protocol transport
+ pieces in XFree86, implementation of a software fall-back in
+ XFree86 and DMX, one example hardware implementation for XFree86,
+ and implementation of support for this extension in DMX.
+
+ We suggest implementing the extension first on the ATI Radeon
+ cards. However, since these cards do not provide a 2D scaled blit
+ primitive, the implementation would have to make use of the 3D
+ texture engine to emulate a scaled blit. This is recommended,
+ since other modern graphics cards also do not provide a simple 2D
+ scaled blit operation and an example of the more difficult
+ implementation pathway would be helpful to others.
+
+ 2.
+
+ Until XCopyAreaScaled is widely supported, applications that
+ require scaling will have to fall back to another scaling method.
+ We suggest OpenGL as the first fall-back method because it is
+ widely available and supported by DMX.
+
+ A project centered around OpenGL-based scaling would implement this
+ scaling in VNC as an example. This work would include re-writing
+ the vncviewer rendering engine to cache a master copy of the
+ desktop image for all operations.
+
+ 3.
+
+ Since OpenGL is not implemented everywhere, and may not provide
+ hardware-assisted performance in every implementation, an
+ application that requires scaling should also fall back to using
+ the X Video Extension.
+
+ This project would add support for the X Video Extension to DMX and
+ would add support to VNC to take advantage of this extension
+ without introducing artifacts. This would require modifying the
+ vncviewer rendering engine to cache a master copy of the desktop
+ image for all operations. This project should also add support for
+ the RGB format to at least one XFree86 driver (e.g., ATI Radeon).
+
+ The X Video Extension is one of the few popular extensions that DMX
+ does not support. We recommend implementing the X Video Extension
+ even if scaling is the specific goal of that work.
+
+ We do nnoott recommend implementation of the XCreateScaledWindow
+ extension because of the complexity involved. We do nnoott recommend
+ implementation of the XPutImageScaled extension because it requires
+ the same amount of work as the XCopyAreaScaled extension, but provides
+ less functionality. Further, server-side scaling with a large frame
+ buffer is nnoott recommended because of the performance implications.
+
+ The back-end scaling, especially with disconnect/reconnect support
+ should be explored in the future after disconnect/reconnect is
+ implemented, but not at the present time.
+
+
+
diff --git a/hw/dmx/doc/scaled.txt b/hw/dmx/doc/scaled.txt
deleted file mode 100644
index d30105d..0000000
--- a/hw/dmx/doc/scaled.txt
+++ /dev/null
@@ -1,579 +0,0 @@
- Scaled Window Support in DMX
- Rickard E. Faith and Kevin E. Martin
- 15 October 2003 (created 19 September 2003)
-
- This document investigates the possibility of adding scaled window
- support to the DMX X server, thereby allowing a window or some
- selected part of the logical DMX area to be displayed using a scaling
- factor. For example, this might allow the contents of a window to be
- magnified for easier viewing. In particular, scaling for the VNC
- client is explored. _C_o_p_y_r_i_g_h_t _2_0_0_3 _b_y _R_e_d _H_a_t_, _I_n_c_._, _R_a_l_e_i_g_h_, _N_o_r_t_h
- _C_a_r_o_l_i_n_a
-
- ______________________________________________________________________
-
- Table of Contents
-
-
- 1. Introduction
- 1.1 DMX
- 1.2 Problem Statement
- 1.3 Task
-
- 2. Previous Work
- 2.1 VNC
- 2.1.1 Scaling under VNC
- 2.2 The X Video Extension
-
- 3. Possible Solutions
- 3.1 VNC-like Scaling
- 3.1.1 Software Scaling
- 3.1.2 Scaling with the X Video Extension
- 3.1.2.1 Implementing the X Video Extension for DMX
- 3.1.2.2 Supporting RGB formats for the X Video Extension
- 3.1.3 Scaling with an XPutImageScaled Extension
- 3.1.4 Scaling with an XCopyAreaScaled Extension
- 3.1.5 Scaling with OpenGL
- 3.2 Application-transparent Scaling for DMX
- 3.2.1 Back-end Scaling Without Disconnect/Reconnect
- 3.2.2 Back-end Scaling With Disconnect/Reconnect
- 3.2.3 Server-side Scaling
- 3.3 XCreateScaledWindow API
- 3.3.1 XCreateWindow
- 3.3.2 XSetWindowAttributes
- 3.3.3 XGetWindowAttributes, XGetGeometry
- 3.3.4 Popup and Child window positions
- 3.3.5 Events
- 3.3.6 Implementation
-
- 4. Conclusion and Recommendations
-
-
- ______________________________________________________________________
-
- 11.. IInnttrroodduuccttiioonn
-
- 11..11.. DDMMXX
-
- The DMX X server (Xdmx) is a proxy server that is designed to allow X
- servers on multiple machines to be combined into a single multi-headed
- X server. Combined with Xinerama, these heads can appear as a single
- very high-resolution screen. Typical applications include the
- creation of a video wall with 16 1280x1024 displays arranged in a
- rectangle, for a total resolution of of 5120x4096.
-
-
-
- 11..22.. PPrroobblleemm SSttaatteemmeenntt
-
- Applications displayed on a physically large video wall that provides
- high pixel-resolution may be difficult to see, especially if the
- application is designed for use on a typical desktop computer with a
- relatively small display located close to the human operator. The
- goal of this paper is to describe and discuss solutions to this
- problem.
-
- The original driving problem for this work is to provide scaling for
- the vncviewer application when displayed using DMX (VNC scaling is
- currently available only with the Windows client, and there is no plan
- to extend that capability to other clients). While this specific
- problem will be addressed in this paper, the general solution space
- will also be explored, since this may lead to a good solution not only
- for vncviewer but also for other applications.
-
- 11..33.. TTaasskk
-
- For reference, here is the original description of the task this paper
- addresses:
-
- +o Scaled window support (for VNC)
-
- +o Investigate possibility of implementing a "scaled window"
- extension:
-
- +o Add XCreateScaledWindow call that could be used in place of
- XCreateWindow
-
- +o All primitives drawn to scaled window would be scaled by
- appropriate (integral?) scaling factor
-
- +o Alternate approach: special case VNC support
-
- 22.. PPrreevviioouuss WWoorrkk
-
- This section reviews relevant previous work.
-
- 22..11.. VVNNCC
-
- 22..11..11.. SSccaalliinngg uunnddeerr VVNNCC
-
- When using the vncviewer program for Windows, it is possible to
- specify a scaling factor (as numerator and denominator). When scaling
- is in effect, the viewer software uses StretchBlt (instead of BitBlt)
- to display the pixels for the user. When this call is made, the
- viewer already has received all of the pixel information (at full
- unscaled resolution).
-
- The scaling in VNC is primitive. It does not conserve bandwidth, it
- does not treat textual information differently (i.e., by using a
- suitably scaled font), and it does not provide any anti-aliasing other
- than that provided by the underlying (Windows-only) system library.
-
- 22..22.. TThhee XX VViiddeeoo EExxtteennssiioonn
-
- The X Video Extension is a widely-available extension to the X11
- protocol that provides support for streaming video. Integral to this
- support is the ability to arbitrarily scale the output. In version
- 2.2 of the X Video specification, support for scaled still images was
- provided, using both shared memory and traditional transport. The API
- for this support uses calls that are quite similar to XCreateWindow,
- XPutImage, and XShmPutImage. Currently, most of the drivers
- implemented in XFree86 only support data in various YUV formats.
- However, several modern video adaptors support RGB as well.
- Note, though, that the target output for this scaling is an overlay
- plane -- so X Video provides functionality that is fundamentally
- different from that provided by the Windows StrechBlt call.
-
- 33.. PPoossssiibbllee SSoolluuttiioonnss
-
- This section briefly discusses possible solutions, including major
- advantages and disadvantages from both the implementation and the end-
- user programmer standpoint.
-
- 33..11.. VVNNCC--lliikkee SSccaalliinngg
-
- 33..11..11.. SSooffttwwaarree SSccaalliinngg
-
- The vncviewer application could be modified to provide software
- scaling. This is not a general solution, but it does solve one of the
- goals of this work.
-
- A prototype of this solution was implemented and a patch against
- vnc-3.3.7-unixsrc is available in the dmx/external directory. Because
- of limited time available for this work, all of the edge cases were
- not considered and the solution works well mainly for integer scaling.
-
- Currently, vncviewer writes to the X display with XPutImage,
- XCopyArea, and XFillRectangle. All instances of these calls have to
- be aware of scaling and must round correctly. In the prototype
- solution, rounding is incorrect and can cause artifacts.
-
- A better solution would be to cache all updates to the desktop image
- in vncviewer and only send the damaged area to the X display with
- XPutImage. This would allow the damaged area to be computed so that
- rounding errors do not create artifacts. This method is probably
- similar to what is used in the Window client. (The whole VNC suite is
- being re-written in C++ and the forthcoming version 4 has not been
- evaluated.)
-
- 33..11..22.. SSccaalliinngg wwiitthh tthhee XX VViiddeeoo EExxtteennssiioonn
-
- The scaling in the Windows vncviewer application makes use of a scaled
- blit that is supplied by the underlying system library. Several video
- cards currently provide support for a scaled blit, and some X servers
- (including XFree86) expose this capability to applications via the
- XvPutImage interface of the X Video Extension. The capability exposed
- by XvPutImage results in the scaled image being drawn to an overlay
- plane. Most video cards also provide support for a scaled blit into
- the normal output planes, but this is not exposed via XvPutImage.
-
- The vncviewer program could be modified to use the X Video Extension
- to provide scaling under X11 that is similar to the scaling currently
- provided under Windows. Unfortunately, Xdmx does not currently export
- the X Video Extension, so this would not provide an immediate solution
- usable with DMX.
-
- A very early-stage proof-of-concept prototype was implemented and a
- preliminary patch against vnc-3.3.7-unixsrc is available in the
- dmx/external directory. This prototype was implemented to better
- understand the problems that must be solved to make this solution
- viable:
-
- +o As noted under the software scaling section above, vncviewer writes
- to the X display with several different calls. These calls write
- to the normal output planes and are compatible with XvPutImage,
- which writes to an overlay plane. To eliminate artifacts caused by
- this problem, vncviewer should be modified so that a cached copy of
- the desktop is available, either as a client-side image or a
- server-side off-screen pixmap, so that XvPutImage would be the only
- method for writing to the X display.
-
- +o
-
- Although several modern graphics adaptors support hardware scaling
- using an RGB format (e.g., ATI Radeon, nVidia, etc.), XFree86
- drivers typically only implement YUV formats. YUV generally
- compress the pixel information in some way. For example, two
- commonly implemented formats, YUY2 and UYVY provide intensity
- information for every RGB pixel, but only provide chroma and
- luminance information for pairs of horizontal pixels. Since VNC
- uses pixel-resolution for communicating updates on the wire,
- additional artifacts are introduced (because there may not be
- enough information from the wire to update a pair of pixels).
-
- Further, the well-known problem with YUV encoding is even more
- evident when the image is a desktop instead of a movie. For
- example, consider a 1-pixel-wide vertical window border. If the
- border changes in color but not intensity (e.g., because a window
- manager uses color to indicate focus), there may or may not be a
- change in the YUY2 image, depending on the algorithm used for RGB
- to YUV conversion and on how the border pixel is ordered in the
- pair of pixels used by the algorithm.
-
- Many of these artifacts could be eliminated if vncviewer cached a
- complete RGB image of the desktop, and only did the conversion to
- YUV for properly aligned areas of damage. The remaining artifacts
- could be eliminated if an RGB format was used with X Video (which
- may require the extension of existing XFree86 drivers to support
- RGB).
-
- +o Most modern video cards support exactly one overlay plane that is
- suitable for use with X Video. Therefore, only one application can
- use X Video at any given time. This is a severe limitation in a
- desktop environment.
-
- 33..11..22..11.. IImmpplleemmeennttiinngg tthhee XX VViiddeeoo EExxtteennssiioonn ffoorr DDMMXX
-
- The user-level API for X Video is fairly simple, but the underlying
- support required for the full specification is large. However, since
- the API provides a method to query supported capabilities, a usable
- subset of X Video can be implemented that would support XvPutImage and
- little else. This would require support for the following:
-
- +o X Video Extension API calls, including the following:
-
- +o XvQueryExtension
-
- +o XvQueryAdaptors
-
- +o XvQueryPortAttributes
-
- +o XvFreeAdaptorInfo
-
- +o XvListImageFormats
-
- +o XvGrabPort
-
- +o XvCreateImage
-
- +o XvPutImage
-
- +o XvShmCreateImage
-
- +o XvShmPutImage
-
- +o Support for querying back-end X Video Extension capabilities.
-
- +o Support for sending the image to the back-ends. Because X Video
- requires sending full images, there may be a trade-off between
- bandwidth limitations and additional complexity to divide the image
- up such that is scales properly.
-
- +o Possible support for a software fall-back. For example, if all of
- the back-ends do not support the X Video Extension, software
- scaling can be implemented such that the image is sent to the back-
- end with XPutImage. This pathway would have poor performance.
-
- 33..11..22..22.. SSuuppppoorrttiinngg RRGGBB ffoorrmmaattss ffoorr tthhee XX VViiddeeoo EExxtteennssiioonn
-
- Assuming an XFree86 driver already supports the X Video Extension, and
- assuming the target hardware supports an RGB format, then adding
- support for that format is relatively simple and straightforward.
-
- 33..11..33.. SSccaalliinngg wwiitthh aann XXPPuuttIImmaaggeeSSccaalleedd EExxtteennssiioonn
-
- Instead of (or in addition to) implementing the X Video Extension in
- DMX, one obvious solution would be to implement a new extension that
- provides access to hardware-assisted scaled blits, similar to the
- StretchBlt call available under Windows. This call would scale RGB
- images and would not use the overlay plane (unlike the X Video
- Extension).
-
- This approach has many of the same advantages and disadvantages as the
- XCopyAreaScaled Extension, discussed in the next section. Discussion
- of XPutImageScaled is deferred in favor of XCopyAreaScaled for the
- following reasons:
-
- +o XPutImageScaled can be emulated with XCopyAreaScaled by first using
- XPutImage to copy the image to an off-screen pixmap, and then
- calling XCopyAreaScaled between that off-screen pixmap and the
- target drawable.
-
- +o Since XCopyAreaScaled would copy between two areas of on-screen or
- off-screen memory, it has additional uses and can be viewed as
- efficiently providing a superset of XPutImageScaled functionality.
-
- 33..11..44.. SSccaalliinngg wwiitthh aann XXCCooppyyAArreeaaSSccaalleedd EExxtteennssiioonn
-
- As noted in the previous section, because XCopyAreaScaled provides a
- superset of the functionality provided by XPutImageScaled, we will
- consider this extension instead.
-
- First, XCopyAreaScaled would provide for RGB scaling between pixmaps
- (i.e., on-screen or off-screen areas of memory that reside on the
- video card). Unlike the X Video Extension, which writes into an
- overlay plane, XCopyAreaScaled would write into the non-overlay areas
- of the screen. Key points to consider are as follows:
-
- +o Because different planes are involved, the two scaling operations
- are usually implemented in hardware differently, so an
- XCopyAreaScaled extension could be added in a manner that would
- neither conflict with nor interact with the X Video extension in
- any way.
-
- +o The XCopyAreaScaled extension provides new functionality that the X
- Video Extension does not provide. Based on anecdotal feedback, we
- believe that many people outside the DMX and VNC communities would
- be excited about this extension.
-
- +o The main drawback to this extension is that it is new and needs to
- be implemented at the driver level in XFree86 for each video card
- to be supported. At the present time, it is more likely that the X
- Video Extension will be implemented for a particular piece hardware
- because the X Video extension has multimedia uses. However, over
- time, we would expect the XCopyAreaScaled extension to be
- implemented along with the X Video extension, especially if it
- becomes popular.
-
- +o Another drawback is that not all modern cards provide support for a
- simple scaled blit operation. However, these cards usually do
- provide a 3D pipeline which could be used to provide this
- functionality in a manner that is transparent to the client
- application that is using the XCopyAreaScaled extension. However,
- this implementation pathway would make this extension somewhat more
- difficult to implement on certain cards.
-
- 33..11..55.. SSccaalliinngg wwiitthh OOppeennGGLL
-
- Another general solution to the scaling problem is to use the texture
- scaling found in all 3D hardware. This ability is already exposed
- through OpenGL and can be exploited by clients without X server
- modification (i.e., other than the ability to support OpenGL). An
- application using OpenGL would transmit the non-scaled image to the X
- server as a texture, and would then display a single non-transformed
- rect using that texture. This also works around the single overlay
- problem with the X Video Extension as well as the need to implement
- additional scaled primitive extensions.
-
- The downside is that most OpenGL implementations require power of 2
- texture sizes and this can be very wasteful of memory if, for example,
- the application needs to scale a 1025x1025 image, which would require
- a 2048x2048 texture area (even a 640x480 image would require a
- 1024x512 texture). Another downside is that some OpenGL
- implementations have a limited about of texture memory and cannot
- handle textures that are very large. For example, they might limit
- the texture size to 1024x1024.
-
- 33..22.. AApppplliiccaattiioonn--ttrraannssppaarreenntt SSccaalliinngg ffoorr DDMMXX
-
- 33..22..11.. BBaacckk--eenndd SSccaalliinngg WWiitthhoouutt DDiissccoonnnneecctt//RReeccoonnnneecctt
-
- VNC does scaling on the client side (in the vncviewer application).
- Implementing a similar solution for DMX would require support in the
- back-end X servers and, therefore, is not a general solution.
-
- XFree86 already implements some support for "scaling" that could be
- used with DMX: if, in the XF86Config file, multiple Modes are listed
- in the Display Subsection of the Screen Section, then pressing Ctrl-
- Alt-Plus and Ctrl-Alt-Minus can be used to iterate through the listed
- modes. The display dimensions will change to the dimensions in the
- Modes line, but the logical dimensions of the X server (i.e., the
- dimensions that Xdmx knows about) will not change.
-
- Further, the dimensions of the XFree86 display are under software
- control (via the XFree86-VidModeExtension), so the Xdmx server could
- change the screen dimensions on a per-display basis, thereby scaling
- the information on part of that display.
-
- However, this scaling appears to have limited use. For example,
- assume a 4 by 4 display wall consisting of 16 1280x1024 displays. If
- all of the back-end servers were simultaneously configured to display
- 640x480, the left hand corner of each display would be magnified, but
- the composite result would be unreadable. Magnifying one display at a
- time could be usable, but could have limited utility, since the result
- would still be no larger than a single display.
-
-
- 33..22..22.. BBaacckk--eenndd SSccaalliinngg WWiitthh DDiissccoonnnneecctt//RReeccoonnnneecctt
-
- Disconnect and reconnect features are not currently supported in DMX,
- but are scheduled to be implemented in the future. These features,
- combined with the XFree86-VidModeExtension Extension, would allow an
- application to do the following:
-
- +o Disconnect a specific back-end server (via the DMX Extension),
-
- +o reconfigure the XFree86 back-end server resolution, and
-
- +o reconnect the back-end server to DMX -- at a new origin with the
- new screen resolution.
-
- For example, consider a display wall consisting of 16 1280x1024
- displays with a total resolution of 5120x4096. All of the screens
- could be disconnected, repositioned, and reconnected each at a
- resolution of 640x480. The total resolution of the display wall would
- be 2560x1920, allowing a view of a selected area approximately one-
- fourth of the size of the DMX display. This change would be
- completely application independent (except, perhaps, for a DMX-aware
- window manager). When work at the increased resolution was completed,
- the back-end servers could be disconnected, reconfigured, and
- reconnected for the original 5120x4096 view.
-
- Support for this type of scaling can be implemented in a DMX-aware X11
- client assuming the DMX server support arbitrary disconnect and
- reconnect semantics. Because this application cannot be written
- before disconnect/reconnect is implemented, this solution will not be
- discussed further in this paper.
-
- 33..22..33.. SSeerrvveerr--ssiiddee SSccaalliinngg
-
- In earlier versions of DMX, a frame buffer was maintained on the
- server side, and XPutImage was used to move the information from the
- server to the client (similar to some early VNC implementations). The
- use of a server-side frame buffer would allow the server to do
- scaling, but is not a recommended solution because of overall
- performance issues and server-side memory issues (i.e., the frame
- buffer would be very large for large display walls).
-
- Exploration of this path is not recommended.
-
- 33..33.. XXCCrreeaatteeSSccaalleeddWWiinnddooww AAPPII
-
- The implementation of X Video Extension in DMX, and the use of
- XvPutImage by applications requiring scaling requires significant
- changes in DMX Further, XvPutImage is, essentially a scaled blit, and
- it is only useful for applications which are already using (or can be
- modified to use) XPutImage. Therefore, a more general API will be
- discussed as another possibility.
-
- X applications typically create windows with the XCreateWindow call.
- A new extension could provide an XCreateScaledWindow call that could
- be used in place of the XCreateWindow call and be otherwise
- transparent to the application. This would allow applications, even
- those that do not depend on XPutImage, to take advantage of window
- scaling. In this section we describe how the call would work, what
- transparency it provides, and how to solve the potential problems that
- transparency creates.
-
- 33..33..11.. XXCCrreeaatteeWWiinnddooww
-
- The XCreateWindow call takes width and height as parameters. An
- XCreateScaledWindow call could take all the same parameters, with the
- addition of a scaling factor.
- 33..33..22.. XXSSeettWWiinnddoowwAAttttrriibbuutteess
-
- An X11 window has several attributes that would have to be scaled:
-
- +o Background and border pixmaps
-
- +o Border width
-
- +o Cursor
-
- 33..33..33.. XXGGeettWWiinnddoowwAAttttrriibbuutteess,, XXGGeettGGeeoommeettrryy
-
- For transparency, calls that query the window attributes should return
- unscaled information. This suggests that all unscaled pixmaps and
- window attributes should be cached.
-
- Unfortunately, a window manager requires the scaled geometry to
- properly decorate the window. The X server can probably determine
- which client is acting as the window manager (e.g., because that
- client will select events that are used exclusively by the window
- manager). However, other Scaled Window Extension aware clients may
- also need to determine the scaled geometry. Therefore, at least two
- additional extension calls should be implemented:
- XGetScaledWindowAttributes and XGetScaledGeometry.
-
- 33..33..44.. PPooppuupp aanndd CChhiilldd wwiinnddooww ppoossiittiioonnss
-
- Some applications may position popup and child windows based on an
- unscaled notion of the main window geometry. In this case, additional
- modifications to the client would be required.
-
- 33..33..55.. EEvveennttss
-
- Most events (e.g., for mouse motion) return information about the
- coordinates at which the even occurred. These coordinates would have
- to be modified so that unscaled values were presented to the client.
-
- 33..33..66.. IImmpplleemmeennttaattiioonn
-
- There are many implementation issues, some of which are similar to the
- issues involved in implementing the X Video Extension for DMX. The
- window contents must be scaled, either by performing all operations to
- a frame buffer and then writing the image to the display (perhaps
- using hardware scaling support), or by modifying all of the various
- drawing operations to perform scaling. Because of the complexity
- involved, the frame buffer option is recommended.
-
- 44.. CCoonncclluussiioonn aanndd RReeccoommmmeennddaattiioonnss
-
- We recommend a three phase implementation strategy, based on how an
- application could be written to take advantage of scaling:
-
- 1.
-
- The XCopyAreaScaled extension should be implemented, since this is
- the ideal solution for applications like VNC, and since making use
- of this extension will require minimal changes to applications that
- already use XPutImage or XCopyArea.
-
- The initial implementation work would include the design of the X
- protocol extension, writing this up in the usual format for
- extension documentation, implementation of the protocol transport
- pieces in XFree86, implementation of a software fall-back in
- XFree86 and DMX, one example hardware implementation for XFree86,
- and implementation of support for this extension in DMX.
-
- We suggest implementing the extension first on the ATI Radeon
- cards. However, since these cards do not provide a 2D scaled blit
- primitive, the implementation would have to make use of the 3D
- texture engine to emulate a scaled blit. This is recommended,
- since other modern graphics cards also do not provide a simple 2D
- scaled blit operation and an example of the more difficult
- implementation pathway would be helpful to others.
-
- 2.
-
- Until XCopyAreaScaled is widely supported, applications that
- require scaling will have to fall back to another scaling method.
- We suggest OpenGL as the first fall-back method because it is
- widely available and supported by DMX.
-
- A project centered around OpenGL-based scaling would implement this
- scaling in VNC as an example. This work would include re-writing
- the vncviewer rendering engine to cache a master copy of the
- desktop image for all operations.
-
- 3.
-
- Since OpenGL is not implemented everywhere, and may not provide
- hardware-assisted performance in every implementation, an
- application that requires scaling should also fall back to using
- the X Video Extension.
-
- This project would add support for the X Video Extension to DMX and
- would add support to VNC to take advantage of this extension
- without introducing artifacts. This would require modifying the
- vncviewer rendering engine to cache a master copy of the desktop
- image for all operations. This project should also add support for
- the RGB format to at least one XFree86 driver (e.g., ATI Radeon).
-
- The X Video Extension is one of the few popular extensions that DMX
- does not support. We recommend implementing the X Video Extension
- even if scaling is the specific goal of that work.
-
- We do nnoott recommend implementation of the XCreateScaledWindow
- extension because of the complexity involved. We do nnoott recommend
- implementation of the XPutImageScaled extension because it requires
- the same amount of work as the XCopyAreaScaled extension, but provides
- less functionality. Further, server-side scaling with a large frame
- buffer is nnoott recommended because of the performance implications.
-
- The back-end scaling, especially with disconnect/reconnect support
- should be explored in the future after disconnect/reconnect is
- implemented, but not at the present time.
-
-
-
--
1.6.0.4
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