Ideas for X improvement.

Thu May 26 12:18:10 PDT 2011

I was not able to find any documentation on a VNC loadable module anywhere.
Is there a place where one can find out about this?

On Thu, May 26, 2011 at 7:34 AM, Pat Kane <pekane52 at gmail.com> wrote:

> I like VNC and have built both loadable module and DDX version.
>
> The main problem with the DDX version is that since VNC
> has a GPL  license I can not merge the code into my Xorg
> source tree.
>
> Pat
> ---
>
>
> On Wed, May 25, 2011 at 6:07 PM, David Jackson <djackson452 at gmail.com>
> wrote:
> >
> >
> > On Wed, May 25, 2011 at 4:36 PM, Glynn Clements <
> glynn at gclements.plus.com>
> > wrote:
> >>
> >> David Jackson wrote:
> >>
> >> > A display driver that contains a VNC server. The problem with x11vnc
> is
> >> > that
> >> > it is slow, very slow. XVnc server, which is a X server that contains
> a
> >> > VNC
> >> > server but has no hardware drivers, is much faster since the VNC
> server
> >> > is
> >> > built directly into the X server,
> >>
> >> What sample size does your analysis use? How many different hardware
> >> configurations, and how many different applications?
> >>
> >> x11vnc has the drawback that it's reading a framebuffer which is
> >> typically in video memory, so the data has to be read over the bus.
> >> The speed of this operation may vary significantly depending upon the
> >> hardware being used. It may also vary depending upon the amount of
> >> activity (i.e. if it has to wait for the outstanding rendering
> >> operations to complete before it's allowed to read the framebuffer).
> >>
> >> Xvnc has the advantage that the framebuffer is in system memory. But
> >> this is also a drawback, as it means that all rendering is performed
> >> in software. Try running an application which uses OpenGL to render
> >> detailed scenes; you might want to reconsider your assertion about
> >> Xvnc is fast.
> >>
> >> IOW, it's a case of "choose your poison". x11vnc has fast rendering
> >> but slow export, Xvnc has slow rendering but fast export. A similar
> >> tradeoff exists for X11 verus VNC for remote display.
> >>
> >> > however this does not allow one to export
> >> > their main X display which is also displayed directly to video
> hardware.
> >> > The
> >> > solution here is to include a driver in the X.org main server
> >> > distribution
> >> > for a VNC server that can be loaded into the X server. The VNC server
> >> > driver
> >> > should be able to be dynamically loaded while the server is running
> and
> >> > the
> >> > output of the server displayed simultaneously to VNC clients and to
> the
> >> > local video hardware. This can be controlled from provided command
> line
> >> > and
> >> > GUI utilities.
> >>
> >> Does the VNC driver read the framebuffer on the video card (which
> >> suffers from the same performance issues as x11vnc), or does it
> >> attempt to duplicate the framebuffer by emulating whatever video
> >> hardware is installed? If it's the latter, the application will be
> >> slowed to the speed of the VNC driver's software renderer (which will
> >> be extremely complex, as it will have to mimic every feature which is
> >> available in at least one hardware driver).
> >>
> >> > One of the very severe problems I have been having is that Xvnc does
> not
> >> > support Render extensions, and many applications no longer work
> without
> >> > the
> >> > Render extension. VNC driver with X.org therefore must support the
> >> > Render
> >> > extension and other ones.
> >>
> >> The main "other one" being OpenGL, for which a software implementation
> >> will be much, much slower than a modern GPU.
> >>
> >> > Dynamic runtime enabling and disabling, configuration and setup and
> >> > removal
> >> > of display output and input drivers while the server runs without
> server
> >> > restart. this allows for instance, the user to have the X server
> display
> >> > to
> >> > a new target while the server runs, or display to many different
> display
> >> > outputs at the same time This includes the VNC Server driver above,
> this
> >> > allows a person to easily swtich the VNC on and off from displaying to
> >> > certain outputs, such as they could turn off display to the local
> >> > monitor
> >> > and then turn it back on again, or turn on and off VNC display.
> >> >
> >> > Another feature that increases flexibility to the user would be to
> allow
> >> > the
> >> > user to direct display of a certain window or the entire root window
> and
> >> > display over an X client connection to another server, or any number
> of
> >> > other servers. This would also forward the windows children who would
> >> > also
> >> > be displayed on the remote server inside the parent window.
> >>
> >> To do this at the protocol level requires a completely new protocol
> >> and significant support from the toolkit. The X protocol exposes a
> >> significant amount of implementation detail to the client. Much of
> >> that information is required to remain constant for the lifetime of
> >> the client.
> >>
> >> E.g. if the client queries the list of OpenGL extensions, and starts
> >> using some of them, there's no mechanism by which to inform the client
> >> that an extension is suddenly unavailable, which would be required if
> >> you were to "redirect" the window to a different server with different
> >> hardware.
> >>
> >> Even if such a mechanism existed, it's debatable how many applications
> >> would support it. Reconstructing the current server-side state from
> >> scratch is a lot of work, and toolkits can't always help (e.g. they
> >> won't help reconstruct the server-side OpenGL state, as the toolkit
> >> doesn't get involved in the rendering process).
> >>
> >> > Many users, including myself, want to have many X servers running at
> the
> >> > same time and then at run time be able to change to where these
> servers
> >> > are
> >> > being displayed, and as well when an app is started, to which server
> it
> >> > is
> >> > displayed with the -display option.
> >>
> >> AFAICT, there are only two feasible approaches to window "mobility":
> >>
> >> 1. VNC-like framebuffer sharing. The application connects to a
> >> specific X server which performs all rendering. You have the option to
> >> forward rendered images to other systems for physical display.
> >>
> >> 2. Use GUI toolkits which offer an abstract, high-level interface to
> >> the client. The toolkit has the ability reconstruct and clone windows
> >> at will.
> >>
> >> --
> >> Glynn Clements <glynn at gclements.plus.com>
> >> _______________________________________________
> >> xorg at lists.freedesktop.org: X.Org support
> >> Archives: http://lists.freedesktop.org/archives/xorg
> >> Info: http://lists.freedesktop.org/mailman/listinfo/xorg
> >> Your subscription address: djackson452 at gmail.com
> >
> >
> > x11vnc is noticeably slower. I think the really annoying thing that makes
> it
> > hard to use is that there is a longer delay when typing for characters to
> > display on the screen than there is with Xvnc. I can notice this. When
> you
> > are typing characters do display much more quickly to the screen on Xvnc.
> > That is a big issue, because, it is really hard to type when you have a
> long
> > delay of characters appearing when you type them.Perhaps this is due the
> > polling of the framebuffer.
> >
> > The VNC driver could  do its own rendering, get the graphics commands
> from
> > the application directly. Yes, you are correct that is slow for many
> complex
> > operations. You are correct, the other alternative is to grab the
> > framebuffer. You are correct it might be faster for those complex
> graphics.
> > Grabbing the framebuffer inside the X server and feeding it out to VNC
> > clients via a VNC server in the X server, might save a little bit of time
> by
> > avoiding having to be sent over a socket to another process, but i do not
> > know if that is true. It may be it might do all that being interrupted
> fewer
> > or no times, where with x11vnc you are gauranteed a task switch and some
> > time for x11vnc to get the CPU. I guess x11vnc asks for the framebuffer
> over
> > an X connection, then wait for the X server to get the CPU to process the
> > request, then wait again for x11vnc to get CPU and the data to be sent to
> > VNC clients. if we have a framebuffer based VNC driver inside the X
> server,
> > it may allow for tighter synchronisation and less delay. I cannot say how
> > significant it would be.
> >
> > The other issue mentioned, about the window forward feature. You are
> > correct. I have been thinking about these issues. It would be best for it
> to
> > be invisible to clients. Ive been thinking about these problems.
> >
> > I am know C, however I know little about X internals or X protocol. Is
> there
> > a good source of documentation that would give a person a full
> introduction
> > and overview of how the X server works,including how it all fits
> together,
> > and a tour of the system and documentation of the internals such as
> > functions, variables etc? Basically everything need for a person who only
> > knows C to learn all about how the X server works?
> >
> >
> >
> > _______________________________________________
> > xorg at lists.freedesktop.org: X.Org support
> > Archives: http://lists.freedesktop.org/archives/xorg
> > Info: http://lists.freedesktop.org/mailman/listinfo/xorg
> > Your subscription address: pekane52 at gmail.com
> >
>
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