<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 TRANSITIONAL//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; CHARSET=UTF-8"> <META NAME="GENERATOR" CONTENT="GtkHTML/3.0.10"> </HEAD> <BODY> Hi Alexander, To answer your "eye-candy" question ... there isn't a whole lot out there that really demonstrates what is so great about the new Xorg. Its so new, that we really haven't tapped the new architecture yet. I'll begin with some background and to demonstrate whats so cool, and you can start thinking about how you really want your demonstration and what the goals of the demonstration should be. Most of the new changes in Xorg are related to the "pretty shadow" effect that everyone knows. However, its the underlying architecture that makes this possible that is really of importance. For the past .. oh .. 20 years maybe, the primary method of image composition has been the BITBLT, a method of more or less pasting an image onto the screen, usually as a square block of pixels. To that we add a bitmask so we can have non-square regions, but it still uses a bitblt, just with a few binary operations added to the equation. Pixels are on or off, or can have XOR or other bit operations done, but you are always dealing with regions of solid color on a single field of pixels. The new method breaks up the screen so that top-level windows are actually on their own "field" or "layer". This layer can have partially transparent portions. The data is stored off-screen, and the final display is generated using another helper application. Currently this is xcompmgr which renders the screen by using Porter/Duff image composition of the layers, which is used extensively in the film industry. In computer terms, we call this the "Alpha Channel". This is like the difference between a GIF and a PNG. A GIF can have a transparent area, but thats just a hole in the image. A PNG can have levels of transparency. By having this done by a seperate utility, you expose the power of the system to whatever uses you can devise for it, much like the original X made the Window Manager a seperate entity. Now the screen itself is rendered by a replaceable entity! What you can do with these alpha levels is the important part. Unlike a GIF that has to be pre-anti-aliased to its background to remove jaggies, a PNG can use its transparency layer for anti-aliasing so that it looks smooth against ANY background (great to do with Web pages!). This means that if you have round or curved Windows, by using the alpha channel they can be perfectly smooth. All your icons can have smooth edges with transparent drop-shadows, Windows can have drop-shadows against other windows. Imagine how this can be applied to remote display protocols like VNC, that can now be told exactly what has changed on the screen! Its the difference between the old blue-screen effect where you have a border and subtle jagged edges around what is being pasted over the video, and the new compositing where computer generated images are seamlessly integrated into live video (see link below). That right there might be a good place to start with your demonstration. Don't just show the new X - people have seen KDE drop-shadows and fake transparency effects for years. Its the underlying principle thats changed, and should be demonstrated in addition to the new X. A simple demonstration of what compositing is, can be done with a simple web page. Make a pretty image with lots of curves and such on a transparent layer in GIMP. Save it as a GIF and as a PNG. Display it on a web page with a background. You'll notice PNG's anti-aliasing works with any color. The GIF you have to paste the right color background under it and do the anti-aliasing on that color or image - a manual composite with Gimp that has to be redone for every background. The new X server does this on the fly (like the PNG). If you don't think anti-aliasing is important since you normally have square windows, think again about what happens under OS X when a window is iconified. During the animation, its not square at all, and it doesn't look jagged thanks to alpha-blending. How about mplayer/xine - some of those themes don't use square windows either! For an example of what I mean, go to <A HREF="http://coolrunningconcepts.com/cgi-bin/alpha-demo.cgi">http://coolrunningconcepts.com/cgi-bin/alpha-demo.cgi</A> Then select different background colors and patterns from the bar on the bottom (the jaggies are most noticeable with white). To make shadows and such fast, It's important to know what parts of the screen have to be redrawn, and therefore, which ones have to be recomposited. In the past, a rectangle list was used to divide up the screen and as a window was uncovered, the application was told to redraw that portion. Now, that portion might have a shadow over it, or the window above it might be transparent, so the Damage extension keeps track of what is damaged so it can be recomposited on the real display screen from the off-screen bitmaps where the application actually writes to. Because the application is no longer writing directly to the screen, the representation of the screen can be controlled by another application, such as xcompmgr. Imagine how this can be applied to remote display protocols like VNC, that can now be told exactly what has changed on the screen! I'm wondering if any of the anti-aliased font code makes use of semi-transparent pixel compositing. I believe so, as I don't see how else this could be done well, but I doubt its been integrated into the compositing system, and probably exists on its own. The compositing effects are limitless, from simple drop-shadows and transparencies, to more advanced things like the eye-candy when you iconify a window under OS X and it twists and slurps itself into its icon. The window can update during all this, so if you wanted non-selected windows to shrink to 75% of their size slowly and twist and curdle like cooking bacon, while working on another window, you could, while it was updating! Think of all the screen savers that take a snapshot of the screen! With Xorg 6.8, they can be rewritten to do these same effects without a snapshot, on a live screen, while it updates! If you have some programming skills, this might be the place to hack up a nice demo. There are some desktop eye-candy programs that make a spinning cube as you switch desktops, each desktop being a cube face ... but they annoyingly have to grab constant snapshots and the screens aren't live during the animation. Now they can be rewritten to do it right! 3D desktops with each window flipping and turning? No problem, now that the view of the desktop has been removed from the control of the application! Having a window display on the side of partially rotated cube is just a matter of making a replacement for xcompmgr that does some OpenGL. Here's an example of how one application has gone from emulating an OS X effect (with noticeable extra work and visual issues), to performing the identical function gracefully. Compare skippy and skippy-xd (XD for XDamage) here : <A HREF="http://thegraveyard.org/skippy.php">http://thegraveyard.org/skippy.php</A> This would be a great application to show for your demo! Also, demo Gnome, not KDE. People are used to the shadows under KDE, so demonstrate that its now possible for the system to do these effects without special help like the KDE hacks. Also, drag a Window around really fast. Then kill xcompmgr and do it again. Without xcompmgr, the system shows the limitations of the old X. You either bog the CPU with constant updating of small portions of the screen, or you get a trail of the old mess as each application waits its turn to update its window in bulk. With xcompmgr on, the off-screen displays and new features of X allow the window to be smoothly dragged over the screen at any speed, without a trail of waiting updates. For more info on Alpha Blending, check out this PDF <A HREF="ftp://ftp.alvyray.com/Acrobat/7_Alpha.pdf">ftp://ftp.alvyray.com/Acrobat/7_Alpha.pdf</A> Good luck with your demo, and sorry for the lengthy post. <A HREF="http://thegraveyard.org/skippy.php"></A> <TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%"> <TR> <TD> Thank You, Evan K. Langlois <A HREF="mailto:Evan@CoolRunningConcepts.com">Evan@CoolRunningConcepts.com</A> Cool Running Concepts. "Computing at the Speed of Thought" <A HREF="http://CoolRunningConcepts.com">http://CoolRunningConcepts.com</A> </TD> </TR> </TABLE> </BODY> </HTML>