Using composite in the desktop
The Composite extension allows redirecting window drawing operations to off-screen buffers. This allows the "composite manager" to do custom drawings of windows (like creating real transparency effects, etc). It also provides an ARGB visual that can be used by applications to draw using alpha-blending.
What could we do using composite?
The composite manager currently is able to do some translucency and shadow effects. It also does some fade-in/out effects in the windows. To get that, no change needs to be done in the applications. The composite manager does all the job. Besides that, we could create more interesting things, here some ideas:
- Alpha-blended window decoration. The window manager could have translucent borders and things like that. The mockup below is not something really impressive, but gives an idea of what can be done:
- Instant Help. I don't know how to call this, but the idea is to have help available for actions in the applications. Something like a what-is-this, but being easier for the user to access. By using transparency, we could add a small "?" near the active widget indicating there is help available on that. The help message could be shown in a semi-transparent window, or whatever we want it to look like. The mockup below shows an idea of the concept:
- "Composé" integrated in the composite manager. When the composite extension is enabled, we have the contents of all windows available for doing whatever we want. So why not doing a really usable "composé"? I mean, something that smoothly re-scale the windows and makes it possible for the user to choose the window he/she wants.
- Smoothness. Things like popups opening, window minimization/maximization could be smoother by showing the user all the steps since it press the minimize button until the window goes to the taskbar.
- Superkaramba. Superkaramba currently uses the background-copy method to create transparency. We could add support for ARGB visuals usage on it and make the transparency real. This is not that hard to be done, and the result would be really impressive.
What do we need to do to have composite working fine?
Acceleration
Composite will perform really bad if no acceleration or just XAA acceleration is available. Doing compositing operations by software is no way. XAA doesn't accelerate important operations we will be using for composite. When EXA acceleration is available, things get much better. I was running composite on a Radeon 9250 using the EXA acceleration, and things were working pretty well. So adding EXA acceleration to some drivers would be really good. See the ExaStatus page for more info.
Composite Manager x Window Manager
The composite manager and the window manager should be the same application. This is not really mandatory, but by merging the two it will be easier and faster to create composite effects.
Stability
Make the composite manager as stable and fast as possible. This is obvious, but it is a very important point. Also the drivers should be extensivelly tested to reach stability.