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Compiz and Fedora



Hi,

I read through the entire "Enabling Compiz by default" thread and
decided to send out a braindump/status/roadmap type of writeup, to
explain what we're doing in this area and where we'd like to go:

1) We are working towards being able to enable a compositor by default.

        Redirected direct rendering, Xv, Java problems, these are
        problems in the drivers and X server and affects all
        compositors.  To get this done, we need to land a big chunk of
        code in the kernel (the DRM memory manager), we need to update
        the X server, the 2D drivers and the 3D drivers to take
        advantage of the new memory manager.  We need to fix Xv.
        Hopefully the OpenGL support will broaden to support more
        chipsets (nouveaou, avivo). Getting all this to a shippable
        state may take years, and in the mean time, the composited
        desktop, whether it's compiz, kwin4 or something else will only
        be an opt-in tech demo.
        
2) Once we get there, the default compositor will be compiz.

        Some people can't get over on the wobbly windows and spinning
        cube, and claim it's over the top or apparently get nauseous.
        At the core, compiz is just a very efficient OpenGL redraw loop
        with a flexible plugin architecture.  Compiz allows burning
        windows and spinning cubes, but we ship it in a very toned down
        default configuration that looks a lot like good old metacity.
        Consider xeyes; like wobbly windows, it's a neat tech demo and
        shows off the flexibility of X, but just because nobody runs
        xeyes for more that 2 minutes at a time that doesn't mean that X
        (or shaped windows) isn't useful.
        
        A valid point about compiz is that it is not yet a great window
        manager.  Metacity has a few years of head start there, but that
        doesn't mean that we can't fix compiz or that it'll be
        duplicated effort.  For now, our efforts have gone towards
        fixing the big underlying shortcomings in the X and OpenGL
        stack, which has left compiz with a set of minor (but certainly
        annoying) windows manager bugs.
        
        Other spins (Fedora KDE or Fedora XFCE) can set up different
        default compositing managers, and they will of course benefit
        from the infrastructure work mentioned in 1).

3) Metacity as a compositing manager.

        We tried it and decided that the metacity code base was not a
        welcoming place for a compositor.  When we put down the work in
        metacity, the conclusion was to leave this very stable and well
        tested code base alone instead of injecting an OpenGL based
        compositor.  The flip side of this decision is that we can now
        do a clean break in compiz and assume throughout the code that
        we're an OpenGL based combined compositing and window manager.
        
4) Compiz configuration tools

        desktop-effects is close to what we should ship by default,
        perhaps we want to fold it into the new
        gnome-appearance-properties capplet as a new tab.  At the same
        time, we want to allow installation of other compiz
        configuration managers for people who like the tweak-ui kind-of
        tools.

4) Power consumption and other hand-wavey fud arguments.

        Clearly running a 3D screen saver at the full frame rate is
        going to burn more battery than the blank screen saver, but
        that's not really relevant here.  When idling, compiz and
        metacity use exactly the same amount of power.  There are no
        code paths anywhere in the stack that "turn on 3d powerplanes".
        My bet is that it's more power consuming to wake up all
        applications to redraw their exposed areas under the window
        you're dragging than it is for compiz to just recomposite that
        out of textures already in video memory.
        
5) If you don't know what you're talking about, will being excessively
dismissive and assertive make you right?

        No.
        
Kristian



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