kwin/COMPOSITE_TODO

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* = not done
/ = work in progress
? = should it be done?
See the HACKING file for KWin details. The composite-related sources are mostly
composite.cpp and scene_opengl.cpp (TODO: add comments and general overview).
Sources:
- glcompmgr : http://lists.freedesktop.org/archives/xorg/2006-July/017006.html ,
http://www.mail-archive.com/compiz%40lists.freedesktop.org/msg00023.html
- simple and easy to understand
- works even without texture_from_pixmap extension
- claims to support several different gfx cards
- compiz : git clone git://anongit.freedesktop.org/git/xorg/app/compiz
- the ultimate <whatever>
- glxcompmgr : git clone git://anongit.freedesktop.org/git/xorg/app/glxcompgr
- a rather old version of compiz, but also simpler and as such simpler
to understand
- libcm (metacity) : cvs -d :pserver:anonymous@anoncvs.gnome.org:/cvs/gnome co libcm
- no idea about it
TODO:
* Check/make it work with other gfx cards
- I've tested only with nvidia with the 9625 beta drivers so far
* latest stable nvidia drivers don't quite work, the COPY_BUFFERS
or REFRESH_DRAWABLES workaround from glcompmgr should take care of that
- the COPY_BUFFERS hack, if I'm getting it right, just creates a copy
of the X Pixmap first, so just always using ALPHA_CLEAR_COPY hack
in KWin should do the same
- I have absolutely no idea about other gfx cards, needs to be tested
* ati
* intel
* who knows what else
? Xgl support
- Compiz itself doesn't work when compiled with the libGL from nvidia,
it ships its own and links against it
? might be worth trying to use that libGL as well
- it may be just because of the special libGL, but when testing with Xgl
it even seemed non-conformant - none of the provided configs had
GLX_RENDER_TYPE with GLX_RGBA_BIT even though required by GLX
and other funny things. Indeed, it may be just me being still pretty
clueless about these things.
* is there a good reason to support Xgl? With the 9625 nvidia drivers
it seems to work fine without them
? AIGLX support
- no idea about this at all
* find out if it works
* XComposite overlay window
- X.Org 7.1 and newer have XComposite extension version 0.3, which allows
creating an overlay window to paint to instead of painting to the root window
- I still run older X.Org here
- the code in glcompmgr for this is in HAVE_OVERLAYS, stealing primarily from
here should be better since it's simpler and the code so far has been
modelled more after glcompmgr
- the code in compiz for this is in USE_COW
* use double-buffering with the overlay window - kwin already has code
for double-buffered destination drawable, but I haven't been able to test it
* when relying on extensions, detect that they are available
- some of the glcompmgr code probably depends on OpenGL/GLX extensions that may
not be always available, probably the same with compiz
* find out which code relies on extensions and add checks
? alpha clear hack
* find out if it affects performance
* if yes, try to find a better way of solving the problem
- since kompmgr has an option to make only the decoration transparent,
it should be possible to do the same here - if the window has alpha and a decoration
or if there should be only the decoration transparent, paint first the contents
and then the decoration - this should make it possible to paint the decoration
without the random alpha that is right now handled by the alpha hack
/ design framework for graphical effects
- modelling it after compiz seems to make a lot of sense
* update only those parts of the screen that have been changed
- for paintSimpleScreen() - it currently sets region to the whole screen
* instead of using glXSwapBuffers() there should be glCopyPixels() used
- compiz has such code in evenLoop() in the if() block for COMP_SCREEN_DAMAGE_REGION_MASK
* perhaps syncing to vblank will be needed to avoid flicker
* XCopyArea() should not update the whole screen but only the affected areas