kwin/COMPOSITE_TODO

This file lists TODO items for the compositing code.

See file COMPOSITE_HOWTO for setting up kwin_composite.
See file HACKING for details on developing KWin, including building
    the kwin_composite branch.
See effects/howto.* for a HOWTO on writting effects.
See documentation in source (mainly in scene.cpp) for description
    of the design of the compositing framework.

TODO
=================================

* = not done, will be either done by me, or should be at least discussed first with me
+ = not done, I don't plan on doing it that soon
    - in other words, these should be the best ones for you if you want to help
! = like +, but they should be relatively simple
    - in other words, these should be the best if you want to get started with the code
/ = work in progress
? = should it be done?
% = should be probably done later, during cleanups and preparations for being stable


General TODO
=================================

? 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

? wait for decoration repaints
    - it is sometimes visible that the window contents are painted first and the decoration
        only afterwards with a small delay
?       - this has been already greatly improved by r632378, so it's maybe not worth it anymore
    - maybe posted paint events need to be processed immediatelly, or maybe the compositing
        code should not update the window until the decoration is finished painting

! compile even without OpenGL or XRender
    - kwin_composite currently requires both OpenGL and XRender to build
    - compiling without either results in compile errors, needs to be fixed
!   - scene_xrender.cpp also requires XFixes
!   - check whether it compiles fine without XComposite/XDamage

? Expose events for overlay window - is it necessary to track it, like with root window?

% paint throttling
    - there's 5ms grace period per repaint to avoid overloading the system with just compositing
        and not letting the system do anything else - check and evaluate 

+ support for new window types from the wm spec for compositing
    - this will have to be done in Qt, kdecore and kwin

* handle properly stacking order of deleted windows for showing in effects

* handle properly deleted windows that reappear (windowReadded() function?)

/ consider using an extra class for representing deleted windows
    - cleaning up Client/Unmanaged instances may still leave e.g. timers around if they're overlooked
    - an extra class could copy some interesting data and "replace" the old instance

% during screensaving, do no let non-screensaver windows show above screensaver
    - kdesktop_lock watches for such things and raises again, but there's a small gap

% nvidia drivers by default use fake refresh rates as a workaround for some X limitations
    - see the DynamicTwinView section in nvidia README
    - this makes KWin repaint at a different rate than it should


OpenGL TODO
=================================

/ Check/make it work with other gfx cards

? 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 and there's AIGLX
    
+ AIGLX support
    - kind of works, needs more work
+   - it needs indirect rendering, should be autodetected and disabled somehow
%   - may require LIBGL_ALWAYS_INDIRECT set with older X.org
        (http://lists.kde.org/?l=kwin&m=116439615124838&w=2)
        (http://lists.freedesktop.org/archives/xorg/2006-December/020323.html)

/ GL_ARB_texture_rectangle vs GL_ARB_texture_non_power_of_two
%   - works; bugs in tfp_mode with power_of_two textures
        - ati (others?): power_of_two windows are drawn white unless non-tfp_mode
            is forced in findTextureTarget()

? in SceneOpenGL::bindTexture() with tfp_mode, with some gfx cards it seems
    to be faster to not short-circuit the texture binding when there's been
    no damage

+ strict binding
    - there is code to support strict binding as required by AIGLX, but it's disabled, because
        copy_buffer in bindTexture() ensures strict binding as a side-effect
    - since copy_buffer hack should be removed in the future, strict binding will need to be enabled then
    - http://lists.kde.org/?l=kwin&m=116363084129170&w=2

% bindTexture() optimize copied areas
    - right now bindTexture() updates every damaged area and resets the window damage
    - it might make things faster to update only areas that need to be repainted
        and keep the rest damaged until needed

% clipping optimization
    - like XRender code has paintTransformedScreen(), avoid painting parts that are
        obscured (makes a difference with many windows open)
    - http://lists.kde.org/?l=kwin&m=116585618111882&w=2

+ shm mode needs support for more data formats than GL_BGRA in order to support e.g. 16bpp mode
    - http://www.xfree86.org/current/glTexImage2D.3.html

% with current nvidia glXCreatePixmap in tfp mode fails with pixmaps 32x32 and smaller


XRender TODO
==============================

+ SceneXrender::Window::performPaint() doesn't use saturation
+ SceneXrender::Window::performPaint() doesn't use brightness


Effects framework TODO
==============================

* more notification functions for effects are needed
    - currently there are only very few notification functions (windowAdded, windowActivated,...)
!   - window state changes
    ? more

* shadows

/ support for grabbing input
    - during some more complicated effects, input (at least mouse) should be disabled,
        because currently there is no way to do input redirection

? pre-paint pass should be done completely before the paint pass
    - currently prePaintWindow() is done only after paintScreen() has already started,
        which means that if an effect sets PAINT_WINDOW_TRANSFORMED it needs to set it
        also in prePaintScreen()

* PAINT_DISABLED turning off from effects needs some improvement
    - a window may have painting disabled for various reasons and their numbers may increase
        over time
        - so e.g. an effect showing minimized windows cannot simply turn off DISABLED
            for minimized windows, because it may be disabled also for other reasons
        - there should be some utility function that will be called by the effect
            with arguments saying which disabled windows it wants enabled

+ EffectWindow should be completely opaque when kept as the only API for effects
    - no inlines, etc.


Effects TODO
===============================

+ adapt the kcontrol module used by Kompmgr
    - in kcmkwin/kwinoptions
!   - uses ~/.xcompmgr, convert to use normal KConfig
?   - I don't think these effects should be plugins or anything like that,
        probably simply write to kwinrc and use the Option class in KWin

+ implements all effects Kompmgr could do
+   - all effects from the Opacity tab should be already doable
!       - applying translucency only to the decoration
            - use clientSize() and clientPos() from Client
            - see also the alpha clear hack todo entry
!       - not usign ARGB visuals
            - just clear the alpha channel in the alpha clear hack
            - or do it while painting (see also the alpha clear hack todo entry)
!       - the rest - should be simple
*   - shadows
        - framework is not ready for them yet (see the todo entry)
+   - tab Effects
!       - fade-in should be simple
+       - fade between changes
            - will need notification about opacity changes
            - not sure if this is doable for other opacity changes then the ones
                initiated by the user or by the application
*       - fade-out needs framework for disappearing windows (see the todo entry)

+ minimize/shade effects
    - to replace the ones from KWin core
/       - minimizing
            - check support for it and the avoid_animation flag
+       - shading
            - shading will probably need special support

/ zoom effect
    - enlarge a portion of the screen

+ logout effect
*   - should be triggered by ksmserver somehow

+ effects to replace widget effects (the ones in the Effects tab in "kcmshell style")
+   - needs support for new window types from the current draft of the EWMH WM spec
+       - needs patching Qt, netwm* classes in kdecore

/ showfps effect
    - for debugging, just shows transparent fps in some corner
    - just painting the number in paintScreen() should do, with glPushMatrix() and glLoadIdentity()
        to avoid all transformations
+   - needs bindPixmapToTexture() or something like that, for displaying the text
    - should also detect kwin being idle - it probably should detect in pre-paint that the only
        damage is its own area and avoid damaging for the next round in post-paint

+ debugpaint effect
    - should show what is damaged during each repaint step
    - probably just e.g. paint a red almost transparent area over damaged areas
    - needs special care to avoid causing infinite loops by its own damage (i.e. it damages
        part of screen to clear its own painting, that triggers itself again next repaint)

? other effects

+ merge fadein and fadeout effects
    - so that they don't conflict and share the progress

+ virtual desktop change effects
+   - ... yes, you guessed it, the cube
+   - something that presents all virtual desktops as being in grid (as in pager)
        and zooms out of the old one and into the new one
    - or whatever