Re-did the painting logic, and document it.
It is unclear to me what is the previous painting logic. But the current
one is basically this:
1. Go through all windows top to bottom, and put visible windows (not
unmapped, opacity > 0, etc) into a linked list, from bottom to top
2. Accumulate a region of ignore on each window, which is basically the
region of screen that is obscured by all the windows above current
one.
3. Paint all the visible windows from bottom to top. Subtract the region
of ignore from the painting region. If we need to paint shadow, we
subtract the body of the window from the shadow painting region too,
because we don't want shadow behind the window.
4. region of ignore is invalidated when window stack change, an
window on top moved or changed shape, when window changed between
opaque and transparent, etc.
Notes:
It is unclear whether all the different shapes of a window (extents,
noframe, border, bounding shape, etc) are calculated correctly or not.
It is unclear if window shape related events are handled correctly or
not. Need more testing.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Change `win *` to `win **`, because a window could be freed by the
callback, so we can set `*w` to NULL to communicate that.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Also remove some debug function calls (there are better tools for opengl
debugging now). Also remove copysubbuffermesa
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Instead use win_has_alpha to check for alpha channel, window mode is
reserved for determine if the window is possibly transparent.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
If an X event is received at a very specific point in time, it can trigger
a race condition in Xlib. Said event will be read, but Xlib will
nonetheless be completely unaware of the event.
This cause compton to sometimes block on select() while there are events
ready to be processed. If the event is a damage report, screen freeze
will happen until some other event is received.
The proper fix is to switch to xcb for event handling, thus avoid this
problem entirely.
There seems to be a race between DamageAdd (what the client uses
to report damage to Xserver) and DamageSubtract (what compton uses
to clear the reported damage, so it can receive new ones). I am not
sure how to confirm this. But this (terrible) workaround seems to
solve this problem.
* Move code around
* Remove unneeded forward declaration
* Rename win->damaged to win->ever_damaged, to be less confusing
* Expose debug functions even when DEBUG is not enabled. Compiler
would remove the dead code for us anyway.
* Some code cleanup
Also move static function prototypes out of compton.h. Seems like the
previous developers didn't know what header files are for.
Seems to have bugs after the split.
Under extreme race conditions (window A close at the same time as window
B create), there can be multiple windows with same id in compton's window
list. If at this point window B closes itself as well, finish_destroy_win
might destroy a different window as what's passed to destroy_callback.
This can be a problem because someone can still hold a reference to that
window (e.g. 't' in paint_preprocess), and there's no way to clear that
reference. If finish_destroy_win always destroy the same window passed
to destroy_callback, this will not be a problem.
Yuxuan Shui