When we are painting a stack of 5-10 maximized windows, the
standard bottom-to-top method of drawing every actor results
in a tremendous amount of overdraw and can easily max out
the available memory bandwidth on a low-end* graphics chipset.
It's even worse if window textures are being accessed over
the AGP bus.
When we have opaque windows, we can go ahead and compute visibility
ourselves (in classic X-server fashion) and use that information to
restrict drawing obscured actors.
* Add MutterWindowGroup - a ClutterGroup subclass with logic
for figuring out obscured regions.
* Add mutter_window_get_obscured_region() to get the region
obscured by that window.
* Add mutter_shaped_texture_set_clip_region() to hint
a clip region to the painting code; this is set based on
the computed visible region of MutterWindowGroup.
* Add tidy_texture_frame_set_needs_paint() to hint that the
paint can be skipped entirely; this is used when we detect
that the window shadow is entirely obscured.
http://bugzilla.gnome.org/show_bug.cgi?id=587344
Mutter is a Clutter-based compositing manager. So, remove the code for
the XRender-based compositor, and make it mandatory to have XComposite,
XRender and Clutter.
Run-time support for non-composited operation is left for now.
* src/compositor/mutter/: Move files from this subdirectory into
the main compositor/ directory.
* compositor/compositor-xrender.ccompositor/compositor-xrender.h:
Remove
* include/compositor-clutter.h: Remove this stray file, it had been
replaced with compositor-mutter.h some time back.
http://bugzilla.gnome.org/show_bug.cgi?id=581813
