Rewrote SurfaceFlinger's buffer management from the ground-up.
The design now support an arbitrary number of buffers per surface, however the current implementation is limited to four. Currently only 2 buffers are used in practice.
The main new feature is to be able to dequeue all buffers at once (very important when there are only two).
A client can dequeue all buffers until there are none available, it can lock all buffers except the last one that is used for composition. The client will block then, until a new buffer is enqueued.
The current implementation requires that buffers are locked in the same order they are dequeued and enqueued in the same order they are locked. Only one buffer can be locked at a time.
eg. Allowed sequence: DQ, DQ, LOCK, Q, LOCK, Q
eg. Forbidden sequence: DQ, DQ, LOCK, LOCK, Q, Q
This change makes SurfaceHolder.setType(GPU) obsolete (it's now ignored).
Added an API to android_native_window_t to allow extending the functionality without ever breaking binary compatibility. This is used to implement the new set_usage() API. This API needs to be called by software renderers because the default is to use usage flags suitable for h/w.
we can't use a texture of 1/4th of the screen for the dim layer, because the mdp internal input resultion is alwyas integers and for very small blits of a couple pixels the scale factor can get way out of range, for instance for a 7 pixels source, the scale factor would be either 7 (7/1) or 3.5 (7/2) instead of 4 (7/1.75). This caused the mdp to fail in some cases and revert to software. we now always use a texture of the actual screen size, so the problem will never happen. This burns 300KB of pmem instead of 21KB. On devices with a larger screen we might want to use a smaller texture and tile it by hand.
Mathias Agopian