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.
First, the window manager tells us when a surface is no longer needed. At this point, several things happen:
- the surface is removed from the active/visible list
- it is added to a purgatory list, where it waits for all clients to release their reference
- it destroys all data/state that can be spared
Later, when all clients are done, the remains of the Surface are disposed off: it is removed from the purgatory and destroyed.
In particular its gralloc buffers are destroyed at that point (when we're sure nobody is using them anymore).
Surfaces are now destroyed once all references from the clients are gone, but they go through a partial destruction as soon as the window manager requests it.
This last part is still buggy. see comments in SurfaceFlinger::destroySurface()
