Alexandros Frantzis authored Oct 19, 2018 and Pekka Paalanen committed Feb 06, 2019

Implement the set_acquire_fence request of the
zwp_surface_synchronization_v1 interface.

The implementation uses the acquire fence in two ways:

1. If the associated buffer is used as GL render source, an
   EGLSyncKHR is created from the fence and used to synchronize
   access.
2. If the associated buffer is used as a plane framebuffer,
   the acquire fence is treated as an in-fence for the atomic
   commit operation. If in-fences are not supported and the buffer
   has an acquire fence, we don't consider it for plane placement.

If the used compositor/renderer doesn't support explicit
synchronization, we don't advertise the protocol at all. Currently only
the DRM and X11 backends when using the GL renderer advertise the
protocol for production use.

Issues for discussion
---------------------

a. Currently, a server-side wait of EGLSyncKHR is performed before
   using the EGLImage/texture during rendering. Unfortunately, it's not clear...