One of the current limitations of EGLStreams is that there's no way to
resize a surface consumer without re-creating the entire stream.
Therefore, while resizing, clients will send wl_surface::attach requests
so the compositor can re-create its endpoint of the stream, but no
buffer will be available actually. If we proceed with the rest of the
attach operation we'll be presenting an empty buffer.
In order to fix this, a separate wl_eglstream_controller protocol has
been introduced that clients can use to request a stream re-creation
without overloading wl_surface::attach for that purpose.
This change adds the required logic to create the corresponding
wl_eglstream_controller global interface that clients can bind to.
Whenever a client requests a stream to be created, we just need to
create and realize the new EGLStream buffer. The same buffer resource
will be given at a later time to wl_surface::attach, whenever new
content is made available by the application, so we can proceed to
acquire the stream buffer and update the surface state.
https://bugzilla.gnome.org/show_bug.cgi?id=782575
This commit adds for a new type of buffer being attached to a Wayland
surface: buffers from an EGLStream. These buffers behave very
differently from regular Wayland buffers; instead of each buffer
reperesenting an actual frame, the same buffer is attached over and
over again, and EGL API is used to switch the content of the OpenGL
texture associated with the buffer attached. It more or less
side-tracks the Wayland buffer handling.
It is implemented by creating a MetaWaylandEglStream object, dealing
with the EGLStream state. The lifetime of the MetaWaylandEglStream is
tied to the texture object (CoglTexture), which is referenced-counted
and owned by both the actors and the MetaWaylandBuffer.
When the buffer is reattached and committed, the EGLStream is triggered
to switch the content of the associated texture to the new content.
This means that one cannot keep old texture content around without
copying, so any feature relying on that will effectively be broken.
https://bugzilla.gnome.org/show_bug.cgi?id=773629
