1) We know that gst_wayland_sink_render() will commit the surface
in the same thread a little later, as gst_wl_window_set_video_info()
is always called from there, so we can save the compositor from
some extra calculations.
2) We should not commit a resize with the new video info while we are still
showing the buffer of the previous video, with the old caps, as that
would probably be a visible resize glitch.
* own_surface is not needed anymore
* gst_wl_window_from_surface is not used externally anymore
* many initializations to 0 are not needed (GObject does them)
This means that the given surface in set_window_handle can now be
the window's top-level surface on top of which waylandsink creates
its own subsurface for rendering the video.
This has many advantages:
* We can maintain aspect ratio by overlaying the subsurface in
the center of the given area and fill the parent surface's area
black in case we need to draw borders (instead of adding another
subsurface inside the subsurface given from the application,
so, less subsurfaces)
* We can more easily support toolkits without subsurfaces (see gtk)
* We can get properly use gst_video_overlay_set_render_rectangle
as our api to set the video area size from the application and
therefore remove gst_wayland_video_set_surface_size.
This drops the ugly GstWaylandWindowHandle structure and is much
more elegant because we can now request the display separately
from the window handle. Therefore the window handle can be requested
in render(), i.e. when it is really needed and we can still open
the correct display for getting caps and creating the pool earlier.
This change also separates setting the wl_surface from setting its size.
Applications should do that by calling two functions in sequence:
gst_video_overlay_set_window_handle (overlay, surface);
gst_wayland_video_set_surface_size (overlay, w, h);
This is the initial implementation, without the GstVideoOverlay.expose()
method. It only implements using an external (sub)surface and resizing
it with GstWaylandVideo.
