This means we cannot access [view layer] or view.bounds from the OpenGL
thread. This also means that we need to call the main thread when
setting the window handle. However, we cannot perform that
synchronously as that may deadlock with the application performing the
set_window_handle() call.
We need to defer the actual update and run it asynchronously and wait
for the window handle update internally at each point it is needed.
Fixes: https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/372
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/681>
All code interacting with Objective-C objects should now use Automated
Reference Counting rather than manual memory management or Garbage
Collection. Because ARC prohibits C-structs from containing
references to Objective-C objects, all such fields are now typed
'gpointer'. Setting and gettings Objective-C fields on such a
struct now uses explicit __bridge_* calls to tell ARC about
object lifetimes.
https://bugzilla.gnome.org/show_bug.cgi?id=777847
Execute GL calls without marshalling them to the context thread. In the cocoa
and eagl backends calling gst_gl_context_activate is cheap and therefore calling
it on the current thread and serializing GL calls with a per-context lock is
more efficient (faster and has less overhead) than marshalling everything to the
context thread.
This optimization cuts a large overhead in g_poll (continuously waking up the
context thread) and in g_mutex_*/g_cond_* (waiting for results from the context
thread).
