1. glcontextid function is replaced by gstreamer gst_gl_context_new_wrapped .
2. call gst_init before gst_gl_display_new , seems gst_gl_display_new depends
on gst_allocator_register , which only worked after gst_init called
3. flush gstreamer OpenGL context before using shared texture, fix
flicker problem.
https://bugzilla.gnome.org/show_bug.cgi?id=735566
Before:
GST_GL_PLATFORM=cocoa GST_GL_WINDOW=cocoa
gst-launch-1.0 videotestsrc ! glimagesink
After:
GST_GL_PLATFORM=cgl GST_GL_WINDOW=cocoa
gst-launch-1.0 videotestsrc ! glimagesink
but still pass --enable-cocoa to configure script
because currently it can only be used with cocoa API.
We could later have cgl/gstglcontext_cgl.h that manages
a CGLContextObj directly and cocoa/gstglcontext_cocoa.h
would just wrap it.
So that it could be used with other Apple's window APIs.
https://bugzilla.gnome.org/show_bug.cgi?id=729245
