This helper shall be used by classes implementing the #GstVideoOverlay
interface that want the render rectangle to be controllable using
properties. This helper will parse and set the render rectangle calling
gst_video_overlay_set_render_rectangle().
This helper shall be used by classes implementing the #GstVideoOverlay interface that want the render rectangle to be controllable using properties. This helper will parse and set the render rectangle calling gst_video_overlay_set_render_rectangle().