public bool is_composited ()
Warning: is_composited is deprecated since "3.22".
Whether this can rely on having its alpha channel drawn correctly.
Use is_composited instead.
On X11 this function returns whether a compositing manager is running for this’s screen.
Please note that the semantics of this call will change in the future if used on a widget that has a composited window in its hierarchy (as set by set_composited).
true if the widget can rely on its alpha channel being drawn correctly.