gdk:display-rgba (object)

object -- a gdk:display object
setting -- true if the display supports an alpha channel

The accessor for the rgba slot of the gdk:display class returns whether surfaces on the display are created with an alpha channel.

Even if a true is returned, it is possible that the alpha channel of the surface will not be honored when displaying the surface on the screen. In particular, for X an appropriate windowing manager and compositing manager must be running to provide appropriate display. Use the gdk:display-is-composited function to check if that is the case.

On modern displays, this value is always true.