gdk:screen-rgba-visual (screen)

screen -- a gdk:screen object

The gdk:visual object to use for windows with an alpha channel or nil if the capability is not available.

Gets a visual to use for creating windows with an alpha channel. The windowing system on which GTK is running may not support this capability, in which case nil will be returned. Even if a non-nil value is returned, it is possible that the window's alpha channel will not be honored when displaying the window on the screen: in particular, for X11 an appropriate windowing manager and compositing manager must be running to provide appropriate display.

This functionality is not implemented in the Windows backend.

For setting an overall opacity for a toplevel window, see the gdk:window-set-opacity function.