window partially transparent,
with opacity 0 being fully transparent and 1 fully opaque. (Values
of the opacity parameter are clamped to the [0,1] range.) gdkWindowSetOpacity(object, opacity)objectGdkWindowopacitygdkScreenGetRgbaColormap.
For making non-toplevel windows translucent, see
gdkWindowSetComposited.
Since 2.12