gdk:window-clip-region (window)

window -- a gdk:window object

A cairo:region-t instance. This must be freed with the cairo:region-destroy function when you are done.

Computes the region of a window that potentially can be written to by drawing primitives. This region may not take into account other factors such as if the window is obscured by other windows, but no area outside of this region will be affected by drawing primitives.