Check if the window and all ancestors of the window are mapped. (This is not necessarily "viewable" in the X sense, since we only check as far as we have GDK window parents, not to the root window.)
%TRUE if the window is viewable
See Implementation
Check if the window and all ancestors of the window are mapped. (This is not necessarily "viewable" in the X sense, since we only check as far as we have GDK window parents, not to the root window.)