gdk:window-toplevel (window)

window -- a gdk:window object

The toplevel gdk:window window containing window.

Gets the toplevel window that is an ancestor of the window. Any window type but :child is considered a toplevel window, as is a :child window that has a root window as parent.

Note that you should use the gdk:window-effective-toplevel function when you want to get to a window's toplevel as seen on screen, because the gdk:window-toplevel function will most likely not do what you expect if there are offscreen windows in the hierarchy.