gdk-window-at-pointer ()

window -- window under the mouse pointer
win-x -- a :int with the origin of the window under the pointer
win-y -- a :int with the origin of the window under the pointer

Obtains the window underneath the mouse pointer, returning the location of that window in win-x, win-y. Returns nil if the window under the mouse pointer is not known to GDK. The function gdk-window-at-pointer has been deprecated since version 3.0 and should not be used in newly written code. Use the function gdk-device-window-at-position instead.