gdk-offscreen-window-embedder (window)

window -- a gdk-window object
embedder -- the gdk-window that window gets embedded in

The embedding gdk-window object, or nil if window is not an embedded offscreen window.

The function gdk-offscreen-window-embedder gets the window that window is embedded in. The function (setf gdk-offscreen-window-embedder) sets window to be embedded in embedder.

To fully embed an offscreen window, in addition to calling this function, it is also necessary to handle the "pick-embedded-child" signal on embedder and the "to-embedder" and "from-embedder" signals on window.