gdk-window-unmaximize (window)

window -- a toplevel gdk-window object

Unmaximizes the window. If the window was not maximized, then this function does nothing.

On X11, asks the window manager to unmaximize window, if the window manager supports this operation. Not all window managers support this, and some deliberately ignore it or do not have a concept of "maximized"; so you cannot rely on the unmaximization actually happening. But it will happen with most standard window managers, and GDK makes a best effort to get it to happen.

On Windows, reliably unmaximizes the window.