gdk-window-modal-hint (window)

window -- a toplevel gdk-window object
modal -- true if the window is modal, false otherwise

Whether or not the window has the modal hint set.

The function gdk-window-modal-hint determines whether or not the window manager is hinted that window has modal behaviour.

The application can use this hint to tell the window manager that a certain window has modal behaviour. The window manager can use this information to handle modal windows in a special way.

You should only use this on windows for which you have previously called the function gdk-window-set-transient-for.