Dialog windows should be set transient for the main application window they were spawned from. This allows <link linkend="gtk-X11-arch">window managers</link> to e.g. keep the dialog on top of the main window, or center the dialog over the main window. gtk_dialog_new_with_buttons() and other convenience functions in GTK+ will sometimes call gtk_window_set_transient_for() on your behalf. Passing %NULL for @parent unsets the current transient window. On Windows, this function puts the child window on top of the parent, much as the window manager would have done on X.