set_transient_for() is used to set a dialog or popup window as a temporary child of the toplevel window it is associated with. This prevents there being an additional icon for the transient message in the taskbar, and also allows the transient window to take on the behaviour of the parent window, e.g. if the parent is minimized the child will minimize along with it.

This method does not work in the win32 version of GTK+ currently used by PHP-GTK, but as the bug causing the problem has now been fixed in Gnome CVS it would be sensible to use it.

Attempting to delete the parent window before destroying the transient window produces a gdk warning on win32. To avoid this, always use set_modal() where you have used set_transient_for() .