The menu example in the examples/menu directory of the GTK+ distribution implements a popup menu with this technique:
static gint button_press (GtkWidget *widget, GdkEvent *event)
{
if (event->type == GDK_BUTTON_PRESS) {
GdkEventButton *bevent = (GdkEventButton *) event;
gtk_menu_popup (GTK_MENU(widget), NULL, NULL, NULL, NULL,
bevent->button, bevent->time);
/* Tell calling code that we have handled this event; the buck
* stops here. */
return TRUE;
}
/* Tell calling code that we have not handled this event; pass it on. */
return FALSE;
}