Description
GtkPixmapMenuItem works like a normal GTK menu item, but you can insert a
arbitrary widget (most often a pixmap widget), which is displayed 
at the left side. The advantage is that indentation is handled the 
same way as GTK does (i.e if you create a menu with a gtk_check_menu_item, 
all normal menu items are automatically indented by GTK - so if you 
use a normal menu item to display pixmaps at the left side, the pixmaps 
will be indented, which is not what you want. This widget solves 
the problem).