[pygtk] Setting a custom pitmap on a stock icon

[Jeffrey Barish]

I created a stock icon.  It works fine using the default bitmap.  Now I
would like to set the bitmap for the stock item when it is rendered at a
specific size.  Here is the code that I am using:

pb = gtk.gdk.pixbuf_new_from_file(icon_file)
iconset = gtk.IconSet(pb)

pb2 = gtk.gdk.pixbuf_new_from_file(icon_file_2)
iconsource = gtk.IconSource()
iconsource.set_pixbuf(pb2)
iconsource.set_size(gtk.ICON_SIZE_DND)
iconset.add_source(iconsource)
iconfactory.add(icon_name, iconset)

With this code, I get the image from icon_file_2 at all sizes.  I expect to
see that image only during a drag (because of the set_size call).  Any idea
what I am doing wrong?
-- 
Jeffrey Barish