Button with menu

[Tobias Weber <towb celvina de>]

Hi,
having three kinds of items that can be added to a list, I want to  
have the plus button pop up a menu similar to this:

http://img.skitch.com/20090711-pfg7pfreqrdq1rhhjun7hixne2.png

I tried using Gtk(Toggle)Button with GtkMenu, but don't see a way to  
position the menu attached to the button instead of below the cursor,  
nor to show the button depressed while the menu is open.

It's easier with a ComboBox, unless I want an image like the stock add  
button. Also the 'button label' would be part of the menu.

Any other options?