Gtk+ Drop down menu from Toolbar item

[chen donghai zte com cn]

Hi everyone:
    i need to drop down menu
from toolbar item by gtk2.x, but don't know how to do it?
if use gtk_menu_tool_button_new, there
is down arrow icon to show menu on the right of toolbutton,
but want to show menu by toolbutton
not the down arrow icon.

please  refer fo http://stackoverflow.com/questions/9132440/gtk-drop-down-menu-to-toolbar-item



Thank you very much