The following classes have been checked:
<gtk-action-group>
<gtk-box>
<gtk-button>
<gtk-button-box> 
<gtk-cell-renderer-toggle>
<gtk-cell-renderer-text>
<gtk-check-button>
<gtk-combo-box>
<gtk-container>
<gtk-dialog>
<gtk-entry>
<gtk-frame>
<gtk-hbox>
<gtk-hbutton-box>
<gtk-hpaned>
<gtk-image>
<gtk-label>
<gtk-list-store>
<gtk-menubar>
<gtk-message-dialog>
<gtk-paned>
<gtk-scrolled-window>
<gtk-size-group>
<gtk-statusbar>
<gtk-table>
<gtk-text-buffer>
<gtk-text-iter>
<gtk-text-view>
<gtk-toolbar>
<gtk-tree-selection>
<gtk-tree-view>
<gtk-tree-view-column>
<gtk-ui-manager>
<gtk-vbox>
<gtk-vbutton-box>
<gtk-vpaned>
<gtk-widget>
<gtk-window>
