Tooltips not supported on textbox and combobox?

<zk>
        <textbox tooltip="msg"/>
        <button tooltip="msg" label="test"/>
        <label tooltip="msg">some label</label>
        <combobox  tooltip="msg">
              <comboitem label="Simple and Rich" />
              <comboitem label="Cool!" />
              <comboitem label="Thumbs Up!" />
        </combobox>

	<popup id="msg" width="300px">
		Here is the tooltips !
	</popup>
</zk>