A context menu item to popup opacity slider to change opacity of Layer.
Sample code showing how to include LayerNodeMenuItems. Optionally pass your own menu items.
      .
      .
      {
       xtype: 'hr_layertreepanel',
   FOR NOW: TODO: something smart with ExtJS plugins..
       contextMenu: [{xtype: 'hr_layernodemenuzoomextent'}, {xtype: 'hr_layernodemenustyle'}]);
},
      {
        // The MapPanel
        xtype: 'hr_mappanel',
        id: 'hr-map',
        region: 'center',
        .
        .