GeoExt: Excluding some of the layers from the legend

Question

Openlayers and GeoExt for producing a web map. The map has a legend panel generated by GeoExt. By default, GeoExt grabs the details of every layers from the map and create a legend for all the layers. However, I would like to exclude some of the layers to be displayed from the legend, what should I do to achieve this?

    legendPanel = new GeoExt.LegendPanel({
    map: map,
    title: 'Legend Panel',
    renderTo:'description',
    border: false,
    autoScroll: true,
    defaults: {
        style: 'padding:5px',           
        baseParams: {
            FORMAT: 'image/png',
            LEGEND_OPTIONS: 'forceLabels:on;fontName=Verdana;fontSize:11'
            }
        }
    });

Thanks!

Answer 1

There is actually quite detailed documentation about the issue here. Here's some quotes from the site relating to your issue.

The LegendPanel will include legends for all the layers in the layerStore it is configured with, unless the layer is configured with displayInLayerSwitcher: false, or a layer record has a hideInLegend field with a value of true. Additional filtering can be done by configuring a filter on the LegendPanel.

Here is my guessing code that applies the filter function:

    legendPanel = new GeoExt.LegendPanel({
    map: map,
    title: 'Legend Panel',
    renderTo:'description',
    border: false,
    autoScroll: true,
    filter: function(record){
        //Your filter function goes here, note that the function is processed on each layer.
        // Return false for those layers you want to exclude.
    },
    defaults: {
        style: 'padding:5px',           
        baseParams: {
            FORMAT: 'image/png',
            LEGEND_OPTIONS: 'forceLabels:on;fontName=Verdana;fontSize:11'
            }
        }
    });