How to add a layer to SelectFeature without losing existing selections?

Question

I'm using an OpenLayers.Control.SelectFeature for selections on multiple layers. However, when I add a layer using setLayer(), my selections on the other layers are lost.

Anyone know how to work around this? I would like to keep my existing selections on other layers when I add a layer to the SelectFeature control.

Here is an example: MY EXAMPLE

Update:

I'm aware that this is part of the API. But i'm looking for a work around.

/**
 * APIMethod: setLayer
 * Attach a new layer to the control, overriding any existing layers.
 *
 * Parameters:
 * layers - Array of {<OpenLayers.Layer.Vector>} or a single
 *     {<OpenLayers.Layer.Vector>}
 */
setLayer: function(layers) {
    var isActive = this.active;
    this.unselectAll();
    this.deactivate();
    if(this.layers) {
        this.layer.destroy();
        this.layers = null;
    }
    this.initLayer(layers);
    this.handlers.feature.layer = this.layer;
    if (isActive) {
        this.activate();
    }
},

Answer 1

You could modify setLayer method of SelectFeature control:

OpenLayers.Control.SelectFeature.prototype.setLayer = function(layers) {
    var isActive = this.active;
    //this.unselectAll(); <- what you need
    this.deactivate();
    if(this.layers) {
        this.layer.destroy();
        this.layers = null;
    }
    this.initLayer(layers);
    this.handlers.feature.layer = this.layer;
    if (isActive) {
        this.activate();
    }
}