Detecting click on map outside features in OpenLayers 2?

Question

How to detect click on map outside features from two vector layers in OpenLayers 2? Here is a code that alerts on selecting feature:

var layer1 = new OpenLayers.Layer.Vector("Vector Layer 1");
var layer2 = new OpenLayers.Layer.Vector("Vector Layer 2", {
    styleMap: new OpenLayers.StyleMap({ "default": {
    'fillColor': '#669933',
    'pointRadius': 6
  }})
});
for (var i=0; i<10; i++) {
    layer1.addFeatures([new OpenLayers.Feature.Vector(
    new OpenLayers.Geometry.Point((360 * Math.random()) - 180, (180 * Math.random()) - 90)
  )]);
    layer2.addFeatures([new OpenLayers.Feature.Vector(
    new OpenLayers.Geometry.Point((360 * Math.random()) - 180, (180 * Math.random()) - 90)
  )]);
}
map.addLayers([layer1, layer2]);

var select = new OpenLayers.Control.SelectFeature([layer1, layer2], {
    onSelect: function (feature) {
    alert("selected");
  }
});
map.addControl(select);
select.activate();

Now I want to alert "all deselected" when user resets the selection.

Example: http://jsfiddle.net/f6rvj7q9/

Answer 1

You will need to listen for the Unselect event, then use a short timeout to ensure another feature hasn't been selected

var selected = false;
var select = new OpenLayers.Control.SelectFeature([layer1, layer2], {
    onSelect: function (feature) {
    selected = true;
    alert("selected");
  },
    onUnselect: function (feature) {
    selected = false;
    setTimeout(function(){ if (!selected) alert("not selected"); }, 1);
  }
});

It is also possible to listen for clicks anywhere on a map (for example if you need to make WMS GetFeatureInfo requests). See the source of this example http://dev.openlayers.org/examples/click.html