openlayers 3 - Click on polygon boundaries

Question

On a map, I have drew a polygon and I want to popup some information when I click on ONLY boundaries of the polygon. Do you have any solutions to force the selection on boundaries?

            var featureContext = new ol.Feature({
                geometry: new ol.geom.Polygon([polyCoords])
            })

            featureContext.setStyle(
                new ol.style.Style({
                    stroke: new ol.style.Stroke({
                        color: context[cc].displayColor,
                        width: 3
                    })
                })
            );

            var layerContext = new ol.layer.Vector({
                source: new ol.source.Vector({
                    features: [featureContext]
                })
            });
            map.addLayer(layerContext);

What I have done right now:

   map.on('singleclick', function(evt) {
        if (evt.dragging) {
          return;
        }
        var feature = map.forEachFeatureAtPixel(map.getEventPixel(evt.originalEvent), function(feature) {
            return feature;
        });
        if (feature) {
           popUp(feature);
        }
    });

But this will select everything on the polygon (area, etc.) and popup informations in the polygon.

Thanks for your help.

Answer 1

Not optimal but maybe if you draw the boundaries as a line (in addition to polygon) and only accept if feature is a line ? Also add an id in the properties of the line which point to the polygon. There must be some better ways ... but if you have only a few small polygons this is ok.