Change the style of the draw overlay, if the cursor is snapped an other object

Question

i´ve got a drawing interaction to draw points. It is only allowed to draw these points if the boundary of features of an other source are snapped. Now, i the overlay feature has to change his own style, if the other features boundary is snapped.

var snapCondition = function(evt){
    var features = [];
    mapEntry.forEachFeatureAtPixel(evt.pixel, function(feature, layer) {
        if(layer != null && layer.get('name') === 'specialLayerName') {
            features.push(feature);
        }
    });
    if(features.length  === 1 ) {
        return checkBoundary(features[0], evt.coordinate);
    } else {
        return false;
    };
};

var checkBoundary = function(feature, coords) {
    var geom = feature.getGeometry();
    var closestPoint = geom.getClosestPoint(coords);
    console.log(closestPoint);
    console.log(coords)
    if((closestPoint[0] === coords[0]) && (closestPoint[1] === coords[1])) {
        return true;
    }
    return false;
} 
var drawBuildingEntry = new ol.interaction.Draw({
  source: buildingEntrySource,
  type: 'Point',
  condition: snapCondition,
  style: new ol.style.Style({
    image: new ol.style.Circle({
      radius: 7,
      fill: new ol.style.Fill({
        color: entryDrawColor,
      }),
      stroke: new ol.style.Stroke({
        color: 'white',
        width: 3
      })
    })
  })
});

The code above is working, but i´ve got the problems by changing the style. I tested the following code:

 mapEntry.on("pointermove", function (event) {
    var features = [];
    mapEntry.forEachFeatureAtPixel(event.pixel, function(feature, layer) {
        if(layer != null && layer.get('name') === 'specialLayerName') {
            features.push(feature);
        }
    });
    if(features.length  === 1 ) {
        console.log(checkBoundary(features[0], event.coordinate));
        if(checkBoundary(features[0], event.coordinate) === true) {
            entryDrawColor = '#40FF00'
        } else { 
            entryDrawColor = '#FF0000'; 
        };
    } else {
        entryDrawColor = '#FF0000'; 
    };});

The console.log of checkBoundary is even false, because the event coordinates, are the coordinates befor the overlay element is snapped. best regards Tim

Answer 1

The snap interaction doesn't change the pointer position, but it changes what is reported to the draw interaction, so you will probably need to test in a style function for the draw

  style: function(feature) {
    var entryDrawColor = '#FF0000';
    var geometry = feature.getGeometry();
    if (geometry.getType() = 'Point') {
      var coordinates = geometry.getCoordinates();
      var pixel = getPixelFromCoordinate(coordinate);

      ...

    }
    return new ol.style.Style({
      image: new ol.style.Circle({
        radius: 7,
        fill: new ol.style.Fill({
          color: entryDrawColor,
        }),
        stroke: new ol.style.Stroke({
          color: 'white',
          width: 3
        })
      })
    })
  }