Skip to content

Kinetic layer on top of Openlayers

I developed a canvas visualization of OpenStreetMaps by means of miscellaneous scripts and rendering algorithms from the internet. On top of this I have a Kinetic Stage which draws custom objects which cannot be drawn by the functionality of Openlayers.

Openlayers provides many functions which I want to use and therefore I’m trying to switch over to this framework. I’m currently stuck with the event propagation, because I don’t know how to propagate an event to Openlayers.

index.html

<div id="canvasdiv">
  <div id="KineticDiv"> </div>
  <div id="OLMapDiv"> </div>
</div>

style.css

#KineticDiv {
  position: absolute;
  z-index: 1000;
}
#OLMapDiv {
  position: absolute;
  width: 1000px;
  height: 600px;
  z-index: 0;
}

ol.js

function OpenLayersMap(divname) {
  var osmLayer = new OpenLayers.Layer.OSM("Open Street Maps",
    ["http://a.tile.openstreetmap.org/${z}/${x}/${y}.png",
     "http://b.tile.openstreetmap.org/${z}/${x}/${y}.png",
     "http://c.tile.openstreetmap.org/${z}/${x}/${y}.png"]);
                                        ]);
  var gmLayer = new OpenLayers.Layer.Google("Google Maps");
  var proj = new OpenLayers.Projection("EPSG:4326");

  OpenLayers.ImgPath = "/static/img/";

  this.map = new OpenLayers.Map({
    div: divname,
    allOverlays: false,
    theme: null,
    controls: [
      new OpenLayers.Control.Attribution(),
      new OpenLayers.Control.Navigation(),
      new OpenLayers.Control.LayerSwitcher(),
      new OpenLayers.Control.PanZoomBar(),
      new OpenLayers.Control.ScaleLine(),
      new OpenLayers.Control.MousePosition({
        displayProjection: proj
      }),
      new OpenLayers.Control.KeyboardDefaults()
      ]
  });
  this.map.addLayers([osmLayer, gmLayer]);
  this.map.setCenter(
    new OpenLayers.LonLat(8.56, 50).transform(proj, this.map.getProjectionObject()), 10
  );
}

OpenLayersMap.prototype = {
  constructor: OpenLayersMap
}

main.js

function main() {
  var self = this;
  this.olmap = new OpenLayersMap("OLMapDiv");
  this.kinetic = new KineticStage("KineticDiv");

  $("div#canvasdiv").bind("mouseout", function(event){
// TODO self.olmap.mouseOut(event);
  }).bind("mouseup", function(event){
// TODO self.olmap.mouseUp(event);
  }).bind("mousedown", function(event){
// TODO self.olmap.mouseDown(event);
  }).bind("mousewheel", function(event, delta){
// TODO self.olmap.mouseWheel(event, delta);
  }).bind("touchmove", function(event){
// TODO self.olmap.touchMove(event);
  }).bind("touchstart", function(event){
// TODO self.olmap.touchStart(event);
  }).bind("touchend", function(event){
// TODO self.olmap.touchEnd(event);
  });
}

Due to a higher z-index of the Kinetic Stage the event is recognized there. The event propagation is only stopped if a Kinetic Shape is hit!

Is there any suitable method in Openlayers which accepts events? (I found OpenLayers.Events.triggerEvent, but I didn’t succeed with it)

Answer

I came up with a solution which is almost satisfying. Only a few events have to be handled by the user. Replacing the TODO’s with

self.olmap.map.events.handleBrowserEvent(event);

enables the drag&drop function on the map. Here is an example how to handle the mousewheel event:

// main.js
$("div#canvasdiv").bind("mousewheel", function(event, delta){
   self.olmap.zoom(event, delta);
})

// ol.js
zoom : function(event, delta) {
    if(this.zoomExpireTime && this.zoomExpireTime == 0) {
        this.zoomExpireTime = event.timeStamp - 1;
    }
    if(this.zoomExpireTime < event.timeStamp) {
        this.map.zoomTo(this.map.getZoom() + delta);
        this.zoomExpireTime = event.timeStamp + 500;
    }
}

The controls of OpenLayers cannot be used, because they only react on click events and not on mousedown ones. I tried to convert the mousedown event to a click one, but then the drag&drop didn’t work anymore. Thus, I did a workaround which raises only the controls to the top as follows:

var z = parseInt($("div#KineticDiv").css("z-index")) + 100;
$("div[id=OpenLayers\.Control\.LayerSwitcher_8]").css("z-index", z);
$("div[id=OpenLayers\.Control\.LayerSwitcher_8]").appendTo($("div#canvasdiv"));
$("div[id=OpenLayers\.Control\.PanZoomBar_9]").css("z-index", z);
$("div[id=OpenLayers\.Control\.PanZoomBar_9]").appendTo($("div#canvasdiv"));

So this is my first scratch solution, but I think there is potential to improve it …