extlib/leaflet/src/handler/ScrollWheelZoom.js

   1 /*
   2  * L.Handler.ScrollWheelZoom is used internally by L.Map to enable mouse scroll wheel zooming on the map.
   3  */
   4
   5 L.Handler.ScrollWheelZoom = L.Handler.extend({
   6         enable: function() {
   7                 if (this._enabled) { return; }
   8                 L.DomEvent.addListener(this._map._container, 'mousewheel', this._onWheelScroll, this);
   9                 this._delta = 0;
  10                 this._enabled = true;
  11         },
  12
  13         disable: function() {
  14                 if (!this._enabled) { return; }
  15                 L.DomEvent.removeListener(this._map._container, 'mousewheel', this._onWheelScroll);
  16                 this._enabled = false;
  17         },
  18
  19         _onWheelScroll: function(e) {
  20                 this._delta += L.DomEvent.getWheelDelta(e);
  21                 this._lastMousePos = this._map.mouseEventToContainerPoint(e);
  22
  23                 clearTimeout(this._timer);
  24                 this._timer = setTimeout(L.Util.bind(this._performZoom, this), 50);
  25
  26                 L.DomEvent.preventDefault(e);
  27         },
  28
  29         _performZoom: function() {
  30                 var delta = Math.round(this._delta);
  31                 this._delta = 0;
  32
  33                 if (!delta) { return; }
  34
  35                 var center = this._getCenterForScrollWheelZoom(this._lastMousePos, delta),
  36                         zoom = this._map.getZoom() + delta;
  37
  38                 if (this._map._limitZoom(zoom) == this._map._zoom) { return; }
  39
  40                 this._map.setView(center, zoom);
  41         },
  42
  43         _getCenterForScrollWheelZoom: function(mousePos, delta) {
  44                 var centerPoint = this._map.getPixelBounds().getCenter(),
  45                         viewHalf = this._map.getSize().divideBy(2),
  46                         centerOffset = mousePos.subtract(viewHalf).multiplyBy(1 - Math.pow(2, -delta)),
  47                         newCenterPoint = centerPoint.add(centerOffset);
  48                 return this._map.unproject(newCenterPoint, this._map._zoom, true);
  49         }
  50 });