added option to the MouseWheel handler to trigger up/down events only

when wheel is released. r=elemoine (closes #2345)


git-svn-id: http://svn.openlayers.org/trunk/openlayers@9799 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Control/Navigation.js

@@ -46,7 +46,14 @@ OpenLayers.Control.Navigation = OpenLayers.Class(OpenLayers.Control, {
      * APIProperty: zoomWheelEnabled
      * {Boolean} Whether the mousewheel should zoom the map
      */
-    zoomWheelEnabled: true, 
+    zoomWheelEnabled: true,
+    
+    /**
+     * Property: mouseWheelOptions
+     * {Object} Options passed to the MouseWheel control (only useful if
+     *     <zoomWheelEnabled> is set to true)
+     */
+    mouseWheelOptions: null,
 
     /**
      * APIProperty: handleRightClicks
@@ -159,7 +166,8 @@ OpenLayers.Control.Navigation = OpenLayers.Class(OpenLayers.Control, {
         this.zoomBox.draw();
         this.handlers.wheel = new OpenLayers.Handler.MouseWheel(
                                     this, {"up"  : this.wheelUp,
-                                           "down": this.wheelDown} );
+                                           "down": this.wheelDown},
+                                    this.mouseWheelOptions );
     },
 
     /**
@@ -192,8 +200,11 @@ OpenLayers.Control.Navigation = OpenLayers.Class(OpenLayers.Control, {
      * deltaZ - {Integer}
      */
     wheelChange: function(evt, deltaZ) {
+        var currentZoom = this.map.getZoom();
         var newZoom = this.map.getZoom() + deltaZ;
-        if (!this.map.isValidZoomLevel(newZoom)) {
+        newZoom = Math.max(newZoom, 0);
+        newZoom = Math.min(newZoom, this.map.getNumZoomLevels());
+        if (newZoom === currentZoom) {
             return;
         }
         var size    = this.map.getSize();
@@ -213,9 +224,10 @@ OpenLayers.Control.Navigation = OpenLayers.Class(OpenLayers.Control, {
      * 
      * Parameters:
      * evt - {Event}
+     * delta - {Integer}
      */
-    wheelUp: function(evt) {
-        this.wheelChange(evt, 1);
+    wheelUp: function(evt, delta) {
+        this.wheelChange(evt, delta || 1);
     },
 
     /** 
@@ -224,9 +236,10 @@ OpenLayers.Control.Navigation = OpenLayers.Class(OpenLayers.Control, {
      * 
      * Parameters:
      * evt - {Event}
+     * delta - {Integer}
      */
-    wheelDown: function(evt) {
-        this.wheelChange(evt, -1);
+    wheelDown: function(evt, delta) {
+        this.wheelChange(evt, delta || -1);
     },
     
     /**

lib/OpenLayers/Handler/MouseWheel.js

@@ -28,6 +28,23 @@ OpenLayers.Handler.MouseWheel = OpenLayers.Class(OpenLayers.Handler, {
      */
     mousePosition: null,
 
+    /**
+     * Property: interval
+     * {Integer} In order to increase server performance, an interval (in 
+     *     milliseconds) can be set to reduce the number of up/down events 
+     *     called. If set, a new up/down event will not be set until the 
+     *     interval has passed. 
+     *     Defaults to 0, meaning no interval. 
+     */
+    interval: 0,
+    
+    /**
+     * Property: delta
+     * {Integer} When interval is set, delta collects the mousewheel z-deltas
+     *     of the events that occur within the interval.
+     */
+    delta: 0,
+    
     /**
      * Constructor: OpenLayers.Handler.MouseWheel
      *
@@ -138,7 +155,31 @@ OpenLayers.Handler.MouseWheel = OpenLayers.Class(OpenLayers.Handler, {
         //
         if (!overScrollableDiv && overMapDiv) {
             if (overLayerDiv) {
-                this.wheelZoom(e);
+                var delta = 0;
+                if (!e) {
+                    e = window.event;
+                }
+                if (e.wheelDelta) {
+                    delta = e.wheelDelta/120; 
+                    if (window.opera && window.opera.version() < 9.2) {
+                        delta = -delta;
+                    }
+                } else if (e.detail) {
+                    delta = -e.detail / 3;
+                }
+                this.delta = this.delta + delta;
+
+                if(this.interval) {
+                    window.clearTimeout(this._timeoutId);
+                    this._timeoutId = window.setTimeout(
+                        OpenLayers.Function.bind(function(){
+                            this.wheelZoom(e);
+                        }, this),
+                        this.interval
+                    );
+                } else {
+                    this.wheelZoom(e);
+                }
             }
             OpenLayers.Event.stop(e);
         }
@@ -153,19 +194,9 @@ OpenLayers.Handler.MouseWheel = OpenLayers.Class(OpenLayers.Handler, {
      * e - {Event}
      */
     wheelZoom: function(e) {
+        var delta = this.delta;
+        this.delta = 0;
         
-        var delta = 0;
-        if (!e) {
-            e = window.event;
-        }
-        if (e.wheelDelta) {
-            delta = e.wheelDelta/120; 
-            if (window.opera && window.opera.version() < 9.2) {
-                delta = -delta;
-            }
-        } else if (e.detail) {
-            delta = -e.detail / 3;
-        }
         if (delta) {
             // add the mouse position to the event because mozilla has 
             // a bug with clientX and clientY (see