Add a cumulative mode in MouseWheel handler. r=ahocevar (closes #2450)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@10002 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

examples/mousewheel-interval.html

@@ -6,6 +6,13 @@
     <script src="../lib/OpenLayers.js"></script>
     <script type="text/javascript">
         var map, layer;
+
+        function setCumulative() {
+            var nav = map.getControlsByClass("OpenLayers.Control.Navigation")[0];
+            var cumulative = document.getElementById("cumulative");
+            nav.handlers.wheel.cumulative = cumulative.checked;
+        }
+
         function init(){
             map = new OpenLayers.Map( 'map', {controls: [
                 new OpenLayers.Control.Navigation(
@@ -38,6 +45,13 @@
         spin the mousewheel, no request will be sent to the server. Instead,
         the zoomlevel delta will be recorded. After a delay (in this example
         100ms), a zoom action with the cumulated delta will be performed.</p>
+        <div>
+          <input id="cumulative" type="checkbox" checked="checked"
+                 onchange="setCumulative()"/>
+          <label for="cumulative">Cumulative mode. If this mode is deactivated, 
+            only one zoom event will be performed after the delay.</label>
+        </div>
+
     </div>
   </body>
 </html>

lib/OpenLayers/Handler/MouseWheel.js

@@ -42,9 +42,18 @@ OpenLayers.Handler.MouseWheel = OpenLayers.Class(OpenLayers.Handler, {
      * Property: delta
      * {Integer} When interval is set, delta collects the mousewheel z-deltas
      *     of the events that occur within the interval.
+     *      See also the cumulative option
      */
     delta: 0,
     
+    /**
+     * Property: cumulative
+     * {Boolean} When interval is set: true to collect all the mousewheel 
+     *     z-deltas, false to only record the delta direction (positive or
+     *     negative)
+     */
+    cumulative: true,
+
     /**
      * Constructor: OpenLayers.Handler.MouseWheel
      *
@@ -216,9 +225,9 @@ OpenLayers.Handler.MouseWheel = OpenLayers.Class(OpenLayers.Handler, {
                 );
             }
             if (delta < 0) {
-               this.callback("down", [e, delta]);
+                this.callback("down", [e, this.cumulative ? delta : -1]);
             } else {
-               this.callback("up", [e, delta]);
+                this.callback("up", [e, this.cumulative ? delta : 1]);
             }
         }
     },

tests/Handler/MouseWheel.html

@@ -114,8 +114,38 @@
         t.delay_call(1, function() {
             t.eq(deltaZ, 2, "Multiple scroll actions triggered one event when interval is set");
         });
+    }
 
+    function test_Handler_MouseWheel_cumulative(t) {
+        t.plan(1);
 
+        var deltaUp = 0;
+        var callbacks = {
+            up: function(evt, delta) {
+                deltaUp += delta;
+            }
+        };
+
+        var map = new OpenLayers.Map('map');
+        map.addLayer(new OpenLayers.Layer.WMS("","",{}));
+        map.zoomToMaxExtent();
+        var control = new OpenLayers.Control({});
+        map.addControl(control);
+        var handler = new OpenLayers.Handler.MouseWheel(control, callbacks, {
+            interval: 150,
+            cumulative: false    
+        });
+
+        var delta = 120;
+        // generate 20 scroll up in non cumulative mode
+        if (window.opera && window.opera.version() < 9.2)  delta = -delta;
+        for (var i=0; i < 20; i++) {
+            handler.onWheelEvent({'target':map.layers[0].div, wheelDelta: delta});
+        }
+        
+        t.delay_call(1, function() {
+            t.eq(deltaUp, 1, "Non cumulative mode works");
+        });
     }
 
     function test_Handler_MouseWheel_deactivate(t) {