Merge pull request #754 from fs-webdev/master

Added a patch to help slow down the scroll devices that fire too fast…

src/openseadragon.js

@@ -255,6 +255,11 @@
   * @property {Boolean} [preserveImageSizeOnResize=false]
   *     Set to true to have the image size preserved when the viewer is resized. This requires autoResize=true (default).
   *
+  * @property {Number} [minScrollDeltaTime=50]
+  *     Number of milliseconds between canvas-scroll events. This value helps normalize the rate of canvas-scroll
+  *     events between different devices, causing the faster devices to slow down enough to make the zoom control
+  *     more manageable.
+  *
   * @property {Number} [pixelsPerWheelLine=40]
   *     For pixel-resolution scrolling devices, the number of pixels equal to one scroll line.
   *
@@ -1003,6 +1008,7 @@ if (typeof define === 'function' && define.amd) {
             pixelsPerWheelLine:     40,
             autoResize:             true,
             preserveImageSizeOnResize: false, // requires autoResize=true
+            minScrollDeltaTime:     50,
 
             //DEFAULT CONTROL SETTINGS
             showSequenceControl:     true,  //SEQUENCE

src/viewer.js

@@ -203,6 +203,8 @@ $.Viewer = function( options ) {
     this._loadQueue = [];
     this.currentOverlays = [];
 
+    this._lastScrollTime = $.now(); // variable used to help normalize the scroll event speed of different devices
+
     //Inherit some behaviors and properties
     $.EventSource.call( this );
 
@@ -604,7 +606,7 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
             var originalSuccess = options.success;
             options.success = function(event) {
                 successes++;
-                
+
                 // TODO: now that options has other things besides tileSource, the overlays
                 // should probably be at the options level, not the tileSource level.
                 if (options.tileSource.overlays) {
@@ -2738,44 +2740,57 @@ function onCanvasPinch( event ) {
 
 function onCanvasScroll( event ) {
     var gestureSettings,
-        factor;
+        factor,
+        thisScrollTime,
+        deltaScrollTime;
 
-    if ( !event.preventDefaultAction && this.viewport ) {
+    /* Certain scroll devices fire the scroll event way too fast so we are injecting a simple adjustment to keep things
-        gestureSettings = this.gestureSettingsByDeviceType( event.pointerType );
+     * partially normalized. If we have already fired an event within the last 'minScrollDelta' milliseconds we skip
-        if ( gestureSettings.scrollToZoom ) {
+     * this one and wait for the next event. */
-            factor = Math.pow( this.zoomPerScroll, event.scroll );
+    thisScrollTime = $.now();
-            this.viewport.zoomBy(
+    deltaScrollTime = thisScrollTime - this._lastScrollTime;
-                factor,
+    if (deltaScrollTime > this.minScrollDeltaTime) {
-                this.viewport.pointFromPixel( event.position, true )
+        this._lastScrollTime = thisScrollTime;
-            );
+
-            this.viewport.applyConstraints();
+        if ( !event.preventDefaultAction && this.viewport ) {
+            gestureSettings = this.gestureSettingsByDeviceType( event.pointerType );
+            if ( gestureSettings.scrollToZoom ) {
+                factor = Math.pow( this.zoomPerScroll, event.scroll );
+                this.viewport.zoomBy(
+                    factor,
+                    this.viewport.pointFromPixel( event.position, true )
+                );
+                this.viewport.applyConstraints();
+            }
+        }
+        /**
+         * Raised when a scroll event occurs on the {@link OpenSeadragon.Viewer#canvas} element (mouse wheel).
+         *
+         * @event canvas-scroll
+         * @memberof OpenSeadragon.Viewer
+         * @type {object}
+         * @property {OpenSeadragon.Viewer} eventSource - A reference to the Viewer which raised this event.
+         * @property {OpenSeadragon.MouseTracker} tracker - A reference to the MouseTracker which originated this event.
+         * @property {OpenSeadragon.Point} position - The position of the event relative to the tracked element.
+         * @property {Number} scroll - The scroll delta for the event.
+         * @property {Boolean} shift - True if the shift key was pressed during this event.
+         * @property {Object} originalEvent - The original DOM event.
+         * @property {?Object} userData - Arbitrary subscriber-defined object.
+         */
+        this.raiseEvent( 'canvas-scroll', {
+            tracker: event.eventSource,
+            position: event.position,
+            scroll: event.scroll,
+            shift: event.shift,
+            originalEvent: event.originalEvent
+        });
+        if (gestureSettings && gestureSettings.scrollToZoom) {
+            //cancels event
+            return false;
         }
     }
-    /**
+    else {
-     * Raised when a scroll event occurs on the {@link OpenSeadragon.Viewer#canvas} element (mouse wheel).
+        return false;   // We are swallowing this event
-     *
-     * @event canvas-scroll
-     * @memberof OpenSeadragon.Viewer
-     * @type {object}
-     * @property {OpenSeadragon.Viewer} eventSource - A reference to the Viewer which raised this event.
-     * @property {OpenSeadragon.MouseTracker} tracker - A reference to the MouseTracker which originated this event.
-     * @property {OpenSeadragon.Point} position - The position of the event relative to the tracked element.
-     * @property {Number} scroll - The scroll delta for the event.
-     * @property {Boolean} shift - True if the shift key was pressed during this event.
-     * @property {Object} originalEvent - The original DOM event.
-     * @property {?Object} userData - Arbitrary subscriber-defined object.
-     */
-    this.raiseEvent( 'canvas-scroll', {
-        tracker: event.eventSource,
-        position: event.position,
-        scroll: event.scroll,
-        shift: event.shift,
-        originalEvent: event.originalEvent
-    });
-
-    if (gestureSettings && gestureSettings.scrollToZoom) {
-        //cancels event
-        return false;
     }
 }