fix rounding issue when delta is less than 0

Author: brandonaaron

jquery.mousewheel.js

@@ -64,7 +64,7 @@
 
 
     function handler(event) {
-        var orgEvent = event || window.event, args = [].slice.call( arguments, 1 ), delta = 0, deltaX = 0, deltaY = 0, absDelta = 0, absDeltaXY = 0;
+        var orgEvent = event || window.event, args = [].slice.call( arguments, 1 ), delta = 0, deltaX = 0, deltaY = 0, absDelta = 0, absDeltaXY = 0, fn;
         event = $.event.fix(orgEvent);
         event.type = "mousewheel";
 
@@ -86,14 +86,20 @@
         if ( orgEvent.wheelDeltaY !== undefined ) { deltaY = orgEvent.wheelDeltaY;      }
         if ( orgEvent.wheelDeltaX !== undefined ) { deltaX = orgEvent.wheelDeltaX * -1; }
 
+        // Look for lowest delta to normalize the delta values
         absDelta = Math.abs(delta);
         if ( !lowestDelta || absDelta < lowestDelta ) { lowestDelta = absDelta; }
-
         absDeltaXY = Math.max( Math.abs(deltaY), Math.abs(deltaX) );
         if ( !lowestDeltaXY || absDeltaXY < lowestDeltaXY ) { lowestDeltaXY = absDeltaXY; }
 
+        // Get a whole value for the deltas
+        fn = delta > 0 ? 'floor' : 'ceil';
+        delta  = Math[fn](delta/lowestDelta);
+        deltaX = Math[fn](deltaX/lowestDeltaXY);
+        deltaY = Math[fn](deltaY/lowestDeltaXY);
+
         // Add event and delta to the front of the arguments
-        args.unshift(event, Math.floor(delta/lowestDelta), Math.floor(deltaX/lowestDeltaXY), Math.floor(deltaY/lowestDeltaXY));
+        args.unshift(event, delta, deltaX, deltaY);
 
         return ($.event.dispatch || $.event.handle).apply(this, args);
     }