Flipping the direction of WheelEvent.deltaX/Y to follow standards

tools/dom/templates/html/impl/impl_WheelEvent.darttemplate

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 

[Andrei Mouravski, 2013/04/03 00:10:31]

Could you add some minimal dartdoc documentation? 

[blois, 2013/04/03 00:35:34]

Added some comments to the deltaX/deltaY members.

   factory WheelEvent(String type,
       {Window view, int deltaX: 0, int deltaY: 0,
       int detail: 0, int screenX: 0, int screenY: 0, int clientX: 0,
       int clientY: 0, int button: 0, bool canBubble: true,
       bool cancelable: true, bool ctrlKey: false, bool altKey: false,
       bool shiftKey: false, bool metaKey: false, EventTarget relatedTarget}) {
 
     if (view == null) {
       view = window;
     }
     var eventType = 'WheelEvent';
     if (Device.isFirefox) {
       eventType = 'MouseScrollEvents';
     }
     final event = document.$dom_createEvent(eventType);
 $if DART2JS
+    // If polyfilling, then flip these to match W3C wheel spec.

[Emily Fortuna, 2013/04/02 23:59:09]

Can you link to the w3c spec or (better) say which direction is positive
according to the spec here?

[blois, 2013/04/03 00:35:34]

Added link to the spec, but it doesn't actually specify which direction is
positive. Primary thing is that if we're flipping the values on the read-back,
then we should unflip them here so manually generated events are consistent.

IE10 and FF recently added support for the W3C events (though IE does not
publicize it properly, so we don't use it there). I was able to validate that
they are both consistent in their direction, so this adjusts the polyfills to be
consistent as well.

+    if (JS('bool', '#.deltaY === undefined', event)) {
+      deltaX = -deltaX;
+      deltaY = -deltaY;
+    }
     if (event._hasInitWheelEvent) {
       var modifiers = [];
       if (ctrlKey) {
         modifiers.push('Control');
       }
       if (altKey) {
         modifiers.push('Alt');
       }
       if (shiftKey) {
         modifiers.push('Shift');
@@ skipping 41 matching lines @@
 $!MEMBERS
 
 $if DART2JS
   @DomName('WheelEvent.deltaY')
   num get deltaY {
     if (JS('bool', '#.deltaY !== undefined', this)) {
       // W3C WheelEvent
       return this._deltaY;
     } else if (JS('bool', '#.wheelDelta !== undefined', this)) {
       // Chrome and IE
-      return this._wheelDelta;
+      return -this._wheelDelta;
     } else if (JS('bool', '#.detail !== undefined', this)) {
       // Firefox
 
       // Handle DOMMouseScroll case where it uses detail and the axis to
       // differentiate.
       if (JS('bool', '#.axis == MouseScrollEvent.VERTICAL_AXIS', this)) {
         var detail = this._detail;
         // Firefox is normally the number of lines to scale (normally 3)
         // so multiply it by 40 to get pixels to move, matching IE & WebKit.
         if (detail < 100) {
-          return detail * 40;
+          return -detail * 40;
         }
-        return detail;
+        return -detail;
       }
       return 0;
     }
     throw new UnsupportedError(
         'deltaY is not supported');
   }
 
   @DomName('WheelEvent.deltaX')
   num get deltaX {
     if (JS('bool', '#.deltaX !== undefined', this)) {
       // W3C WheelEvent
       return this._deltaX;
     } else if (JS('bool', '#.wheelDeltaX !== undefined', this)) {
       // Chrome
-      return this._wheelDeltaX;
+      return -this._wheelDeltaX;
     } else if (JS('bool', '#.detail !== undefined', this)) {
       // Firefox and IE.
       // IE will have detail set but will not set axis.
 
       // Handle DOMMouseScroll case where it uses detail and the axis to
       // differentiate.
       if (JS('bool', '#.axis !== undefined && '
         '#.axis == MouseScrollEvent.HORIZONTAL_AXIS', this, this)) {
         var detail = this._detail;
         // Firefox is normally the number of lines to scale (normally 3)
         // so multiply it by 40 to get pixels to move, matching IE & WebKit.
         if (detail < 100) {
-          return detail * 40;
+          return -detail * 40;
         }
-        return detail;
+        return -detail;
       }
       return 0;
     }
     throw new UnsupportedError(
         'deltaX is not supported');
   }
 
   @DomName('WheelEvent.deltaMode')
   int get deltaMode {
     if (JS('bool', '!!(#.deltaMode)', this)) {
@@ skipping 47 matching lines @@
       int button,
       EventTarget relatedTarget,
       String modifiersList,
       int deltaX,
       int deltaY,
       int deltaZ,
       int deltaMode) native;
 
 $else
   @DomName('WheelEvent.deltaX')
-  num get deltaX => $dom_wheelDeltaX;
+  num get deltaX => -$dom_wheelDeltaX;
   @DomName('WheelEvent.deltaY')
-  num get deltaY => $dom_wheelDeltaY;
+  num get deltaY => -$dom_wheelDeltaY;
 $endif
 }