Normalizing .dropEffect across platforms (specifically Windows).

chrome/browser/resources/ntp4/tile_page.js

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('ntp4', function() {
   'use strict';
 
   // We can't pass the currently dragging tile via dataTransfer because of
   // http://crbug.com/31037
   var currentlyDraggingTile = null;
@@ skipping 140 matching lines @@
       setCurrentlyDraggingTile(null);
 
       // tilePage will be null if we've already been removed.
       if (this.tilePage)
         this.tilePage.positionTile_(this.index);
 
       // Take an appropriate action with the drag clone.
       if (this.landedOnTrash) {
         this.dragClone.classList.add('deleting');
       } else if (this.tilePage) {
-        if (this.tilePage.selected && e.dataTransfer.dropEffect != 'copy') {
+        // HACK(dbeam): Until we fix dropEffect to the correct behavior it will

[csilv, 2011/09/13 18:57:24]

Change this to a TODO comment instead.

[Dan Beam, 2011/09/13 22:19:13]

Done.

+        // differ on windows - crbug.com/39399.  That's why we use the custom
+        // .tilePage.lastDropEffect_ instead of e.dataTransfer.dropEffect.
+        if (this.tilePage.selected && this.tilePage.lastDropEffect_ != 'copy') {
           // The drag clone can still be hidden from the last drag move event.
           this.dragClone.hidden = false;
           // The tile's contents may have moved following the respositioning;
           // adjust for that.
           var contentDiffX = this.dragClone.firstChild.offsetLeft -
               this.firstChild.offsetLeft;
           var contentDiffY = this.dragClone.firstChild.offsetTop -
               this.firstChild.offsetTop;
           this.dragClone.style.left = (this.gridX + this.parentNode.offsetLeft -
               contentDiffX) + 'px';
@@ skipping 748 matching lines @@
      * @param {Event} e A mouseover event for the drag over.
      */
     doDragOver: function(e) {
       e.preventDefault();
 
       this.setDropEffect(e.dataTransfer);
       var newDragIndex = this.getWouldBeIndexForPoint_(e.pageX, e.pageY);
       if (newDragIndex < 0 || newDragIndex >= this.tileElements_.length)
         newDragIndex = this.dragItemIndex_;
       this.updateDropIndicator_(newDragIndex);
+
+      this.lastDropEffect_ = e.dataTransfer.dropEffect;
     },
 
     /**
+     * Normalizing dropEffect until all platform's implementations agree.  Right
+     * now Windows resets the dropEffect on a 'drop' back to 'copy' (and
+     * disregards the previous state), so we're making a temporary shim to keep
+     * our own state for now based on each dragover.
+     */
+    lastDropEffect_: null,

[csilv, 2011/09/13 18:57:24]

Is it necessary to do this? (ie, wont the default value of undefined work?)

[Dan Beam, 2011/09/13 22:19:13]

Done.

+
+    /**
      * Performs all actions necessary when the user completes a drop.
      * @param {Event} e A mouseover event for the drag drop.
      */
     doDrop: function(e) {
       e.stopPropagation();
 
       var index = this.currentDropIndex_;
       // Only change data if this was not a 'null drag'.
       if (!((index == this.dragItemIndex_) && this.withinPageDrag_)) {
         var adjustedIndex = this.currentDropIndex_ +
@@ skipping 118 matching lines @@
     setDropEffect: function(dataTransfer) {
       assert(false);
     },
   };
 
   return {
     getCurrentlyDraggingTile: getCurrentlyDraggingTile,
     TilePage: TilePage,
   };
 });