[Aura] Initial app list webui.

chrome/browser/resources/ntp4/drag_wrapper.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.
-
-/**
- * @fileoverview DragWrapper
- * A class for simplifying HTML5 drag and drop. Classes should use this to
- * handle the nitty gritty of nested drag enters and leaves.
- */
-var DragWrapper = (function() {
-  /**
-   * Creates a DragWrapper which listens for drag target events on |target| and
-   * delegates event handling to |handler|. The |handler| must implement:
-   *   shouldAcceptDrag
-   *   doDragEnter
-   *   doDragLeave
-   *   doDragOver
-   *   doDrop
-   */
-  function DragWrapper(target, handler) {
-    this.initialize(target, handler);
-  }
-
-  DragWrapper.prototype = {
-    initialize: function(target, handler) {
-      target.addEventListener('dragenter',
-                              this.onDragEnter_.bind(this));
-      target.addEventListener('dragover', this.onDragOver_.bind(this));
-      target.addEventListener('drop', this.onDrop_.bind(this));
-      target.addEventListener('dragleave', this.onDragLeave_.bind(this));
-
-      this.target_ = target;
-      this.handler_ = handler;
-    },
-
-    /**
-     * The number of un-paired dragenter events that have fired on |this|. This
-     * is incremented by |onDragEnter_| and decremented by |onDragLeave_|. This
-     * is necessary because dragging over child widgets will fire additional
-     * enter and leave events on |this|. A non-zero value does not necessarily
-     * indicate that |isCurrentDragTarget()| is true.
-     * @type {number}
-     * @private
-     */
-    dragEnters_: 0,
-
-    /**
-     * Whether the tile page is currently being dragged over with data it can
-     * accept.
-     * @type {boolean}
-     */
-    get isCurrentDragTarget() {
-      return this.target_.classList.contains('drag-target');
-    },
-
-    /**
-     * Handler for dragenter events fired on |target_|.
-     * @param {Event} e A MouseEvent for the drag.
-     * @private
-     */
-    onDragEnter_: function(e) {
-      if (++this.dragEnters_ == 1) {
-        if (this.handler_.shouldAcceptDrag(e)) {
-          this.target_.classList.add('drag-target');
-          this.handler_.doDragEnter(e);
-        }
-      } else {
-        // Sometimes we'll get an enter event over a child element without an
-        // over event following it. In this case we have to still call the
-        // drag over handler so that we make the necessary updates (one visible
-        // symptom of not doing this is that the cursor's drag state will
-        // flicker during drags).
-        this.onDragOver_(e);
-      }
-    },
-
-    /**
-     * Thunk for dragover events fired on |target_|.
-     * @param {Event} e A MouseEvent for the drag.
-     * @private
-     */
-    onDragOver_: function(e) {
-      if (!this.target_.classList.contains('drag-target'))
-        return;
-      this.handler_.doDragOver(e);
-    },
-
-    /**
-     * Thunk for drop events fired on |target_|.
-     * @param {Event} e A MouseEvent for the drag.
-     * @private
-     */
-    onDrop_: function(e) {
-      this.dragEnters_ = 0;
-      if (!this.target_.classList.contains('drag-target'))
-        return;
-      this.target_.classList.remove('drag-target');
-      this.handler_.doDrop(e);
-    },
-
-    /**
-     * Thunk for dragleave events fired on |target_|.
-     * @param {Event} e A MouseEvent for the drag.
-     * @private
-     */
-    onDragLeave_: function(e) {
-      if (--this.dragEnters_ > 0)
-        return;
-
-      this.target_.classList.remove('drag-target');
-      this.handler_.doDragLeave(e);
-    },
-  };
-
-  return DragWrapper;
-})();