[NTP4] Auto-deletion of empty apps panes.

chrome/browser/resources/shared/js/cr/ui/card_slider.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 Card slider implementation. Allows you to create interactions
  * that have items that can slide left to right to reveal additional items.
  * Works by adding the necessary event handlers to a specific DOM structure
  * including a frame, container and cards.
  * - The frame defines the boundary of one item. Each card will be expanded to
@@ skipping 61 matching lines @@
      */
     this.touchHandler_ = new cr.ui.TouchHandler(this.container_);
   }
 
   /**
    * Events fired by the slider.
    * Events are fired at the container.
    */
   CardSlider.EventType = {
     // Fired when the user slides to another card.
-    CARD_CHANGED: 'cardSlider:card_changed'
+    CARD_CHANGED: 'cardSlider:card_changed',
+    CARD_CHANGE_ENDED: 'cardSlider:card_change_ended'
   };
 
 
   /**
    * The time to transition between cards when animating. Measured in ms.
    * @type {number}
    * @private
    * @const
    */
   CardSlider.TRANSITION_TIME_ = 200;
@@ skipping 32 matching lines @@
 
       this.updateCardWidths_();
 
       this.mouseWheelScrollAmount_ = 0;
       this.mouseWheelCardSelected_ = false;
       this.mouseWheelIsContinuous_ = false;
       this.scrollClearTimeout_ = null;
       this.frame_.addEventListener('mousewheel',
                                    this.onMouseWheel_.bind(this));
 
+      // Listen for the end of card movements (which is currently implemented
+      // with -webkit-transitions of -webkit-transforms.
+      this.container_.addEventListener('webkitTransitionEnd',
+          this.onWebkitTransitionEnd_.bind(this));
+
       // Also support touch events in case a touch screen happens to be
       // available.  Ideally we would support touch events whenever they
       // are fired, but for now restrict this extra code to when we know
       // we want to support touch input.
       if (cr.isTouchOptimized) {
         var TouchHandler = cr.ui.TouchHandler;
         this.container_.addEventListener(TouchHandler.EventType.TOUCH_START,
                                          this.onTouchStart_.bind(this));
         this.container_.addEventListener(TouchHandler.EventType.DRAG_START,
                                          this.onDragStart_.bind(this));
@@ skipping 145 matching lines @@
      * Resets the amount of horizontal scroll we've seen to 0. See
      * onMouseWheel_.
      * @private
      */
     clearMouseWheelScroll_: function() {
       this.mouseWheelScrollAmount_ = 0;
       this.mouseWheelCardSelected_ = false;
     },
 
     /**
+     * Handles the ends of -webkit-transitions on -webkit-transform (animated
+     * card switches).
+     * @param {Event} e The webkitTransitionEnd event.
+     * @private
+     */
+    onWebkitTransitionEnd_: function(e) {
+      // Ignore irrelevant transitions that might bubble up.
+      if (e.target !== this.container_ ||
+          e.propertyName != '-webkit-transform') {
+        return;
+      }
+      this.fireChangeEndEvent_();
+    },
+
+    /**
+     * Dispatches a simple event to tell subscribers we're done moving to the
+     * newly selected card.
+     * @private
+     */
+    fireChangeEndEvent_: function() {
+      var e = document.createEvent('Event');
+      e.initEvent(CardSlider.EventType.CARD_CHANGE_ENDED, true, true);
+      e.cardSlider = this;
+      this.container_.dispatchEvent(e);
+    },
+
+    /**
      * Selects a new card, ensuring that it is a valid index, transforming the
      * view and possibly calling the change card callback.
      * @param {number} newCardIndex Index of card to show.
      * @param {boolean=} opt_animate If true will animate transition from
      *     current position to new position.
      */
     selectCard: function(newCardIndex, opt_animate) {
       var previousCard = this.currentCardValue;
 
       var isChangingCard =
           !this.cards_[newCardIndex].classList.contains('selected-card');
 
       if (isChangingCard) {
-        previousCard.classList.remove('selected-card');
+        if (previousCard)
+          previousCard.classList.remove('selected-card');
         // If we have a new card index and it is valid then update the left
         // position and current card index.
         this.currentCard_ = newCardIndex;
         this.currentCardValue.classList.add('selected-card');
       }
 
-      this.transformToCurrentCard_(opt_animate);
+      var willTransitionHappen = this.transformToCurrentCard_(opt_animate);
 
       if (isChangingCard) {
         var event = document.createEvent('Event');
         event.initEvent(CardSlider.EventType.CARD_CHANGED, true, true);
         event.cardSlider = this;
         this.container_.dispatchEvent(event);
 
         // We also dispatch an event on the cards themselves.
         if (previousCard) {
           cr.dispatchSimpleEvent(previousCard, 'carddeselected',
                                  true, true);
         }
         cr.dispatchSimpleEvent(this.currentCardValue, 'cardselected',
                                true, true);
       }
+
+      // If we're not changing, animated, or transitioning, fire a
+      // CARD_CHANGE_ENDED event right away.
+      if (!isChangingCard || !opt_animate || !willTransitionHappen)
+        this.fireChangeEndEvent_();
     },
 
     /**
      * Selects a card from the stack. Passes through to selectCard.
      * @param {Node} newCard The card that should be selected.
      * @param {boolean=} opt_animate Whether to animate.
      */
     selectCardByValue: function(newCard, opt_animate) {
       var i = this.cards_.indexOf(newCard);
       assert(i != -1);
       this.selectCard(i, opt_animate);
     },
 
     /**
      * Centers the view on the card denoted by this.currentCard. Can either
      * animate to that card or snap to it.
      * @param {boolean=} opt_animate If true will animate transition from
      *     current position to new position.
+     * @return {boolean} Whether or not a transformation was necessary.
      * @private
      */
     transformToCurrentCard_: function(opt_animate) {
+      var prevLeft = this.currentLeft_;
       this.currentLeft_ = -this.cardWidth_ *
           (isRTL() ? this.cards_.length - this.currentCard - 1 :
                      this.currentCard);
 
+      // If there's no change, return something to let the caller no there won't
+      // be a transition occuring.
+      if (prevLeft == this.currentLeft_)
+        return false;
+
       // Animate to the current card, which will either transition if the
       // current card is new, or reset the existing card if we didn't drag
       // enough to change cards.
       var transition = '';
       if (opt_animate) {
         transition = '-webkit-transform ' + CardSlider.TRANSITION_TIME_ +
                      'ms ease-in-out';
       }
       this.container_.style.WebkitTransition = transition;
       this.translateTo_(this.currentLeft_);
+
+      return true;
     },
 
     /**
      * Moves the view to the specified position.
      * @param {number} x Horizontal position to move to.
      * @private
      */
     translateTo_: function(x) {
       // We use a webkitTransform to slide because this is GPU accelerated on
       // Chrome and iOS.  Once Chrome does GPU acceleration on the position
@@ skipping 74 matching lines @@
 
       // Ensure we're at a card bounary
       this.transformToCurrentCard_(true);
     },
   };
 
   return {
     CardSlider: CardSlider
   };
 });