Use a specialized new tab page in TOUCH_UI builds

chrome/browser/resources/touch_ntp/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
+ *   fill the width of the frame. This element is also overflow hidden so that
+ *   the additional items left / right do not trigger horizontal scrolling.
+ * - The container is what all the touch events are attached to. This element
+ *   will be expanded to be the width of all cards.
+ * - The cards are the individual viewable items. There should be one card for
+ *   each item in the list. Only one card will be visible at a time. Two cards
+ *   will be visible while you are transitioning between cards.
+ *
+ * This class is designed to work well on any hardware-accelerated touch device.
+ * It should still work on pre-hardware accelerated devices it just won't feel
+ * very good. It should also work well with a mouse.
+ */
+
+/**
+ * @constructor
+ * @param {!Element} frame The bounding rectangle that cards are visible in.
+ * @param {!Element} container The surrounding element that will have event
+ *     listeners attached to it.
+ * @param {!Array.<!Element>} cards The individual viewable cards.
+ * @param {number} currentCard The index of the card that is currently visible.
+ * @param {number} cardWidth The width of each card should have.
+ */
+function Slider(frame, container, cards, currentCard, cardWidth) {
+  /**
+   * @type {!Element}
+   * @private
+   */
+  this.frame_ = frame;
+
+  /**
+   * @type {!Element}
+   * @private
+   */
+  this.container_ = container;
+
+  /**
+   * @type {!Array.<!Element>}
+   * @private
+   */
+  this.cards_ = cards;
+
+  /**
+   * @type {number}
+   * @private
+   */
+  this.currentCard_ = currentCard;
+
+  /**
+   * @type {number}
+   * @private
+   */
+  this.cardWidth_ = cardWidth;
+
+  /**
+   * @type {!TouchHandler}
+   * @private
+   */
+  this.touchHandler_ = new TouchHandler(this.container_);
+}
+
+
+/**
+ * Events fired by the slider.
+ * Events are fired at the container.
+ */
+Slider.EventType = {
+  // Fired when the user slides to another card.
+  CARD_CHANGED: 'slider:card_changed'
+};
+
+
+/**
+ * The current left offset of the container relative to the frame.
+ * @type {number}
+ * @private
+ */
+Slider.prototype.currentLeft_ = 0;
+
+
+/**
+ * The time to transition between cards when animating. Measured in ms.
+ * @type {number}
+ * @private
+ */
+Slider.TRANSITION_TIME_ = 200;
+
+
+/**
+ * The minimum velocity required to transition cards if they did not drag past
+ * the halfway point between cards. Measured in pixels / ms.
+ * @type {number}
+ * @private
+ */
+Slider.TRANSITION_VELOCITY_THRESHOLD_ = 0.2;
+
+/**
+ * Initialize all elements and event handlers. Must call after construction and
+ * before usage.
+ */
+Slider.prototype.initialize = function() {
+  var view = this.container_.ownerDocument.defaultView;
+  assert(view.getComputedStyle(this.container_).display == '-webkit-box',
+      'Container should be display -webkit-box.');
+  assert(view.getComputedStyle(this.frame_).overflow == 'hidden',
+      'Frame should be overflow hidden.');
+  assert(view.getComputedStyle(this.container_).position == 'static',
+      'Container should be position static.');
+  for (var i = 0, card; card = this.cards_[i]; i++)
+    assert(view.getComputedStyle(card).position == 'static',
+        'Cards should be position static.');
+
+  this.updateCardWidths_();
+  this.transformToCurrentCard_();
+
+  this.container_.addEventListener(TouchHandler.EventType.TOUCH_START,
+                                   this.onTouchStart_.bind(this), false);
+  this.container_.addEventListener(TouchHandler.EventType.DRAG_START,
+                                   this.onDragStart_.bind(this), false);
+  this.container_.addEventListener(TouchHandler.EventType.DRAG_MOVE,
+                                   this.onDragMove_.bind(this), false);
+  this.container_.addEventListener(TouchHandler.EventType.DRAG_END,
+                                   this.onDragEnd_.bind(this), false);
+
+  this.touchHandler_.enable(/* opt_capture */ false);
+};
+
+
+/**
+ * Use in cases where the width of the frame has changed in order to update the
+ * width of cards. For example should be used when orientation changes in
+ * full width sliders.
+ * @param {number} newCardWidth Width all cards should have, in pixels.
+ */
+Slider.prototype.resize = function(newCardWidth) {
+  if (newCardWidth != this.cardWidth_) {
+    this.cardWidth_ = newCardWidth;
+
+    this.updateCardWidths_();
+
+    // Must upate the transform on the container to show the correct card.
+    this.transformToCurrentCard_();
+  }
+};
+
+
+/**
+ * Sets the cards used. Can be called more than once to switch card sets.
+ * @param {!Array.<!Element>} cards The individual viewable cards.
+ * @param {number} index Index of the card to in the new set of cards to
+ *     navigate to.
+ */
+Slider.prototype.setCards = function(cards, index) {
+  assert(index >= 0 && index < cards.length,
+      'Invalid index in Slider#setCards');
+  this.cards_ = cards;
+
+  this.updateCardWidths_();
+
+  // Jump to the given card index.
+  this.setCurrentCard(index);
+};
+
+
+/**
+ * Updates the width of each card.
+ * @private
+ */
+Slider.prototype.updateCardWidths_ = function() {
+  for (var i = 0, card; card = this.cards_[i]; i++)
+    card.style.width = this.cardWidth_ + 'px';
+};
+
+
+/**
+ * Returns the index of the current card.
+ * @return {number} index of the current card.
+ */
+Slider.prototype.getCurrentCard = function() {
+  return this.currentCard_;
+};
+
+/**
+ * Clear any transition that is in progress and enable dragging for the touch.
+ * @param {!CustomEvent} e The TouchHandler event.
+ * @private
+ */
+Slider.prototype.onTouchStart_ = function(e) {
+  this.container_.style.WebkitTransition = '';
+  e.detail.enableDrag = true;
+};
+
+
+/**
+ * Tell the TouchHandler that dragging is acceptable when the user begins by
+ * scrolling horizontally.
+ * @param {!CustomEvent} e The TouchHandler event.
+ * @private
+ */
+Slider.prototype.onDragStart_ = function(e) {
+  e.detail.enableDrag = Math.abs(e.detail.dragDeltaX) >
+      Math.abs(e.detail.dragDeltaY);
+};
+
+
+/**
+ * On each drag move event reposition the container appropriately so the cards
+ * look like they are sliding.
+ * @param {!CustomEvent} e The TouchHandler event.
+ * @private
+ */
+Slider.prototype.onDragMove_ = function(e) {
+  var deltaX = e.detail.dragDeltaX;
+  // If dragging beyond the first or last card then apply a backoff so the
+  // dragging feels stickier than usual.
+  if (!this.currentCard_ && deltaX > 0 ||
+      this.currentCard_ == (this.cards_.length - 1) && deltaX < 0) {
+    deltaX /= 2;
+  }
+  this.translateTo_(this.currentLeft_ + deltaX);
+};
+
+/**
+ * Moves the view to the specified position.
+ * @param {number} x Horizontal position to move to.
+ * @private
+ */
+Slider.prototype.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 fixed-layout
+  // elements we could simply set the element's position to fixed and modify
+  // 'left' instead.
+  this.container_.style.WebkitTransform = 'translate3d(' + x + 'px, 0, 0)';
+};
+
+/**
+ * On drag end events we may want to transition to another card, depending on
+ * the ending position of the drag and the velocity of the drag.
+ * @param {!CustomEvent} e The TouchHandler event.
+ * @private
+ */
+Slider.prototype.onDragEnd_ = function(e) {
+  var deltaX = e.detail.dragDeltaX;
+  var velocity = this.touchHandler_.getEndVelocity().x;
+  var newX = this.currentLeft_ + deltaX;
+  var newCardIndex = Math.round(-newX / this.cardWidth_);
+
+  if (newCardIndex == this.currentCard_ && Math.abs(velocity) >
+      Slider.TRANSITION_VELOCITY_THRESHOLD_) {
+    // If the drag wasn't far enough to change cards but the velocity was high
+    // enough to transition anyways.
+    // If the velocity is to the left (negative) then the user wishes to go
+    // right (card +1).
+    newCardIndex += velocity > 0 ? -1 : 1;
+  }
+
+  this.setCurrentCard(newCardIndex, /* animate */ true);
+};
+
+/**
+ * Cancel any current touch/slide as if we saw a touch end
+ */
+Slider.prototype.cancelTouch = function() {
+  // Stop listening to any current touch
+  this.touchHandler_.cancelTouch();
+
+  // Ensure we're at a card bounary
+  this.transformToCurrentCard_(true);
+};
+
+/**
+ * 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.
+ */
+Slider.prototype.setCurrentCard =
+    function(newCardIndex, opt_animate) {
+  var isChangingCard = newCardIndex >= 0 && newCardIndex < this.cards_.length &&
+      newCardIndex != this.currentCard_;
+  if (isChangingCard)
+    // If we have a new card index and it is valid then update the left position
+    // and current card index.
+    this.currentCard_ = newCardIndex;
+
+  this.transformToCurrentCard_(opt_animate);
+
+  if (isChangingCard) {
+    var event = document.createEvent('HTMLEvents');
+    event.initEvent(Slider.EventType.CARD_CHANGED, true, true);
+    event.sender = this;
+    this.container_.dispatchEvent(event);
+  }
+};
+
+/**
+ * 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.
+ * @private
+ */
+Slider.prototype.transformToCurrentCard_ = function(opt_animate) {
+  this.currentLeft_ = -this.currentCard_ * this.cardWidth_;
+
+  // 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 ' + Slider.TRANSITION_TIME_ +
+                   'ms ease-in-out';
+  }
+  this.container_.style.WebkitTransition = transition;
+  this.translateTo_(this.currentLeft_);
+};
+