Javascript
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// Copyright (c) 2012 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.
*/
// Use an anonymous function to enable strict mode just for this file (which
// will be concatenated with other files when embedded in Chrome
cr.define('cr.ui', function() {
'use strict';
/**
* @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 {number} cardWidth The width of each card should have.
*/
function CardSlider(frame, container, cardWidth) {
/**
* @type {!Element}
* @private
*/
this.frame_ = frame;
/**
* @type {!Element}
* @private
*/
this.container_ = container;
/**
* Array of card elements.
* @type {!Array.<!Element>}
* @private
*/
this.cards_ = [];
/**
* Index of currently shown card.
* @type {number}
* @private
*/
this.currentCard_ = -1;
/**
* @type {number}
* @private
*/
this.cardWidth_ = cardWidth;
/**
* @type {!cr.ui.TouchHandler}
* @private
*/
this.touchHandler_ = new cr.ui.TouchHandler(this.container_);
}
/**
* The time to transition between cards when animating. Measured in ms.
* @type {number}
* @private
* @const
*/
CardSlider.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
* @const
*/
CardSlider.TRANSITION_VELOCITY_THRESHOLD_ = 0.2;
CardSlider.prototype = {
/**
* The current left offset of the container relative to the frame.
* @type {number}
* @private
*/
currentLeft_: 0,
/**
* Initialize all elements and event handlers. Must call after construction
* and before usage.
* @param {boolean} ignoreMouseWheelEvents If true, horizontal mouse wheel
* events will be ignored, rather than flipping between pages.
*/
initialize: function(ignoreMouseWheelEvents) {
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.');
this.updateCardWidths_();
this.mouseWheelScrollAmount_ = 0;
this.mouseWheelCardSelected_ = false;
this.mouseWheelIsContinuous_ = false;
this.scrollClearTimeout_ = null;
if (!ignoreMouseWheelEvents) {
this.frame_.addEventListener('mousewheel',
this.onMouseWheel_.bind(this));
}
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));
this.container_.addEventListener(TouchHandler.EventType.DRAG_MOVE,
this.onDragMove_.bind(this));
this.container_.addEventListener(TouchHandler.EventType.DRAG_END,
this.onDragEnd_.bind(this));
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.
*/
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.
*/
setCards: function(cards, index) {
assert(index >= 0 && index < cards.length,
'Invalid index in CardSlider#setCards');
this.cards_ = cards;
this.updateCardWidths_();
// Jump to the given card index.
this.selectCard(index);
},
/**
* Updates the width of each card.
* @private
*/
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.
*/
get currentCard() {
return this.currentCard_;
},
/**
* Allows setting the current card index.
* @param {number} index A new index to set the current index to.
* @return {number} The new index after having been set.
*/
set currentCard(index) {
return (this.currentCard_ = index);
},
/**
* Returns the number of cards.
* @return {number} number of cards.
*/
get cardCount() {
return this.cards_.length;
},
/**
* Returns the current card itself.
* @return {!Element} the currently shown card.
*/
get currentCardValue() {
return this.cards_[this.currentCard_];
},
/**
* Returns the frame holding the cards.
* @return {Element} The frame used to position the cards.
*/
get frame() {
return this.frame_;
},
/**
* Handle horizontal scrolls to flip between pages.
* @private
*/
onMouseWheel_: function(e) {
if (e.wheelDeltaX == 0)
return;
// Continuous devices such as an Apple Touchpad or Apple MagicMouse will
// send arbitrary delta values. Conversly, standard mousewheels will
// send delta values in increments of 120. (There is of course a small
// chance we mistake a continuous device for a non-continuous device.
// Unfortunately there isn't a better way to do this until real touch
// events are available to desktop clients.)
var DISCRETE_DELTA = 120;
if (e.wheelDeltaX % DISCRETE_DELTA)
this.mouseWheelIsContinuous_ = true;
if (this.mouseWheelIsContinuous_) {
// For continuous devices, detect a page swipe when the accumulated
// delta matches a pre-defined threshhold. After changing the page,
// ignore wheel events for a short time before repeating this process.
if (this.mouseWheelCardSelected_) return;
this.mouseWheelScrollAmount_ += e.wheelDeltaX;
if (Math.abs(this.mouseWheelScrollAmount_) >= 600) {
var pagesToScroll = this.mouseWheelScrollAmount_ > 0 ? 1 : -1;
if (!isRTL())
pagesToScroll *= -1;
var newCardIndex = this.currentCard + pagesToScroll;
newCardIndex = Math.min(this.cards_.length - 1,
Math.max(0, newCardIndex));
this.selectCard(newCardIndex, true);
this.mouseWheelCardSelected_ = true;
}
} else {
// For discrete devices, consider each wheel tick a page change.
var pagesToScroll = e.wheelDeltaX / DISCRETE_DELTA;
if (!isRTL())
pagesToScroll *= -1;
var newCardIndex = this.currentCard + pagesToScroll;
newCardIndex = Math.min(this.cards_.length - 1,
Math.max(0, newCardIndex));
this.selectCard(newCardIndex, true);
}
// We got a mouse wheel event, so cancel any pending scroll wheel timeout.
if (this.scrollClearTimeout_ != null)
clearTimeout(this.scrollClearTimeout_);
// If we didn't use up all the scroll, hold onto it for a little bit, but
// drop it after a delay.
if (this.mouseWheelScrollAmount_ != 0) {
this.scrollClearTimeout_ =
setTimeout(this.clearMouseWheelScroll_.bind(this), 500);
}
},
/**
* 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.fireChangeEndedEvent_(true);
},
/**
* Dispatches a simple event to tell subscribers we're done moving to the
* newly selected card.
* @param {boolean} wasAnimated whether or not the change was animated.
* @private
*/
fireChangeEndedEvent_: function(wasAnimated) {
var e = document.createEvent('Event');
e.initEvent('cardSlider:card_change_ended', true, true);
e.cardSlider = this;
e.changedTo = this.currentCard_;
e.wasAnimated = wasAnimated;
this.container_.dispatchEvent(e);
},
/**
* Add a card to the card slider at a particular index. If the card being
* added is inserted in front of the current card, cardSlider.currentCard
* will be adjusted accordingly (to current card + 1).
* @param {!Node} card A card that will be added to the card slider.
* @param {number} index An index at which the given |card| should be
* inserted. Must be positive and less than the number of cards.
*/
addCardAtIndex: function(card, index) {
assert(card instanceof Node, '|card| isn\'t a Node');
this.assertValidIndex_(index);
this.cards_ = Array.prototype.concat.call(
this.cards_.slice(0, index), card, this.cards_.slice(index));
if (this.currentCard_ == -1)
this.currentCard_ = 0;
else if (index <= this.currentCard_)
this.selectCard(this.currentCard_ + 1, false, true, true);
this.fireAddedEvent_(card, index);
},
/**
* Append a card to the end of the list.
* @param {!Node} card A card to add at the end of the card slider.
*/
appendCard: function(card) {
assert(card instanceof Node, '|card| isn\'t a Node');
this.cards_.push(card);
this.fireAddedEvent_(card, this.cards_.length - 1);
},
/**
* Dispatches a simple event to tell interested subscribers that a card was
* added to this card slider.
* @param {Node} card The recently added card.
* @param {number} index The position of the newly added card.
* @private
*/
fireAddedEvent_: function(card, index) {
this.assertValidIndex_(index);
var e = document.createEvent('Event');
e.initEvent('cardSlider:card_added', true, true);
e.addedIndex = index;
e.addedCard = card;
this.container_.dispatchEvent(e);
},
/**
* Removes a card by index from the card slider. If the card to be removed
* is the current card or in front of the current card, the current card
* will be updated (to current card - 1).
* @param {!Node} card A card to be removed.
*/
removeCard: function(card) {
assert(card instanceof Node, '|card| isn\'t a Node');
this.removeCardAtIndex(this.cards_.indexOf(card));
},
/**
* Removes a card by index from the card slider. If the card to be removed
* is the current card or in front of the current card, the current card
* will be updated (to current card - 1).
* @param {number} index The index of the tile that should be removed.
*/
removeCardAtIndex: function(index) {
this.assertValidIndex_(index);
var removed = this.cards_.splice(index, 1).pop();
if (this.cards_.length == 0)
this.currentCard_ = -1;
else if (index < this.currentCard_)
this.selectCard(this.currentCard_ - 1, false, true);
this.fireRemovedEvent_(removed, index);
},
/**
* Dispatches a cardSlider:card_removed event so interested subscribers know
* when a card was removed from this card slider.
* @param {Node} card The recently removed card.
* @param {number} index The index of the card before it was removed.
* @private
*/
fireRemovedEvent_: function(card, index) {
var e = document.createEvent('Event');
e.initEvent('cardSlider:card_removed', true, true);
e.removedCard = card;
e.removedIndex = index;
this.container_.dispatchEvent(e);
},
/**
* Checks the the given |index| exists in this.cards_.
* @param {number} index An index to check.
* @private
*/
assertValidIndex_: function(index) {
assert(index >= 0 && index < this.cards_.length);
},
/**
* 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.
* @param {boolean=} opt_dontNotify If true, don't tell subscribers that
* we've changed cards.
* @param {boolean=} opt_forceChange If true, ignore if the card already
* selected.
*/
selectCard: function(newCardIndex,
opt_animate,
opt_dontNotify,
opt_forceChange) {
this.assertValidIndex_(newCardIndex);
var previousCard = this.currentCardValue;
var isChangingCard =
!this.cards_[newCardIndex].classList.contains('selected-card');
if (typeof opt_forceChange != 'undefined' && opt_forceChange)
isChangingCard = true;
if (isChangingCard) {
if (previousCard)
previousCard.classList.remove('selected-card');
this.currentCard_ = newCardIndex;
this.currentCardValue.classList.add('selected-card');
}
var willTransitionHappen = this.transformToCurrentCard_(opt_animate);
if (isChangingCard && !opt_dontNotify) {
var event = document.createEvent('Event');
event.initEvent('cardSlider:card_changed', true, true);
event.cardSlider = this;
event.wasAnimated = !!opt_animate;
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
// cardSlider:card_change_ended event right away.
if ((!isChangingCard || !opt_animate || !willTransitionHappen) &&
!opt_dontNotify) {
this.fireChangeEndedEvent_(false);
}
},
/**
* 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 know 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
// 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)';
},
/* Touch ******************************************************************/
/**
* Clear any transition that is in progress and enable dragging for the
* touch.
* @param {!cr.ui.TouchHandler.Event} e The TouchHandler event.
* @private
*/
onTouchStart_: function(e) {
this.container_.style.WebkitTransition = '';
e.enableDrag = true;
},
/**
* Tell the TouchHandler that dragging is acceptable when the user begins by
* scrolling horizontally.
* @param {!cr.ui.TouchHandler.Event} e The TouchHandler event.
* @private
*/
onDragStart_: function(e) {
e.enableDrag = Math.abs(e.dragDeltaX) > Math.abs(e.dragDeltaY);
},
/**
* On each drag move event reposition the container appropriately so the
* cards look like they are sliding.
* @param {!cr.ui.TouchHandler.Event} e The TouchHandler event.
* @private
*/
onDragMove_: function(e) {
var deltaX = e.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);
},
/**
* 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 {!cr.ui.TouchHandler.Event} e The TouchHandler event.
* @private
*/
onDragEnd_: function(e) {
var deltaX = e.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) >
CardSlider.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.selectCard(newCardIndex, /* animate */ true);
},
/**
* Cancel any current touch/slide as if we saw a touch end
*/
cancelTouch: function() {
// Stop listening to any current touch
this.touchHandler_.cancelTouch();
// Ensure we're at a card bounary
this.transformToCurrentCard_(true);
},
};
return {
CardSlider: CardSlider
};
});