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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 Page switcher
* This is the class for the left and right navigation arrows that switch
* between pages.
*/
cr.define('ntp', function() {
function PageSwitcher() {
}
PageSwitcher.template = {
__proto__: HTMLButtonElement.prototype,
decorate: function(el) {
el.__proto__ = PageSwitcher.template;
el.addEventListener('click', el.activate_);
el.direction_ = el.id == 'page-switcher-start' ? -1 : 1;
el.dragWrapper_ = new cr.ui.DragWrapper(el, el);
},
/**
* Activate the switcher (go to the next card).
* @private
*/
activate_: function() {
ntp.getCardSlider().selectCard(this.nextCardIndex_(), true);
},
/**
* Calculate the index of the card that this button will switch to.
* @private
*/
nextCardIndex_: function() {
var cardSlider = ntp.getCardSlider();
var index = cardSlider.currentCard + this.direction_;
var numCards = cardSlider.cardCount - 1;
return Math.max(0, Math.min(index, numCards));
},
/**
* Update the accessible label attribute of this button, based on the
* current position in the card slider and the names of the cards.
* @param {NodeList} dots The dot elements which display the names of the
* cards.
*/
updateButtonAccessibleLabel: function(dots) {
var currentIndex = ntp.getCardSlider().currentCard;
var nextCardIndex = this.nextCardIndex_();
if (nextCardIndex == currentIndex) {
this.setAttribute('aria-label', ''); // No next card.
return;
}
var currentDot = dots[currentIndex];
var nextDot = dots[nextCardIndex];
if (!currentDot || !nextDot) {
this.setAttribute('aria-label', ''); // Dots not initialised yet.
return;
}
var currentPageTitle = currentDot.displayTitle;
var nextPageTitle = nextDot.displayTitle;
var msgName = (currentPageTitle == nextPageTitle) ?
'page_switcher_same_title' : 'page_switcher_change_title';
var ariaLabel = loadTimeData.getStringF(msgName, nextPageTitle);
this.setAttribute('aria-label', ariaLabel);
},
shouldAcceptDrag: function(e) {
// Only allow page switching when a drop could happen on the page being
// switched to.
var nextPage = ntp.getCardSlider().getCardAtIndex(this.nextCardIndex_());
return nextPage.shouldAcceptDrag(e);
},
doDragEnter: function(e) {
this.scheduleDelayedSwitch_(e);
this.doDragOver(e);
},
doDragLeave: function(e) {
this.cancelDelayedSwitch_();
},
doDragOver: function(e) {
e.preventDefault();
var targetPage = ntp.getCardSlider().currentCardValue;
if (targetPage.shouldAcceptDrag(e))
targetPage.setDropEffect(e.dataTransfer);
},
doDrop: function(e) {
e.stopPropagation();
this.cancelDelayedSwitch_();
var tile = ntp.getCurrentlyDraggingTile();
if (!tile)
return;
var sourcePage = tile.tilePage;
var targetPage = ntp.getCardSlider().currentCardValue;
if (targetPage == sourcePage || !targetPage.shouldAcceptDrag(e))
return;
targetPage.appendDraggingTile();
},
/**
* Starts a timer to activate the switcher. The timer repeats until
* cancelled by cancelDelayedSwitch_.
* @private
*/
scheduleDelayedSwitch_: function(e) {
// Stop switching when the next page can't be dropped onto.
var nextPage = ntp.getCardSlider().getCardAtIndex(this.nextCardIndex_());
if (!nextPage.shouldAcceptDrag(e))
return;
var self = this;
function navPageClearTimeout() {
self.activate_();
self.dragNavTimeout_ = null;
self.scheduleDelayedSwitch_(e);
}
this.dragNavTimeout_ = window.setTimeout(navPageClearTimeout, 500);
},
/**
* Cancels the timer that activates the switcher while dragging.
* @private
*/
cancelDelayedSwitch_: function() {
if (this.dragNavTimeout_) {
window.clearTimeout(this.dragNavTimeout_);
this.dragNavTimeout_ = null;
}
},
};
return {
initializePageSwitcher: PageSwitcher.template.decorate
};
});
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