/**
@license
Copyright (c) 2016 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at
http://polymer.github.io/LICENSE.txt The complete set of authors may be found at
http://polymer.github.io/AUTHORS.txt The complete set of contributors may be
found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by Google as
part of the polymer project is also subject to an additional IP rights grant
found at http://polymer.github.io/PATENTS.txt
*/
import '../polymer/polymer_bundled.min.js';
import {dom} from '../polymer/polymer_bundled.min.js';
var p = Element.prototype;
var matches = p.matches || p.matchesSelector || p.mozMatchesSelector ||
p.msMatchesSelector || p.oMatchesSelector || p.webkitMatchesSelector;
export const IronFocusablesHelper = {
/**
* Returns a sorted array of tabbable nodes, including the root node.
* It searches the tabbable nodes in the light and shadow dom of the chidren,
* sorting the result by tabindex.
* @param {!Node} node
* @return {!Array<!HTMLElement>}
*/
getTabbableNodes: function(node) {
var result = [];
// If there is at least one element with tabindex > 0, we need to sort
// the final array by tabindex.
var needsSortByTabIndex = this._collectTabbableNodes(node, result);
if (needsSortByTabIndex) {
return this._sortByTabIndex(result);
}
return result;
},
/**
* Returns if a element is focusable.
* @param {!HTMLElement} element
* @return {boolean}
*/
isFocusable: function(element) {
// From http://stackoverflow.com/a/1600194/4228703:
// There isn't a definite list, it's up to the browser. The only
// standard we have is DOM Level 2 HTML
// https://www.w3.org/TR/DOM-Level-2-HTML/html.html, according to which the
// only elements that have a focus() method are HTMLInputElement,
// HTMLSelectElement, HTMLTextAreaElement and HTMLAnchorElement. This
// notably omits HTMLButtonElement and HTMLAreaElement. Referring to these
// tests with tabbables in different browsers
// http://allyjs.io/data-tables/focusable.html
// Elements that cannot be focused if they have [disabled] attribute.
if (matches.call(element, 'input, select, textarea, button, object')) {
return matches.call(element, ':not([disabled])');
}
// Elements that can be focused even if they have [disabled] attribute.
return matches.call(
element, 'a[href], area[href], iframe, [tabindex], [contentEditable]');
},
/**
* Returns if a element is tabbable. To be tabbable, a element must be
* focusable, visible, and with a tabindex !== -1.
* @param {!HTMLElement} element
* @return {boolean}
*/
isTabbable: function(element) {
return this.isFocusable(element) &&
matches.call(element, ':not([tabindex="-1"])') &&
this._isVisible(element);
},
/**
* Returns the normalized element tabindex. If not focusable, returns -1.
* It checks for the attribute "tabindex" instead of the element property
* `tabIndex` since browsers assign different values to it.
* e.g. in Firefox `<div contenteditable>` has `tabIndex = -1`
* @param {!HTMLElement} element
* @return {!number}
* @private
*/
_normalizedTabIndex: function(element) {
if (this.isFocusable(element)) {
var tabIndex = element.getAttribute('tabindex') || 0;
return Number(tabIndex);
}
return -1;
},
/**
* Searches for nodes that are tabbable and adds them to the `result` array.
* Returns if the `result` array needs to be sorted by tabindex.
* @param {!Node} node The starting point for the search; added to `result`
* if tabbable.
* @param {!Array<!HTMLElement>} result
* @return {boolean}
* @private
*/
_collectTabbableNodes: function(node, result) {
// If not an element or not visible, no need to explore children.
if (node.nodeType !== Node.ELEMENT_NODE || !this._isVisible(node)) {
return false;
}
var element = /** @type {!HTMLElement} */ (node);
var tabIndex = this._normalizedTabIndex(element);
var needsSort = tabIndex > 0;
if (tabIndex >= 0) {
result.push(element);
}
// In ShadowDOM v1, tab order is affected by the order of distrubution.
// E.g. getTabbableNodes(#root) in ShadowDOM v1 should return [#A, #B];
// in ShadowDOM v0 tab order is not affected by the distrubution order,
// in fact getTabbableNodes(#root) returns [#B, #A].
// <div id="root">
// <!-- shadow -->
// <slot name="a">
// <slot name="b">
// <!-- /shadow -->
// <input id="A" slot="a">
// <input id="B" slot="b" tabindex="1">
// </div>
// TODO(valdrin) support ShadowDOM v1 when upgrading to Polymer v2.0.
var children;
if (element.localName === 'content' || element.localName === 'slot') {
children = dom(element).getDistributedNodes();
} else {
// Use shadow root if possible, will check for distributed nodes.
children = dom(element.root || element).children;
}
for (var i = 0; i < children.length; i++) {
// Ensure method is always invoked to collect tabbable children.
needsSort = this._collectTabbableNodes(children[i], result) || needsSort;
}
return needsSort;
},
/**
* Returns false if the element has `visibility: hidden` or `display: none`
* @param {!HTMLElement} element
* @return {boolean}
* @private
*/
_isVisible: function(element) {
// Check inline style first to save a re-flow. If looks good, check also
// computed style.
var style = element.style;
if (style.visibility !== 'hidden' && style.display !== 'none') {
style = window.getComputedStyle(element);
return (style.visibility !== 'hidden' && style.display !== 'none');
}
return false;
},
/**
* Sorts an array of tabbable elements by tabindex. Returns a new array.
* @param {!Array<!HTMLElement>} tabbables
* @return {!Array<!HTMLElement>}
* @private
*/
_sortByTabIndex: function(tabbables) {
// Implement a merge sort as Array.prototype.sort does a non-stable sort
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort
var len = tabbables.length;
if (len < 2) {
return tabbables;
}
var pivot = Math.ceil(len / 2);
var left = this._sortByTabIndex(tabbables.slice(0, pivot));
var right = this._sortByTabIndex(tabbables.slice(pivot));
return this._mergeSortByTabIndex(left, right);
},
/**
* Merge sort iterator, merges the two arrays into one, sorted by tab index.
* @param {!Array<!HTMLElement>} left
* @param {!Array<!HTMLElement>} right
* @return {!Array<!HTMLElement>}
* @private
*/
_mergeSortByTabIndex: function(left, right) {
var result = [];
while ((left.length > 0) && (right.length > 0)) {
if (this._hasLowerTabOrder(left[0], right[0])) {
result.push(right.shift());
} else {
result.push(left.shift());
}
}
return result.concat(left, right);
},
/**
* Returns if element `a` has lower tab order compared to element `b`
* (both elements are assumed to be focusable and tabbable).
* Elements with tabindex = 0 have lower tab order compared to elements
* with tabindex > 0.
* If both have same tabindex, it returns false.
* @param {!HTMLElement} a
* @param {!HTMLElement} b
* @return {boolean}
* @private
*/
_hasLowerTabOrder: function(a, b) {
// Normalize tabIndexes
// e.g. in Firefox `<div contenteditable>` has `tabIndex = -1`
var ati = Math.max(a.tabIndex, 0);
var bti = Math.max(b.tabIndex, 0);
return (ati === 0 || bti === 0) ? bti > ati : ati > bti;
}
};
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