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| 1 | +<!doctype html> |
| 2 | +<!-- |
| 3 | +@license |
| 4 | +Copyright (c) 2016 The Polymer Project Authors. All rights reserved. |
| 5 | +This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt |
| 6 | +The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt |
| 7 | +The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt |
| 8 | +Code distributed by Google as part of the polymer project is also |
| 9 | +subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt |
| 10 | +--> |
| 11 | +<link rel="import" href="../polymer/polymer.html"> |
| 12 | + |
| 13 | +<script> |
| 14 | + (function() { |
| 15 | + 'use strict'; |
| 16 | + |
| 17 | + var p = Element.prototype; |
| 18 | + var matches = p.matches || p.matchesSelector || p.mozMatchesSelector || |
| 19 | + p.msMatchesSelector || p.oMatchesSelector || p.webkitMatchesSelector; |
| 20 | + |
| 21 | + Polymer.IronFocusablesHelper = { |
| 22 | + |
| 23 | + /** |
| 24 | + * Returns a sorted array of tabbable nodes, including the root node. |
| 25 | + * It searches the tabbable nodes in the light and shadow dom of the chidren, |
| 26 | + * sorting the result by tabindex. |
| 27 | + * @param {!Node} node |
| 28 | + * @return {Array<HTMLElement>} |
| 29 | + */ |
| 30 | + getTabbableNodes: function(node) { |
| 31 | + var result = []; |
| 32 | + // If there is at least one element with tabindex > 0, we need to sort |
| 33 | + // the final array by tabindex. |
| 34 | + var needsSortByTabIndex = this._collectTabbableNodes(node, result); |
| 35 | + if (needsSortByTabIndex) { |
| 36 | + return this._sortByTabIndex(result); |
| 37 | + } |
| 38 | + return result; |
| 39 | + }, |
| 40 | + |
| 41 | + /** |
| 42 | + * Returns if a element is focusable. |
| 43 | + * @param {!HTMLElement} element |
| 44 | + * @return {boolean} |
| 45 | + */ |
| 46 | + isFocusable: function(element) { |
| 47 | + // From http://stackoverflow.com/a/1600194/4228703: |
| 48 | + // There isn't a definite list, it's up to the browser. The only |
| 49 | + // standard we have is DOM Level 2 HTML https://www.w3.org/TR/DOM-Level-2-HTML/html.html, |
| 50 | + // according to which the only elements that have a focus() method are |
| 51 | + // HTMLInputElement, HTMLSelectElement, HTMLTextAreaElement and |
| 52 | + // HTMLAnchorElement. This notably omits HTMLButtonElement and |
| 53 | + // HTMLAreaElement. |
| 54 | + // Referring to these tests with tabbables in different browsers |
| 55 | + // http://allyjs.io/data-tables/focusable.html |
| 56 | + |
| 57 | + // Elements that cannot be focused if they have [disabled] attribute. |
| 58 | + if (matches.call(element, 'input, select, textarea, button, object')) { |
| 59 | + return matches.call(element, ':not([disabled])'); |
| 60 | + } |
| 61 | + // Elements that can be focused even if they have [disabled] attribute. |
| 62 | + return matches.call(element, |
| 63 | + 'a[href], area[href], iframe, [tabindex], [contentEditable]'); |
| 64 | + }, |
| 65 | + |
| 66 | + /** |
| 67 | + * Returns if a element is tabbable. To be tabbable, a element must be |
| 68 | + * focusable, visible, and with a tabindex !== -1. |
| 69 | + * @param {!HTMLElement} element |
| 70 | + * @return {boolean} |
| 71 | + */ |
| 72 | + isTabbable: function(element) { |
| 73 | + return this.isFocusable(element) && |
| 74 | + matches.call(element, ':not([tabindex="-1"])') && |
| 75 | + this._isVisible(element); |
| 76 | + }, |
| 77 | + |
| 78 | + /** |
| 79 | + * Returns the normalized element tabindex. If not focusable, returns -1. |
| 80 | + * It checks for the attribute "tabindex" instead of the element property |
| 81 | + * `tabIndex` since browsers assign different values to it. |
| 82 | + * e.g. in Firefox `<div contenteditable>` has `tabIndex = -1` |
| 83 | + * @param {!HTMLElement} element |
| 84 | + * @return {!number} |
| 85 | + * @private |
| 86 | + */ |
| 87 | + _normalizedTabIndex: function(element) { |
| 88 | + if (this.isFocusable(element)) { |
| 89 | + var tabIndex = element.getAttribute('tabindex') || 0; |
| 90 | + return Number(tabIndex); |
| 91 | + } |
| 92 | + return -1; |
| 93 | + }, |
| 94 | + |
| 95 | + /** |
| 96 | + * Searches for nodes that are tabbable and adds them to the `result` array. |
| 97 | + * Returns if the `result` array needs to be sorted by tabindex. |
| 98 | + * @param {!Node} node The starting point for the search; added to `result` |
| 99 | + * if tabbable. |
| 100 | + * @param {!Array<HTMLElement>} result |
| 101 | + * @return {boolean} |
| 102 | + * @private |
| 103 | + */ |
| 104 | + _collectTabbableNodes: function(node, result) { |
| 105 | + // If not an element or not visible, no need to explore children. |
| 106 | + if (node.nodeType !== Node.ELEMENT_NODE || !this._isVisible(node)) { |
| 107 | + return false; |
| 108 | + } |
| 109 | + var element = /** @type {HTMLElement} */ (node); |
| 110 | + var tabIndex = this._normalizedTabIndex(element); |
| 111 | + var needsSortByTabIndex = tabIndex > 0; |
| 112 | + if (tabIndex >= 0) { |
| 113 | + result.push(element); |
| 114 | + } |
| 115 | + |
| 116 | + // In ShadowDOM v1, tab order is affected by the order of distrubution. |
| 117 | + // E.g. getTabbableNodes(#root) in ShadowDOM v1 should return [#A, #B]; |
| 118 | + // in ShadowDOM v0 tab order is not affected by the distrubution order, |
| 119 | + // in fact getTabbableNodes(#root) returns [#B, #A]. |
| 120 | + // <div id="root"> |
| 121 | + // <!-- shadow --> |
| 122 | + // <slot name="a"> |
| 123 | + // <slot name="b"> |
| 124 | + // <!-- /shadow --> |
| 125 | + // <input id="A" slot="a"> |
| 126 | + // <input id="B" slot="b" tabindex="1"> |
| 127 | + // </div> |
| 128 | + // TODO(valdrin) support ShadowDOM v1 when upgrading to Polymer v2.0. |
| 129 | + var children; |
| 130 | + if (element.localName === 'content') { |
| 131 | + children = Polymer.dom(element).getDistributedNodes(); |
| 132 | + } else { |
| 133 | + // Use shadow root if possible, will check for distributed nodes. |
| 134 | + children = Polymer.dom(element.root || element).children; |
| 135 | + } |
| 136 | + for (var i = 0; i < children.length; i++) { |
| 137 | + // Ensure method is always invoked to collect tabbable children. |
| 138 | + var needsSort = this._collectTabbableNodes(children[i], result); |
| 139 | + needsSortByTabIndex = needsSortByTabIndex || needsSort; |
| 140 | + } |
| 141 | + return needsSortByTabIndex; |
| 142 | + }, |
| 143 | + |
| 144 | + /** |
| 145 | + * Returns false if the element has `visibility: hidden` or `display: none` |
| 146 | + * @param {!HTMLElement} element |
| 147 | + * @return {boolean} |
| 148 | + * @private |
| 149 | + */ |
| 150 | + _isVisible: function(element) { |
| 151 | + // Check inline style first to save a re-flow. If looks good, check also |
| 152 | + // computed style. |
| 153 | + var style = element.style; |
| 154 | + if (style.visibility !== 'hidden' && style.display !== 'none') { |
| 155 | + style = window.getComputedStyle(element); |
| 156 | + return (style.visibility !== 'hidden' && style.display !== 'none'); |
| 157 | + } |
| 158 | + return false; |
| 159 | + }, |
| 160 | + |
| 161 | + /** |
| 162 | + * Sorts an array of tabbable elements by tabindex. Returns a new array. |
| 163 | + * @param {!Array<HTMLElement>} tabbables |
| 164 | + * @return {Array<HTMLElement>} |
| 165 | + * @private |
| 166 | + */ |
| 167 | + _sortByTabIndex: function(tabbables) { |
| 168 | + // Implement a merge sort as Array.prototype.sort does a non-stable sort |
| 169 | + // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort |
| 170 | + var len = tabbables.length; |
| 171 | + if (len < 2) { |
| 172 | + return tabbables; |
| 173 | + } |
| 174 | + var pivot = Math.ceil(len / 2); |
| 175 | + var left = this._sortByTabIndex(tabbables.slice(0, pivot)); |
| 176 | + var right = this._sortByTabIndex(tabbables.slice(pivot)); |
| 177 | + return this._mergeSortByTabIndex(left, right); |
| 178 | + }, |
| 179 | + |
| 180 | + /** |
| 181 | + * Merge sort iterator, merges the two arrays into one, sorted by tab index. |
| 182 | + * @param {!Array<HTMLElement>} left |
| 183 | + * @param {!Array<HTMLElement>} right |
| 184 | + * @return {Array<HTMLElement>} |
| 185 | + * @private |
| 186 | + */ |
| 187 | + _mergeSortByTabIndex: function(left, right) { |
| 188 | + var result = []; |
| 189 | + while ((left.length > 0) && (right.length > 0)) { |
| 190 | + if (this._hasLowerTabOrder(left[0], right[0])) { |
| 191 | + result.push(right.shift()); |
| 192 | + } else { |
| 193 | + result.push(left.shift()); |
| 194 | + } |
| 195 | + } |
| 196 | + |
| 197 | + return result.concat(left, right); |
| 198 | + }, |
| 199 | + |
| 200 | + /** |
| 201 | + * Returns if element `a` has lower tab order compared to element `b` |
| 202 | + * (both elements are assumed to be focusable and tabbable). |
| 203 | + * Elements with tabindex = 0 have lower tab order compared to elements |
| 204 | + * with tabindex > 0. |
| 205 | + * If both have same tabindex, it returns false. |
| 206 | + * @param {!HTMLElement} a |
| 207 | + * @param {!HTMLElement} b |
| 208 | + * @return {boolean} |
| 209 | + * @private |
| 210 | + */ |
| 211 | + _hasLowerTabOrder: function(a, b) { |
| 212 | + // Normalize tabIndexes |
| 213 | + // e.g. in Firefox `<div contenteditable>` has `tabIndex = -1` |
| 214 | + var ati = Math.max(a.tabIndex, 0); |
| 215 | + var bti = Math.max(b.tabIndex, 0); |
| 216 | + return (ati === 0 || bti === 0) ? bti > ati : ati > bti; |
| 217 | + } |
| 218 | + }; |
| 219 | + })(); |
| 220 | +</script> |
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