@logo-elements/overlay
Version:
<logo-elements-overlay> is a Web Component meant for internal use in Logo Elements web components to overlay items.
212 lines (198 loc) • 7.57 kB
JavaScript
/**
* @license
* Copyright LOGO YAZILIM SANAYİ VE TİCARET A.Ş. All Rights Reserved.
*
* Save to the extent permitted by law, you may not use, copy, modify,
* distribute or create derivative works of this material or any part
* of it without the prior written consent of LOGO YAZILIM SANAYİ VE TİCARET A.Ş. Limited.
* Any reproduction of this material must contain this notice.
*/
/**
* `Polymer.IronFocusablesHelper` relies on some Polymer-specific legacy API,
* especially the `root` property which does not exist for native shadow DOM.
* That's why we have this helper here.
* See https://github.com/PolymerElements/iron-overlay-behavior/issues/282
*/
class FocusablesHelper {
/**
* Returns a sorted array of tabbable nodes, including the root node.
* It searches the tabbable nodes in the light and shadow dom of the children,
* sorting the result by tabindex.
* @param {!Node} node
* @return {!Array<!HTMLElement>}
*/
static getTabbableNodes(node) {
const result = [];
// If there is at least one element with tabindex > 0, we need to sort
// the final array by tabindex.
const needsSortByTabIndex = this._collectTabbableNodes(node, result);
if (needsSortByTabIndex) {
return this._sortByTabIndex(result);
}
return result;
}
/**
* Returns if a element is focusable.
* @param {!HTMLElement} element
* @return {boolean}
*/
static isFocusable(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 (element.matches('input, select, textarea, button, object')) {
return element.matches(':not([disabled])');
}
// Elements that can be focused even if they have [disabled] attribute.
return element.matches('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}
*/
static isTabbable(element) {
return this.isFocusable(element) && element.matches(':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
*/
static _normalizedTabIndex(element) {
if (this.isFocusable(element)) {
const 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
*/
static _collectTabbableNodes(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;
}
const element = /** @type {!HTMLElement} */ (node);
const tabIndex = this._normalizedTabIndex(element);
let needsSort = tabIndex > 0;
if (tabIndex >= 0) {
result.push(element);
}
// In ShadowDOM v1, tab order is affected by the order of distribution.
// E.g. getTabbableNodes(#root) in ShadowDOM v1 should return [#A, #B];
// in ShadowDOM v0 tab order is not affected by the distribution 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>
let children;
if (element.localName === 'slot') {
children = element.assignedNodes({ flatten: true });
} else {
// Use shadow root if possible, will check for distributed nodes.
children = (element.shadowRoot || element).children;
}
if (children) {
for (let 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
*/
static _isVisible(element) {
// Check inline style first to save a re-flow. If looks good, check also
// computed style.
let 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
*/
static _sortByTabIndex(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
const len = tabbables.length;
if (len < 2) {
return tabbables;
}
const pivot = Math.ceil(len / 2);
const left = this._sortByTabIndex(tabbables.slice(0, pivot));
const 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
*/
static _mergeSortByTabIndex(left, right) {
const 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
*/
static _hasLowerTabOrder(a, b) {
// Normalize tabIndexes
// e.g. in Firefox `<div contenteditable>` has `tabIndex = -1`
const ati = Math.max(a.tabIndex, 0);
const bti = Math.max(b.tabIndex, 0);
return ati === 0 || bti === 0 ? bti > ati : ati > bti;
}
}
export { FocusablesHelper };