| 1 | /**
|
| 2 | * @license
|
| 3 | * Copyright 2018 Google Inc.
|
| 4 | *
|
| 5 | * Permission is hereby granted, free of charge, to any person obtaining a copy
|
| 6 | * of this software and associated documentation files (the "Software"), to deal
|
| 7 | * in the Software without restriction, including without limitation the rights
|
| 8 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
| 9 | * copies of the Software, and to permit persons to whom the Software is
|
| 10 | * furnished to do so, subject to the following conditions:
|
| 11 | *
|
| 12 | * The above copyright notice and this permission notice shall be included in
|
| 13 | * all copies or substantial portions of the Software.
|
| 14 | *
|
| 15 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
| 16 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
| 17 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
| 18 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
| 19 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
| 20 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
| 21 | * THE SOFTWARE.
|
| 22 | */
|
| 23 | import { numbers, strings } from './constants';
|
| 24 | var ARIA_LIVE_DELAY_MS = numbers.ARIA_LIVE_DELAY_MS;
|
| 25 | var ARIA_LIVE_LABEL_TEXT_ATTR = strings.ARIA_LIVE_LABEL_TEXT_ATTR;
|
| 26 | function announce(ariaEl, labelEl) {
|
| 27 | if (labelEl === void 0) { labelEl = ariaEl; }
|
| 28 | var priority = ariaEl.getAttribute('aria-live');
|
| 29 | // Trim text to ignore ` ` (see below).
|
| 30 | // textContent is only null if the node is a document, DOCTYPE, or notation.
|
| 31 | var labelText = labelEl.textContent.trim();
|
| 32 | if (!labelText || !priority) {
|
| 33 | return;
|
| 34 | }
|
| 35 | // Temporarily disable `aria-live` to prevent JAWS+Firefox from announcing the message twice.
|
| 36 | ariaEl.setAttribute('aria-live', 'off');
|
| 37 | // Temporarily clear `textContent` to force a DOM mutation event that will be detected by screen readers.
|
| 38 | // `aria-live` elements are only announced when the element's `textContent` *changes*, so snackbars
|
| 39 | // sent to the browser in the initial HTML response won't be read unless we clear the element's `textContent` first.
|
| 40 | // Similarly, displaying the same snackbar message twice in a row doesn't trigger a DOM mutation event,
|
| 41 | // so screen readers won't announce the second message unless we first clear `textContent`.
|
| 42 | //
|
| 43 | // We have to clear the label text two different ways to make it work in all browsers and screen readers:
|
| 44 | //
|
| 45 | // 1. `textContent = ''` is required for IE11 + JAWS
|
| 46 | // 2. `innerHTML = ' '` is required for Chrome + JAWS and NVDA
|
| 47 | //
|
| 48 | // All other browser/screen reader combinations support both methods.
|
| 49 | //
|
| 50 | // The wrapper `<span>` visually hides the space character so that it doesn't cause jank when added/removed.
|
| 51 | // N.B.: Setting `position: absolute`, `opacity: 0`, or `height: 0` prevents Chrome from detecting the DOM change.
|
| 52 | //
|
| 53 | // This technique has been tested in:
|
| 54 | //
|
| 55 | // * JAWS 2019:
|
| 56 | // - Chrome 70
|
| 57 | // - Firefox 60 (ESR)
|
| 58 | // - IE 11
|
| 59 | // * NVDA 2018:
|
| 60 | // - Chrome 70
|
| 61 | // - Firefox 60 (ESR)
|
| 62 | // - IE 11
|
| 63 | // * ChromeVox 53
|
| 64 | labelEl.textContent = '';
|
| 65 | labelEl.innerHTML = '<span style="display: inline-block; width: 0; height: 1px;"> </span>';
|
| 66 | // Prevent visual jank by temporarily displaying the label text in the ::before pseudo-element.
|
| 67 | // CSS generated content is normally announced by screen readers
|
| 68 | // (except in IE 11; see https://tink.uk/accessibility-support-for-css-generated-content/);
|
| 69 | // however, `aria-live` is turned off, so this DOM update will be ignored by screen readers.
|
| 70 | labelEl.setAttribute(ARIA_LIVE_LABEL_TEXT_ATTR, labelText);
|
| 71 | setTimeout(function () {
|
| 72 | // Allow screen readers to announce changes to the DOM again.
|
| 73 | ariaEl.setAttribute('aria-live', priority);
|
| 74 | // Remove the message from the ::before pseudo-element.
|
| 75 | labelEl.removeAttribute(ARIA_LIVE_LABEL_TEXT_ATTR);
|
| 76 | // Restore the original label text, which will be announced by screen readers.
|
| 77 | labelEl.textContent = labelText;
|
| 78 | }, ARIA_LIVE_DELAY_MS);
|
| 79 | }
|
| 80 | export { announce };
|
| 81 | //# sourceMappingURL=util.js.map |
| \ | No newline at end of file |