polygerrit-ui/app/styles/gr-a11y-styles.ts

/**
 * @license
 * Copyright (C) 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import {css} from 'lit';

export const a11yStyles = css`
  .assistive-tech-only {
    user-select: none;
    clip: rect(1px, 1px, 1px, 1px);
    height: 1px;
    margin: 0;
    overflow: hidden;
    padding: 0;
    position: absolute;
    white-space: nowrap;
    width: 1px;
    z-index: -1000;
  }
`;

const $_documentContainer = document.createElement('template');
$_documentContainer.innerHTML = `<dom-module id="gr-a11y-styles">
  <template>
    <style>
    ${a11yStyles.cssText}
    </style>
  </template>
</dom-module>`;
document.head.appendChild($_documentContainer.content);