57 lines
1.7 KiB
JavaScript
57 lines
1.7 KiB
JavaScript
import { WINDOW } from '../../types.js';
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import { onHidden } from './onHidden.js';
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/*
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* Copyright 2020 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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let firstHiddenTime = -1;
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const initHiddenTime = () => {
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// If the document is hidden and not prerendering, assume it was always
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// hidden and the page was loaded in the background.
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if (WINDOW.document && WINDOW.document.visibilityState) {
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firstHiddenTime = WINDOW.document.visibilityState === 'hidden' && !WINDOW.document.prerendering ? 0 : Infinity;
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}
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};
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const trackChanges = () => {
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// Update the time if/when the document becomes hidden.
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onHidden(({ timeStamp }) => {
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firstHiddenTime = timeStamp;
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}, true);
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};
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const getVisibilityWatcher = (
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) => {
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if (firstHiddenTime < 0) {
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// If the document is hidden when this code runs, assume it was hidden
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// since navigation start. This isn't a perfect heuristic, but it's the
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// best we can do until an API is available to support querying past
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// visibilityState.
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initHiddenTime();
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trackChanges();
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}
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return {
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get firstHiddenTime() {
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return firstHiddenTime;
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},
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};
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};
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export { getVisibilityWatcher };
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//# sourceMappingURL=getVisibilityWatcher.js.map
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