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/*
* Copyright 2020 Google LLC
*
* 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
*
* https://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 { bindReporter } from './lib/bindReporter.js';
import { getVisibilityWatcher } from './lib/getVisibilityWatcher.js';
import { initMetric } from './lib/initMetric.js';
import { observe } from './lib/observe.js';
import { onBFCacheRestore } from './lib/onBFCacheRestore.js';
export const getFCP = (onReport, reportAllChanges) => {
const visibilityWatcher = getVisibilityWatcher();
let metric = initMetric('FCP');
let report;
const entryHandler = (entry) => {
if (entry.name === 'first-contentful-paint') {
if (po) {
po.disconnect();
}
// Only report if the page wasn't hidden prior to the first paint.
if (entry.startTime < visibilityWatcher.firstHiddenTime) {
metric.value = entry.startTime;
metric.entries.push(entry);
report(true);
}
}
};
// TODO(philipwalton): remove the use of `fcpEntry` once this bug is fixed.
// https://bugs.webkit.org/show_bug.cgi?id=225305
// The check for `getEntriesByName` is needed to support Opera:
// https://github.com/GoogleChrome/web-vitals/issues/159
// The check for `window.performance` is needed to support Opera mini:
// https://github.com/GoogleChrome/web-vitals/issues/185
const fcpEntry = window.performance && performance.getEntriesByName &&
performance.getEntriesByName('first-contentful-paint')[0];
const po = fcpEntry ? null : observe('paint', entryHandler);
if (fcpEntry || po) {
report = bindReporter(onReport, metric, reportAllChanges);
if (fcpEntry) {
entryHandler(fcpEntry);
}
onBFCacheRestore((event) => {
metric = initMetric('FCP');
report = bindReporter(onReport, metric, reportAllChanges);
requestAnimationFrame(() => {
requestAnimationFrame(() => {
metric.value = performance.now() - event.timeStamp;
report(true);
});
});
});
}
};