/* * 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); }); }); }); } };