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/*
* Copyright 2022 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 { onBFCacheRestore } from './lib/bfcache.js';
import { bindReporter } from './lib/bindReporter.js';
import { initMetric } from './lib/initMetric.js';
import { DEFAULT_DURATION_THRESHOLD, processInteractionEntry, estimateP98LongestInteraction, resetInteractions, } from './lib/interactions.js';
import { observe } from './lib/observe.js';
import { onHidden } from './lib/onHidden.js';
import { initInteractionCountPolyfill } from './lib/polyfills/interactionCountPolyfill.js';
import { whenActivated } from './lib/whenActivated.js';
import { whenIdle } from './lib/whenIdle.js';
/** Thresholds for INP. See https://web.dev/articles/inp#what_is_a_good_inp_score */
export const INPThresholds = [200, 500];
/**
* Calculates the [INP](https://web.dev/articles/inp) value for the current
* page and calls the `callback` function once the value is ready, along with
* the `event` performance entries reported for that interaction. The reported
* value is a `DOMHighResTimeStamp`.
*
* A custom `durationThreshold` configuration option can optionally be passed to
* control what `event-timing` entries are considered for INP reporting. The
* default threshold is `40`, which means INP scores of less than 40 are
* reported as 0. Note that this will not affect your 75th percentile INP value
* unless that value is also less than 40 (well below the recommended
* [good](https://web.dev/articles/inp#what_is_a_good_inp_score) threshold).
*
* If the `reportAllChanges` configuration option is set to `true`, the
* `callback` function will be called as soon as the value is initially
* determined as well as any time the value changes throughout the page
* lifespan.
*
* _**Important:** INP should be continually monitored for changes throughout
* the entire lifespan of a page—including if the user returns to the page after
* it's been hidden/backgrounded. However, since browsers often [will not fire
* additional callbacks once the user has backgrounded a
* page](https://developer.chrome.com/blog/page-lifecycle-api/#advice-hidden),
* `callback` is always called when the page's visibility state changes to
* hidden. As a result, the `callback` function might be called multiple times
* during the same page load._
*/
export const onINP = (onReport, opts) => {
// Return if the browser doesn't support all APIs needed to measure INP.
if (!('PerformanceEventTiming' in self &&
'interactionId' in PerformanceEventTiming.prototype)) {
return;
}
// Set defaults
opts = opts || {};
whenActivated(() => {
// TODO(philipwalton): remove once the polyfill is no longer needed.
initInteractionCountPolyfill();
let metric = initMetric('INP');
let report;
const handleEntries = (entries) => {
// Queue the `handleEntries()` callback in the next idle task.
// This is needed to increase the chances that all event entries that
// occurred between the user interaction and the next paint
// have been dispatched. Note: there is currently an experiment
// running in Chrome (EventTimingKeypressAndCompositionInteractionId)
// 123+ that if rolled out fully may make this no longer necessary.
whenIdle(() => {
entries.forEach(processInteractionEntry);
const inp = estimateP98LongestInteraction();
if (inp && inp.latency !== metric.value) {
metric.value = inp.latency;
metric.entries = inp.entries;
report();
}
});
};
const po = observe('event', handleEntries, {
// Event Timing entries have their durations rounded to the nearest 8ms,
// so a duration of 40ms would be any event that spans 2.5 or more frames
// at 60Hz. This threshold is chosen to strike a balance between usefulness
// and performance. Running this callback for any interaction that spans
// just one or two frames is likely not worth the insight that could be
// gained.
durationThreshold: opts.durationThreshold ?? DEFAULT_DURATION_THRESHOLD,
});
report = bindReporter(onReport, metric, INPThresholds, opts.reportAllChanges);
if (po) {
// Also observe entries of type `first-input`. This is useful in cases
// where the first interaction is less than the `durationThreshold`.
po.observe({ type: 'first-input', buffered: true });
onHidden(() => {
handleEntries(po.takeRecords());
report(true);
});
// Only report after a bfcache restore if the `PerformanceObserver`
// successfully registered.
onBFCacheRestore(() => {
resetInteractions();
metric = initMetric('INP');
report = bindReporter(onReport, metric, INPThresholds, opts.reportAllChanges);
});
}
});
};
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