test/views/layout.njk

<!DOCTYPE html>
<!--
 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.
-->
<html lang="en" {% if invisible or hidden %}hidden{% endif %}>
<head>
  <meta charset="utf-8">
  <title>Web Vitals Test</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <script>
    (function() {
      /**
       * @param {string} visibilityState
       * @return {void}
       */
      self.__stubVisibilityState = (visibilityState) => {
        if (visibilityState === 'hidden') {
          Object.defineProperty(document, 'visibilityState', {
            value: visibilityState,
            configurable: true,
          });
          document.documentElement.hidden = true;
        } else {
          delete document.visibilityState;
          document.documentElement.hidden = false;
        }
      }

      /**
       * @param {string} visibilityState
       * @return {void}
       */
      self.__stubVisibilityChange = (visibilityState) => {
        self.__stubVisibilityState(visibilityState)
        document.dispatchEvent(new Event('visibilitychange'));
      }

      /**
       * @param {string} visibilityStateAfterRestore
       * @return {Promise<void>}
       */
      self.__stubForwardBack = (visibilityStateAfterRestore) => {
        return new Promise((resolve) => {
          window.dispatchEvent(new PageTransitionEvent('pagehide', {
            persisted: true,
          }));
          self.__stubVisibilityChange('hidden');
          requestAnimationFrame(() => {
            requestAnimationFrame(() => {
              if (visibilityStateAfterRestore !== 'hidden') {
                self.__stubVisibilityChange('visible');
              }
              window.dispatchEvent(new PageTransitionEvent('pageshow', {
                persisted: true,
              }));
              resolve();
            });
          });
        });
      }

      /**
       * @return {Promise<void>}
       */
      self.__stubPrerender = () => {
        return new Promise((resolve) => {
          const navEntry = performance.getEntriesByType('navigation')[0];
          // Only stub if the page isn't actually prerendered.
          if (!(document.prerendering || navEntry.activationStart > 0)) {
            self.__stubVisibilityState('hidden');
            Object.defineProperty(document, 'prerendering', {
              value: true,
              configurable: true,
            });
            setTimeout(() => {
              const time = self.performance ? performance.now() : 0;
              const fcpEntry = performance.getEntriesByName('first-contentful-paint')[0];
              Object.defineProperty(navEntry, 'activationStart', {
                configurable: true,
                enumerable: true,
                value: Math.min(time, fcpEntry && fcpEntry.startTime || time),
              });
              self.__stubVisibilityChange('visible');
              delete document.prerendering;
              document.dispatchEvent(new Event('prerenderingchange'));
              resolve();
            }, Number(params.get('prerender')) || 0);
          }
        });
      }

      /**
       * @return {Promise<void>}
       */
      self.__stubWasDiscarded = () => {
        return new Promise((resolve) => {
          // Only stub if the page isn't actually discarded.
          if (!document.wasDiscarded) {
            Object.defineProperty(document, 'wasDiscarded', {
              value: true,
              configurable: true,
            });
          }
        });
      }

      // Uncomment to stub running in a browser that doesn't support performance APIs
      // (e.g. some version of Opera support this).
      // delete self.performance;

      const params = new URL(location.href).searchParams;

      if (params.has('reportAllChanges')) {
        self.__reportAllChanges = Boolean(params.get('reportAllChanges'));
      }

      if (params.has('durationThreshold')) {
        self.__durationThreshold = Number(params.get('durationThreshold'));
      }

      if (params.has('hidden')) {
        // Stub the page being loaded in the hidden state, but defer to the
        // native state if the `visibilitychange` event fires.
        Object.defineProperty(document, 'visibilityState', {
          value: 'hidden',
          configurable: true,
        });
        addEventListener('visibilitychange', (event) => {
          if (event.isTrusted) {
            delete document.visibilityState;
          }
        }, true);
      }

      if (params.has('prerender')) {
        self.__stubPrerender();
      }

      if (params.has('wasDiscarded')) {
        self.__stubWasDiscarded();
      }
    }());
  </script>
  {% if polyfill %}
    <script>{{ webVitalsPolyfill | safe }}</script>
  {% endif %}
  {% block head %}{% endblock %}
  {% if renderBlocking %}
    <link rel="stylesheet" href="/test/css/styles.css?delay={{ renderBlocking }}">
  {% endif %}
  <style>
    * {
      box-sizing: border-box;
    }
    *[hidden] {
      visibility: hidden;
    }
    body {
      font: 1em/1.5 sans-serif;
      margin: 0;
    }
    main {
      border: 1px solid transparent; /* Prevent margin collapsing */
      min-height: 100vh;
      padding: 0 1em;
      position: relative;
      width: 100%;
    }
  </style>
</head>
<body>
  <main>
    {% block content %}{% endblock %}
  </main>
  {% if delayDCL %}
    <script defer src="/test/script/defer.js?delay={{ delayDCL }}"></script>
  {% endif %}

  {% if delayLoad %}
    <script async src="/test/script/async.js?delay={{ delayLoad }}"></script>
  {% endif %}