cobalt/black_box_tests/testdata/preload_font.html

<!DOCTYPE html>

<head>
  <title>Font Loading After Preload Test</title>
  <style>
    @font-face {
      font-family: networkfont;
      src: url('test_font.ttf');
    }

    h1 {
      font-family: networkfont;
      color: #c50000;
    }
  </style>
  <script src='black_box_js_test_utils.js'></script>
</head>

<body>
  <h1>
    <span id="unique_id">ID element</span>
  </h1>
  <script>
    // 80.34375 is the size of "unique_id" in the designated web font.
    assertNotEqual(80.34375,
      document.getElementsByTagName('span').item(0).offsetWidth);

    function handleVisibilityChange() {
      // Visibility Change happens when Cobalt receives resume signal, check font every .1 sec.
      const font_loading_time_maximum_in_milliseconds = 1000;
      let time_elapsed = 0;
      let set_interval_id = setInterval(() => {
        if (80.34375 === document.getElementsByTagName('span').item(0).offsetWidth) {
          onEndTest();
          clearInterval(set_interval_id);
        } else if (time_elapsed >= font_loading_time_maximum_in_milliseconds) {
          notReached();
          clearInterval(set_interval_id);
        } else {
          time_elapsed += 100;
        }
      }, 100);
    }
    document.addEventListener("visibilitychange", handleVisibilityChange);
    setupFinished();
  </script>
</body>