css/css-cascade/layer-font-face-override.html

<!DOCTYPE html>
<title>Resolving @keyframe name conflicts with cascade layers</title>
<link rel="help" href="https://drafts.csswg.org/css-cascade-5/#layering">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#target {
  font-size: 20px;
  width: min-content;
}
</style>

<div id="target">Test</div>

<script>
// In all tests, width of #target should be 80px.

const testCases = [
  {
    title: '@font-face unlayered overrides layered',
    style: `
      #target {
        font-family: custom-font;
      }

      @font-face {
        font-family: custom-font;
        src: url('/fonts/Ahem.ttf');
      }

      @layer {
        @font-face {
          font-family: custom-font;
          src: url('/fonts/noto/noto-sans-v8-latin-regular.woff') format('woff');
        }
      }
    `
  },

  {
    title: '@font-face override between layers',
    style: `
      @layer base, override;

      #target {
        font-family: custom-font;
      }

      @layer override {
        @font-face {
          font-family: custom-font;
          src: url('/fonts/Ahem.ttf');
        }
      }

      @layer base {
        @font-face {
          font-family: custom-font;
          src: url('/fonts/noto/noto-sans-v8-latin-regular.woff') format('woff');
        }
      }
    `
  },

  {
    title: '@font-face override update with appended sheet 1',
    style: `
      @layer base, override;

      #target {
        font-family: custom-font;
      }

      @layer override {
        @font-face {
          font-family: custom-font;
          src: url('/fonts/Ahem.ttf');
        }
      }
    `,
    append: `
      @layer base {
        @font-face {
          font-family: custom-font;
          src: url('/fonts/noto/noto-sans-v8-latin-regular.woff') format('woff');
        }
      }
    `
  },

  {
    title: '@font-face override update with appended sheet 2',
    style: `
      @layer base, override;

      #target {
        font-family: custom-font;
      }

      @layer base {
        @font-face {
          font-family: custom-font;
          src: url('/fonts/noto/noto-sans-v8-latin-regular.woff') format('woff');
        }
      }
    `,
    append: `
      @layer override {
        @font-face {
          font-family: custom-font;
          src: url('/fonts/Ahem.ttf');
        }
      }
    `
  },
];

for (let testCase of testCases) {
  promise_test(async () => {
    var documentStyle = document.createElement('style');
    documentStyle.appendChild(document.createTextNode(testCase['style']));
    document.head.appendChild(documentStyle);

    var appendedStyle;
    if (testCase['append']) {
      document.body.offsetLeft;  // Force style update
      appendedStyle = document.createElement('style');
      appendedStyle.appendChild(document.createTextNode(testCase['append']));
      document.head.appendChild(appendedStyle);
    }

    await document.fonts.load('20px/1 custom-font');
    assert_equals(getComputedStyle(target).width, '80px');

    if (appendedStyle)
      appendedStyle.remove();
    documentStyle.remove();
  }, testCase['title']);
}
</script>