css/css-sizing/animation/width-interpolation.html

<!DOCTYPE html>
<meta charset="UTF-8">
<title>width interpolation</title>
<link rel="help" href="https://drafts.csswg.org/css-sizing-3/#propdef-width">
<meta name="assert" content="width supports animation by computed value">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/css/support/interpolation-testcommon.js"></script>

<style>
.parent {
  width: 100px;
  overflow: visible;
}
.target {
  font-size: 16px;
  background-color: black;
  width: 10px;
  height: 10px;
}
.expected {
  background-color: green;
}
</style>

<body>
  <template id="target-template">
    <div class="container">
      <div class="target"></div>
    </div>
  </template>
</body>

<script>
test_interpolation({
  property: 'width',
  from: neutralKeyframe,
  to: '40px',
}, [
  {at: -0.3, expect: '1px'},
  {at: 0, expect: '10px'},
  {at: 0.3, expect: '19px'},
  {at: 0.6, expect: '28px'},
  {at: 1, expect: '40px'},
  {at: 1.5, expect: '55px'},
]);

test_no_interpolation({
  property: 'width',
  from: 'initial',
  to: '40px',
});

test_interpolation({
  property: 'width',
  from: 'inherit',
  to: '40px',
}, [
  {at: -0.3, expect: '118px'},
  {at: 0, expect: '100px'},
  {at: 0.3, expect: '82px'},
  {at: 0.6, expect: '64px'},
  {at: 1, expect: '40px'},
  {at: 1.5, expect: '10px'},
]);

test_no_interpolation({
  property: 'width',
  from: 'unset',
  to: '40px',
});

test_interpolation({
  property: 'width',
  from: '0px',
  to: '100px',
}, [
  {at: -0.3, expect: '0px'}, // CSS width can't be negative.
  {at: 0, expect: '0px'},
  {at: 0.3, expect: '30px'},
  {at: 0.6, expect: '60px'},
  {at: 1, expect: '100px'},
  {at: 1.5, expect: '150px'}
]);

test_interpolation({
  property: 'width',
  from: '10px',
  to: '100%'
}, [
  {at: -0.3, expect: '0px'}, // CSS width can't be negative.
  {at: 0, expect: '10px'},
  {at: 0.3, expect: '37px'},
  {at: 0.6, expect: '64px'},
  {at: 1, expect: '100px'},
  {at: 1.5, expect: '145px'}
]);

// The "vw" unit equals to 1% of the width of the viewport's initial containing
// block:
// https://developer.mozilla.org/en-US/docs/Web/CSS/length
function vw(x) {
    return (x * window.innerWidth / 100);
}

// In here, 16 is the font-size which is the value of 1em, and vw(10) is the
// value of 10vw. The calc here takes the "at" in the next interpolation test
// and computes the expected value.
function calc(x) {
    return Math.max(16 + (vw(10) - 16) * x, 0).toFixed(2) + "px";
}

test_interpolation({
    property: 'width',
    from: '1em',
    to: '10vw'
}, [
    {at: -0.3, expect: calc(-0.3)},
    {at: 0, expect: calc(0)},
    {at: 0.3, expect: calc(0.3)},
    {at: 0.6, expect: calc(0.6)},
    {at: 1, expect: calc(1)},
    {at: 1.5, expect: calc(1.5)}
]);
</script>
</body>