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<!DOCTYPE html>
<title>Length unit 'ch' should be recalculated after loading a web font</title>
<link rel="help" href="https://www.w3.org/TR/css-values-4/#font-relative-lengths">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
.container {
font: 25px/1 "custom font", monospace;
}
.test {
width: 1ch;
}
</style>
<div class="container">
<div class="test"></div>
</div>
<div class="container" style="display: contents">
<div class="test"></div>
</div>
<div class="container" style="display: none">
<div class="test"></div>
</div>
<script>
function parseWidthInPx(element) {
const value = getComputedStyle(element).width;
if (!value.endsWith('px'))
return NaN;
return parseFloat(value);
}
const testCases = document.querySelectorAll('.test');
const asyncTests = [
async_test('ch in a normal div should be recalculated after loading a web font'),
async_test('ch in display:contents should be recalculated after loading a web font'),
async_test('ch in display:none should be recalculated after loading a web font')
];
// Before loading custom font, tests should be rendered with monospace
// fallback and have a '1ch' measurement much shorter than 25px.
for (let i = 0; i < testCases.length; ++i) {
asyncTests[i].step(() => {
const widthPx = parseWidthInPx(testCases[i]);
assert_less_than(widthPx, 24);
});
}
// Insert custom font into style sheet and load it
const customFont = new FontFace('custom font', 'url(/fonts/Ahem.ttf)');
document.fonts.add(customFont);
// After loading custom font, tests should be rendered with the custom font,
// which is Ahem, and have a '1ch' measurement that equals 25px.
customFont.load().then(
() => {
for (let i = 0; i < testCases.length; ++i) {
asyncTests[i].step(() => {
const widthPx = parseWidthInPx(testCases[i]);
assert_approx_equals(widthPx, 25, 0.1);
asyncTests[i].done();
});
}
},
() => {
for (let i = 0; i < testCases.length; ++i) {
asyncTests[i].step(() => {
assert_unreached('Failed to load font');
});
}
}
);
</script>
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