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<!DOCTYPE html>
<meta charset="utf-8">
<link rel="author" title="Oriol Brufau" href="obrufau@igalia.com">
<link rel="help" href="https://www.w3.org/TR/CSS22/box.html#collapsing-margins">
<link rel="help" href="https://github.com/w3c/csswg-drafts/issues/8919">
<link rel="help" href="https://github.com/servo/servo/pull/32064">
<meta name="assert" content="
Margins can collapse through when the used height is zero, regardless of the computed values
of `height`, `min-height` and `max-height`.
Note that this test uses sizing values which didn't exist in CSS2, but since the expectations
only depend on the used height, the test can still pass on implementations that don't support
these values.
">
<style>
.before, .after {
overflow: hidden;
}
.wrapper {
border: 1px solid;
margin-bottom: 2em;
}
.test {
margin: 50px;
}
</style>
<div id="log"></div>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
let testcases = [
// Tests for `height`
{ height: "auto" },
{ height: "0px" },
{ height: "1px" },
{ height: "0%", parentHeight: "auto" },
{ height: "0%", parentHeight: "0px" },
{ height: "0%", parentHeight: "100px" },
{ height: "1%", parentHeight: "auto" },
{ height: "1%", parentHeight: "0px" },
{ height: "1%", parentHeight: "100px" },
{ height: "calc(0px + 0%)", parentHeight: "auto" },
{ height: "calc(0px + 0%)", parentHeight: "0px" },
{ height: "calc(0px + 0%)", parentHeight: "100px" },
{ height: "calc(0px + 1%)", parentHeight: "auto" },
{ height: "calc(0px + 1%)", parentHeight: "0px" },
{ height: "calc(0px + 1%)", parentHeight: "100px" },
{ height: "calc(1px + 0%)", parentHeight: "auto" },
{ height: "calc(1px + 0%)", parentHeight: "0px" },
{ height: "calc(1px + 0%)", parentHeight: "100px" },
{ height: "calc(1px + 1%)", parentHeight: "auto" },
{ height: "calc(1px + 1%)", parentHeight: "0px" },
{ height: "calc(1px + 1%)", parentHeight: "100px" },
{ height: "stretch", parentHeight: "auto" },
{ height: "stretch", parentHeight: "0px" },
{ height: "stretch", parentHeight: "100px" },
// Tests for `min-height` (with `height: auto`)
{ minHeight: "auto" },
{ minHeight: "0px" },
{ minHeight: "1px" },
{ minHeight: "0%", parentHeight: "auto" },
{ minHeight: "0%", parentHeight: "0px" },
{ minHeight: "0%", parentHeight: "100px" },
{ minHeight: "1%", parentHeight: "auto" },
{ minHeight: "1%", parentHeight: "0px" },
{ minHeight: "1%", parentHeight: "100px" },
{ minHeight: "calc(0px + 0%)", parentHeight: "auto" },
{ minHeight: "calc(0px + 0%)", parentHeight: "0px" },
{ minHeight: "calc(0px + 0%)", parentHeight: "100px" },
{ minHeight: "calc(0px + 1%)", parentHeight: "auto" },
{ minHeight: "calc(0px + 1%)", parentHeight: "0px" },
{ minHeight: "calc(0px + 1%)", parentHeight: "100px" },
{ minHeight: "calc(1px + 0%)", parentHeight: "auto" },
{ minHeight: "calc(1px + 0%)", parentHeight: "0px" },
{ minHeight: "calc(1px + 0%)", parentHeight: "100px" },
{ minHeight: "calc(1px + 1%)", parentHeight: "auto" },
{ minHeight: "calc(1px + 1%)", parentHeight: "0px" },
{ minHeight: "calc(1px + 1%)", parentHeight: "100px" },
{ minHeight: "stretch", parentHeight: "auto" },
{ minHeight: "stretch", parentHeight: "0px" },
{ minHeight: "stretch", parentHeight: "100px" },
// Tests for `max-height` (with `height: 1px`)
{ height: "1px", maxHeight: "none" },
{ height: "1px", maxHeight: "0px" },
{ height: "1px", maxHeight: "1px" },
{ height: "1px", maxHeight: "0%", parentHeight: "auto" },
{ height: "1px", maxHeight: "0%", parentHeight: "0px" },
{ height: "1px", maxHeight: "0%", parentHeight: "100px" },
{ height: "1px", maxHeight: "1%", parentHeight: "auto" },
{ height: "1px", maxHeight: "1%", parentHeight: "0px" },
{ height: "1px", maxHeight: "1%", parentHeight: "100px" },
{ height: "1px", maxHeight: "calc(0px + 0%)", parentHeight: "auto" },
{ height: "1px", maxHeight: "calc(0px + 0%)", parentHeight: "0px" },
{ height: "1px", maxHeight: "calc(0px + 0%)", parentHeight: "100px" },
{ height: "1px", maxHeight: "calc(0px + 1%)", parentHeight: "auto" },
{ height: "1px", maxHeight: "calc(0px + 1%)", parentHeight: "0px" },
{ height: "1px", maxHeight: "calc(0px + 1%)", parentHeight: "100px" },
{ height: "1px", maxHeight: "calc(1px + 0%)", parentHeight: "auto" },
{ height: "1px", maxHeight: "calc(1px + 0%)", parentHeight: "0px" },
{ height: "1px", maxHeight: "calc(1px + 0%)", parentHeight: "100px" },
{ height: "1px", maxHeight: "calc(1px + 1%)", parentHeight: "auto" },
{ height: "1px", maxHeight: "calc(1px + 1%)", parentHeight: "0px" },
{ height: "1px", maxHeight: "calc(1px + 1%)", parentHeight: "100px" },
{ height: "1px", maxHeight: "stretch", parentHeight: "auto" },
{ height: "1px", maxHeight: "stretch", parentHeight: "0px" },
{ height: "1px", maxHeight: "stretch", parentHeight: "100px" },
];
// The checks below force layout, so as an optimization, generate all elements first.
let generatedData = testcases.map(testcase => {
let { height, minHeight, maxHeight, parentHeight, ...unrecognized } = testcase;
assert_array_equals(Object.keys(unrecognized), [], "No unrecognized key.");
let serialization = JSON.stringify(testcase);
let wrapper = document.createElement("div");
wrapper.className = "wrapper";
wrapper.style.height = parentHeight || "";
let before = document.createElement("div");
before.className = "before";
before.textContent = serialization;
let after = document.createElement("div");
after.className = "after";
let test = document.createElement("div");
test.className = "test";
test.style.height = height || "";
test.style.minHeight = minHeight || "";
test.style.maxHeight = maxHeight || "";
wrapper.append(before, test, after);
document.body.append(wrapper);
return { serialization, before, test, after };
});
function round(value) {
return Math.round(value * 10) / 10;
}
for (let data of generatedData) {
test(() => {
let { before, test, after } = data;
let height = round(test.getBoundingClientRect().height);
let marginSum = round(after.getBoundingClientRect().top - before.getBoundingClientRect().bottom) - height;
if (height === 0) {
assert_equals(marginSum, 50, "margins should collapse through");
} else {
assert_equals(marginSum, 100, "margins should NOT collapse through when height is " + height);
}
}, data.serialization);
}
</script>
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