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https://github.com/LadybirdBrowser/ladybird
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3353ec9663
The `:has()` pseudo-class requires traversing descendants (or siblings)
to find matches.
With this change we cache results keyed by `(Selector*, Element*)`
pairs. The cache is stored in `StyleComputer` and cleared at the start
of each style computation pass in `Document::update_style()`.
When `:has()` uses a descendant combinator and we find a match, we also
cache that all ancestors between the matching descendant and the
anchor match. For example with `div:has(.target)`:
```html
<div id="A"> <!-- checking :has(.target) here -->
<div id="B">
<div id="C">
<span class="target"/>
</div>
</div>
</div>
```
When we find `.target` while checking `div#A`, we also cache that
`div#B` and `div#C` match `:has(.target)` since they also contain
`.target`. Later when styling these elements, we get cache hits and skip
traversal.
36 lines
1.0 KiB
HTML
36 lines
1.0 KiB
HTML
<!DOCTYPE html>
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<style>
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div:has(.target) { --match: 1; }
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</style>
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<div id="root"></div>
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<script src="../include.js"></script>
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<script>
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test(() => {
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const root = document.getElementById("root");
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// Build nested structure: root > d0 > d1 > ... > d19 > span.target
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let current = root;
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for (let i = 0; i < 20; i++) {
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const div = document.createElement("div");
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div.id = `d${i}`;
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current.appendChild(div);
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current = div;
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}
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current.innerHTML = '<span class="target"></span>';
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// Force style computation
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document.body.offsetHeight;
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// All ancestors should match :has(.target)
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for (let i = 0; i < 20; i++) {
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const el = document.getElementById(`d${i}`);
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const val = getComputedStyle(el).getPropertyValue("--match").trim();
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if (val !== "1") {
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println(`FAIL: d${i} should match :has(.target)`);
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return;
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}
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}
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println("PASS");
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});
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</script>
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