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Automatic update from web-platform-tests Support reverting to/from css-logical properties The properties defined by css-logical (and more generally surrogates) pose a hard problem for 'revert' in the StyleCascade, because declarations such as 'margin-bottom:revert' may actually need to revert to a different property in the previous origin (e.g. margin-block-end). An example is the h1 element, which is styled by html.css using css-logical properties. When the author then reverts using a corresponding physical property, we can't simply look up the cascaded value for that same physical property in the UA origin: we must be aware that the css-logical property won the cascade _at that level_. So when we we're applying an author declaration 'margin-bottom:revert', we have to find the *target property* for the revert, which is either margin-bottom (if that property won the cascade at the target origin), or the corresponding css-logical property. However, to find the target property, we need to know during the application of margin-bottom that a corresponding logical property (surrogate) needs to be taken into account. AutoSurrogateScope was created for this purpose, which sets (and resets) a "current surrogate" field on CascadeResolver. This current surrogate is used when resolving reverts, in order to find the correct target property. Also, we don't control the order in which physical/logical properties are applied. This means we could be applying the physical property first, which is unaware of any logical properties that should have been taken into account for revert. In other words, if we apply 'margin-bottom:revert' without the context of a "current surrogate" set, we'll fall back to unconditionally using margin-bottom as the target property, which may be incorrect if there also exists a logical property we'll get to later. This is why the force-reapply code exists: when both the physical and logical property exists in the cascade, the physical property must be applied (or re-applied) during AutoSurrogateScope, otherwise revert will not behave correctly. Bug: 579788 Change-Id: I864a4c9afdd94f130c42635d28d45c843d5fb617 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2130850 Commit-Queue: Anders Hartvoll Ruud <andruud@chromium.org> Reviewed-by: Rune Lillesveen <futhark@chromium.org> Cr-Commit-Position: refs/heads/master@{#756419} -- wpt-commits: a7b84565335bd31cbb265feca05cbef9cb4e999a wpt-pr: 22614
40 lines
1.3 KiB
HTML
40 lines
1.3 KiB
HTML
<!DOCTYPE html>
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<title>CSS Cascade: 'revert' in css-logical properties</title>
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<link rel="help" href="https://drafts.csswg.org/css-cascade/#default">
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<script src="/resources/testharness.js"></script>
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<script src="/resources/testharnessreport.js"></script>
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<style>
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#h1_physical {
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margin: 0px;
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margin: revert;
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}
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#h1_logical {
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margin: 0px;
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margin-inline-start: revert;
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margin-inline-end: revert;
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margin-block-start: revert;
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margin-block-end: revert;
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}
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</style>
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<h1 id=h1_physical></h1>
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<h1 id=h1_logical></h1>
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<h1 id=ref></h1>
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<script>
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test(function() {
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let actual = getComputedStyle(h1_physical).marginTop;
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let expected = getComputedStyle(ref).marginTop;
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// This test assumes that the UA style sheet sets a non-0px value on
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// <h1> elements:
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assert_not_equals(expected, '0px');
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assert_equals(actual, expected);
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}, 'The revert keyword works with physical properties');
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test(function() {
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let actual = getComputedStyle(h1_logical).marginTop;
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let expected = getComputedStyle(ref).marginTop;
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// This test assumes that the UA style sheet sets a non-0px value on
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// <h1> elements:
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assert_not_equals(expected, '0px');
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assert_equals(actual, expected);
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}, 'The revert keyword works with logical properties');
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</script>
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