0863153acd
Add parent-first-child top and parent-last-child bottom margin collapsing using a two-level approach (Level A shifts child inside parent, Level B adjusts grandparent for effective collapsed margin). Fix pre-existing bug in shift_subtree_x that incorrectly skipped absolute/fixed children. Extract shared MARGIN_EPSILON constant, add 9 unit tests and 4 golden tests (209-212), promote 31 WPT tests to pass. Includes code review fixes: pub(crate) visibility for is_root_element, known-limitation docs, and inline-content shift test coverage. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
24 lines
732 B
HTML
24 lines
732 B
HTML
<!DOCTYPE html>
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<!-- NOTE: This tests a 3-level nested parent-child margin collapsing chain.
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Per CSS 2.1 §8.3.1, all three margins (10, 20, 30) should collapse to 30px.
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Known limitation: our implementation propagates one level at a time, so
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deeper chains may produce partially correct results. This golden captures
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the current (correct for this case) behavior. -->
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<html>
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<head>
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<style>
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body { margin: 0; }
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.outer { margin-top: 10px; background: lightblue; }
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.middle { margin-top: 20px; background: lightgreen; }
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.inner { margin-top: 30px; height: 50px; background: lightyellow; }
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</style>
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</head>
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<body>
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<div class="outer">
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<div class="middle">
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<div class="inner"></div>
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</div>
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</div>
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</body>
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</html>
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