Inherit dominant-baseline into nested <tspan> elements#1070
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`dominant-baseline` was listed in `is_non_inheritable`, so usvg only let a `<tspan>` pick up the value from its *direct* parent element. For a nested `<tspan>` whose immediate parent does not carry the property, the value of an ancestor `<text>` was therefore lost and the span fell back to `auto` (alphabetic baseline). The nested run then sat on a different baseline than its siblings — the "weird" positioning reported in linebender#864. `dominant-baseline` is actually an *inherited* property, unlike its siblings `alignment-baseline` and `baseline-shift`: - SVG 2 / CSS Inline Layout Module Level 3 define it with "Inherited: yes". https://www.w3.org/TR/SVG2/text.html#BaselineAlignmentProperties - Chromium marks it `inherited: true` (field group `svginherited`), while `alignment-baseline` and `baseline-shift` are not inherited: https://github.com/chromium/chromium/blob/main/third_party/blink/renderer/core/css/css_properties.json5 (`name: "dominant-baseline" ... inherited: true`) - Inkscape declares it as an inheriting `SPIEnum` (default `inherits = true`). Removing it from `is_non_inheritable` makes `find_attribute`/`resolve_inherit` walk the full ancestor chain, matching Chrome's rendering (verified by comparison) and the spec. Fixes linebender#864. Tests: - usvg: `nested_tspan_inherits_dominant_baseline` and the override variant assert the resolved baseline on the spans; they fail before the fix (`Auto` vs `TextAfterEdge`). - resvg: render test `text/dominant-baseline/inherited-through-nested-tspan` (reference PNG optimized with oxipng). All existing baseline tests are unchanged. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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dominant-baselinewas listed inis_non_inheritable, so usvg only let a<tspan>pick up the value from its direct parent element. For a nested<tspan>whose immediate parent does not carry the property, the value of an ancestor<text>was therefore lost and the span fell back toauto(alphabetic baseline). The nested run then sat on a different baseline than its siblings — the "weird" positioning reported in #864.dominant-baselineis actually an inherited property, unlike its siblingsalignment-baselineandbaseline-shift:inherited: true(field groupsvginherited), whilealignment-baselineandbaseline-shiftare not inherited: https://github.com/chromium/chromium/blob/main/third_party/blink/renderer/core/css/css_properties.json5 (name: "dominant-baseline" ... inherited: true)SPIEnum(defaultinherits = true).Removing it from
is_non_inheritablemakesfind_attribute/resolve_inheritwalk the full ancestor chain, matching Chrome's rendering (verified by comparison) and the spec.Fixes #864.
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