Bug 287629 – [GTK][WPE] <lang-attribute-affects-rendering.html> fails

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Deleted User]

https://github.com/web-platform-tests/wpt/blob/1a5b13545a/css/css-fonts/lang-attribute-affects-rendering.html

It only fails for GTK: https://wpt.fyi/results/css?label=master&product=chrome%5Bexperimental%5D&product=edge%5Bexperimental%5D&product=firefox%5Bexperimental%5D&product=safari%5Bexperimental%5D&product=webkitgtk&aligned&q=%2Fcss%2Fcss-fonts%2Flang-attribute-affects-rendering.html.

[Deleted User]

Some analysis, read the test-case for context:

- https://searchfox.org/wubkat/rev/eb60a003e2487c2a8f34aaf8ce8f5d5af280ed55/Source/WebCore/platform/graphics/ComplexTextController.cpp#358 is called for "fi".
- `m_font.fontDescription().computedLocale()` is "en" ("tr" for the -ref.html file). That's expected.
- `FontCascade::fontForCombiningCharacterSequence` (https://searchfox.org/wubkat/rev/eb60a003e2487c2a8f34aaf8ce8f5d5af280ed55/Source/WebCore/platform/graphics/FontCascade.h#208) corresponds to different implementations: https://searchfox.org/wubkat/search?q=fontForCombiningCharacterSequence&redirect=false
- Since the test passes for Safari, perhaps the implementation for Skia, which is used by GTK, is buggy: https://searchfox.org/wubkat/rev/eb60a003e2487c2a8f34aaf8ce8f5d5af280ed55/Source/WebCore/platform/graphics/skia/FontCascadeSkia.cpp#132

[Deleted User]

Continued analysis:

https://searchfox.org/wubkat/rev/dd523ddb28deecac34400360788b2ba9cee771af/Source/WebCore/platform/graphics/ComplexTextController.cpp#462 is called.

Safari and GTK use different implementations of that method.

The test passes with Safari. Presumably, because of
<https://searchfox.org/wubkat/rev/dd523ddb28deecac34400360788b2ba9cee771af/Source/WebCore/platform/graphics/coretext/ComplexTextControllerCoreText.mm#200>.

The bug/missing functionality for GTK is presumably in the GTK-specific implementation: <https://searchfox.org/wubkat/rev/dd523ddb28deecac34400360788b2ba9cee771af/Source/WebCore/platform/graphics/skia/ComplexTextControllerSkia.cpp#153>.

[Deleted User]

`hb_language_t` (https://harfbuzz.github.io/harfbuzz-hb-common.html#hb-language-t) might need to be set.

[Deleted User]

Pull request: https://github.com/WebKit/WebKit/pull/40761

[EWS]

Committed 291691@main (c30953f1f00c): <https://commits.webkit.org/291691@main>

Reviewed commits have been landed. Closing PR #40761 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/146381919>