Fix Vertical Layout

[JimBobSquarePants]

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Description

Fixes #429 by ensuring that we test against the substituted codepoint where possible. Also enhances CJK codepoint detection.

Copilot reviewed 12 out of 27 changed files in this pull request and generated 1 comment.

Files not reviewed (15)

• samples/DrawWithImageSharp/DrawWithImageSharp.csproj: Language not supported
• src/SixLabors.Fonts/Tables/AdvancedTypographic/GSub/LookupType4SubTable.cs: Evaluated as low risk
• src/SixLabors.Fonts/FontMetrics.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/General/CMap/CMapSubTable.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/AdvancedTypographic/Shapers/UniversalShaper.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/AdvancedTypographic/Shapers/IndicShaper.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/AdvancedTypographic/Shapers/HangulShaper.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/AdvancedTypographic/Shapers/DefaultShaper.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/AdvancedTypographic/GSub/LookupType8SubTable.cs: Evaluated as low risk
• src/SixLabors.Fonts/FileFontMetrics.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/AdvancedTypographic/GSub/LookupType3SubTable.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/AdvancedTypographic/GSub/LookupType1SubTable.cs: Evaluated as low risk
• src/SixLabors.Fonts/Tables/AdvancedTypographic/GSub/LookupType2SubTable.cs: Evaluated as low risk
• src/SixLabors.Fonts/GlyphSubstitutionCollection.cs: Evaluated as low risk
• src/SixLabors.Fonts/StreamFontMetrics.cs: Evaluated as low risk

Comments suppressed due to low confidence (2)

src/SixLabors.Fonts/GlyphPositioningCollection.cs:95

• The parameter name isVerticalSubstitution is inconsistent with other parts of the code. It should be renamed to isVertical.

out bool isVerticalSubstitution,

src/SixLabors.Fonts/Tables/General/CMap/Format14SubTable.cs:139

• Ensure that the behavior of TryGetCodePoint always returning false is covered by tests.

public override bool TryGetCodePoint(ushort glyphId, out CodePoint codePoint)

The logic for checking vertical substitutions using FeatureTags.VerticalAlternates, FeatureTags.VerticalAlternatesAndRotation, and FeatureTags.VerticalAlternatesForRotation is duplicated in multiple places. This logic should be refactored into a separate method to avoid duplication and potential inconsistencies.

Suggested change

	Tag vert = FeatureTags.VerticalAlternates;
	isVerticalSubstitution = CheckVerticalSubstitution(glyph.Data.AppliedFeatures);

[JimBobSquarePants]

Logic is applied within a loop with other tests. Cannot abstract.

[tocsoft]

looks good