THotPDF GSUB Lookup

THotPDF GSUB Lookup – metody

THotPDF API reference

Dokumentuje API pro lookupy GSUB na úrovni schopností pro jednoduché, vícenásobné, alternativní, ligaturní, kontextové, řetězené kontextové, reverzně řetězené, kontextově-funkční a lokalizované substituce forem

Delphi syntax

function GetSingleSubstituteGlyph(InputGID: Word; const FeatureTag: AnsiString): Word;

function GetMultipleSubstituteGlyphs(InputGID: Word; const FeatureTag: AnsiString; var OutGIDs: TGSUBLookupArray): Boolean;

function GetAlternateGlyphCount(InputGID: Word; const FeatureTag: AnsiString): Integer;

function GetAlternateGlyph(InputGID: Word; const FeatureTag: AnsiString; AlternateIndex: Integer): Word;

function ApplyLigatureSubstitution(const InputGIDs: array of Word; StartIndex: Integer; const FeatureTag: AnsiString; out OutGID: Word; out ConsumedCount: Integer): Boolean;

function ApplyContextualSubst(const InputGIDs: array of Word; StartIndex: Integer; const FeatureTag: AnsiString; var OutGIDs: TGSUBLookupArray; out ConsumedLen: Integer): Boolean;

function ApplyReverseChainedContextualSubst(const InputGIDs: array of Word; StartIndex: Integer; const FeatureTag: AnsiString; out OutGID: Word): Boolean;

function ApplyGSUBContextualFeature(const Wide: UnicodeString; const AFeatureTag: AnsiString): UnicodeString;

function ApplyLocalizedForms(const Wide: UnicodeString): UnicodeString;

Covered APIs

API	Poznámky k použití
`GetSingleSubstituteGlyph`	Queries GSUB LookupType 1 single substitution and returns the input GID when no match exists
`GetMultipleSubstituteGlyphs`	Queries GSUB LookupType 2 multiple substitution and returns the replacement glyph sequence
`GetAlternateGlyphCount`	Counts GSUB LookupType 3 alternate glyphs for a covered input glyph
`GetAlternateGlyph`	Returns a selected alternate glyph by zero-based alternate index
`ApplyLigatureSubstitution`	Queries GSUB LookupType 4 ligature substitution for a glyph run starting at a specific index
`ApplyContextualSubst`	Applies GSUB contextual or chained contextual substitution where a rule can replace a run segment
`ApplyReverseChainedContextualSubst`	Queries GSUB reverse chained contextual single substitution for right-to-left compatible shaping rules
`ApplyGSUBContextualFeature`	Applies a named GSUB contextual feature such as rclt or calt to a Unicode run and maps substitutions safely
`ApplyLocalizedForms`	Applies GSUB locl substitutions under the active script and language while preserving text extraction mappings
`MarkUnicodeGlyphUsed`	Adds a returned substitute GID to the embedded font subset closure
`sfContextualAlternates`	Applies required contextual alternates through the rclt-capable GSUB contextual lookup path
`sfLocalizedForms`	Applies GSUB locl localized-form substitutions under the active script and language

Poznámky k použití

These methods answer what the font's GSUB table would do. ApplyGSUBContextualFeature is the shared path for contextual features such as rclt and calt; ApplyLocalizedForms applies locl under the active GSUB script and language. If the caller emits returned substitute GIDs manually, MarkUnicodeGlyphUsed or a synthetic-codepoint mapping must keep those glyphs inside the embedded subset and ToUnicode map

Viz také: OpenType GSUB Engine GSUB script and language methods ShapingFeatures Subset and mapping methods