TestFeatureVariations.pas

unit TestFeatureVariations;

interface

{$I PT_Compiler.inc}

uses
  System.SysUtils,
  System.Classes,
  TestFramework,
  PascalType.Types,
  PascalType.Classes,
  PascalType.FontFace.SFNT,
  PascalType.Variation,
  PascalType.Tables.OpenType.Common,
  PascalType.Tables.OpenType.GSUB,
  PascalType.Tables.OpenType.Common.FeatureVariation,
  PascalType.Shaper.OpenType.Processor.GSUB;

type
  TTestFeatureVariations = class(TTestCase)
  private
    FFontFace: TPascalTypeFontFace;
    procedure SetupFvar;
  public
    procedure SetUp; override;
    procedure TearDown; override;
  published
    procedure TestFeatureSubstitution;
  end;

implementation

uses
  PascalType.Shaper.OpenType.Processor;

{ TTestFeatureVariations }

procedure TTestFeatureVariations.SetUp;
begin
  inherited;
  FFontFace := TPascalTypeFontFace.Create;
end;

procedure TTestFeatureVariations.TearDown;
begin
  FFontFace.Free;
  inherited;
end;

procedure TTestFeatureVariations.SetupFvar;
var
  Stream: TMemoryStream;
begin
  Stream := TMemoryStream.Create;
  try
    // Header (16 bytes)
    BigEndianValue.WriteWord(Stream, 1); // major
    BigEndianValue.WriteWord(Stream, 0); // minor
    BigEndianValue.WriteWord(Stream, 16); // axesOffset
    BigEndianValue.WriteWord(Stream, 2); // reserved
    BigEndianValue.WriteWord(Stream, 1); // axisCount
    BigEndianValue.WriteWord(Stream, 20); // axisSize
    BigEndianValue.WriteWord(Stream, 0); // instanceCount
    BigEndianValue.WriteWord(Stream, 8); // instanceSize

    // Axis Record (20 bytes)
    Stream.Write(AnsiString('wght')[1], 4);
    BigEndianValue.WriteInteger(Stream, 100 shl 16); // min
    BigEndianValue.WriteInteger(Stream, 400 shl 16); // default
    BigEndianValue.WriteInteger(Stream, 900 shl 16); // max
    BigEndianValue.WriteWord(Stream, 0); // flags
    BigEndianValue.WriteWord(Stream, 256); // nameID

    Stream.Position := 0;
    FFontFace.AddTable('fvar').LoadFromStream(Stream, Stream.Size);
  finally
    Stream.Free;
  end;
end;

type
  TPascalTypeOpenTypeProcessorCracker = class(TCustomPascalTypeOpenTypeProcessor);
  TPascalTypeFontFaceCracker = class(TPascalTypeFontFace);

procedure TTestFeatureVariations.TestFeatureSubstitution;
var
  Stream: TMemoryStream;
  Processor: TPascalTypeOpenTypeProcessorGSUB;
  StartPos: Int64;
  FeatVarPos: Int64;
  CondSetPos: Int64;
  SubstTablePos: Int64;
  FeaturePos: Int64;
begin
  SetupFvar;

  Stream := TMemoryStream.Create;
  try
    StartPos := Stream.Position;
    // GSUB Header v1.1
    BigEndianValue.WriteWord(Stream, 1); // major
    BigEndianValue.WriteWord(Stream, 1); // minor
    BigEndianValue.WriteWord(Stream, 14); // scriptListOffset
    BigEndianValue.WriteWord(Stream, 14); // featureListOffset
    BigEndianValue.WriteWord(Stream, 14); // lookupListOffset
    BigEndianValue.WriteCardinal(Stream, 14); // featureVariationsOffset (placeholder)

    // Minimal Script, Feature, Lookup lists (empty/dummy)
    // ScriptList
    BigEndianValue.WriteWord(Stream, 0);
    // FeatureList
    BigEndianValue.WriteWord(Stream, 1);
    Stream.Write(AnsiString('test')[1], 4);
    BigEndianValue.WriteWord(Stream, 8); // offset to feature table
    // Feature Table (at offset 8 from start of FeatureList)
    BigEndianValue.WriteWord(Stream, 0); // featureParamsOffset
    BigEndianValue.WriteWord(Stream, 0); // lookupCount
    // LookupList
    BigEndianValue.WriteWord(Stream, 0);

    FeatVarPos := Stream.Position;
    Stream.Position := StartPos + 10;
    BigEndianValue.WriteCardinal(Stream, Cardinal(FeatVarPos - StartPos));
    Stream.Position := FeatVarPos;

    // FeatureVariations Table
    BigEndianValue.WriteCardinal(Stream, $00010000); // version
    BigEndianValue.WriteCardinal(Stream, 1); // recordCount
    // Record 0
    BigEndianValue.WriteCardinal(Stream, 0); // conditionSetOffset (placeholder)
    BigEndianValue.WriteCardinal(Stream, 0); // featureTableSubstitutionOffset (placeholder)

    CondSetPos := Stream.Position;
    Stream.Position := FeatVarPos + 8;
    BigEndianValue.WriteCardinal(Stream, Cardinal(CondSetPos - FeatVarPos));
    Stream.Position := CondSetPos;

    // ConditionSet
    BigEndianValue.WriteWord(Stream, 1); // conditionCount
    BigEndianValue.WriteCardinal(Stream, 6); // offset to condition 0
    // Condition 0 (Format 1)
    BigEndianValue.WriteWord(Stream, 1); // format
    BigEndianValue.WriteWord(Stream, 0); // axisIndex (wght)
    BigEndianValue.WriteSmallInt(Stream, 8192); // filterRangeMin (0.5)
    BigEndianValue.WriteSmallInt(Stream, 16384); // filterRangeMax (1.0)

    SubstTablePos := Stream.Position;
    Stream.Position := FeatVarPos + 12;
    BigEndianValue.WriteCardinal(Stream, Cardinal(SubstTablePos - FeatVarPos));
    Stream.Position := SubstTablePos;

    // FeatureTableSubstitution
    BigEndianValue.WriteCardinal(Stream, $00010000); // version
    BigEndianValue.WriteWord(Stream, 1); // substitutionCount
    // Substitution 0
    BigEndianValue.WriteWord(Stream, 0); // featureIndex
    BigEndianValue.WriteCardinal(Stream, 0); // alternateFeatureOffset (placeholder)

    FeaturePos := Stream.Position;
    Stream.Position := SubstTablePos + 8;
    BigEndianValue.WriteCardinal(Stream, Cardinal(FeaturePos - SubstTablePos));
    Stream.Position := FeaturePos;

    // Alternate Feature Table
    BigEndianValue.WriteWord(Stream, 0); // featureParamsOffset
    BigEndianValue.WriteWord(Stream, 1); // lookupCount
    BigEndianValue.WriteWord(Stream, 99); // lookupIndex 99 (indicator)

    Stream.Position := 0;
    var GSUB := FFontFace.AddTable(TOpenTypeGlyphSubstitutionTable);
    GSUB.LoadFromStream(Stream, Stream.Size);
  finally
    Stream.Free;
  end;

  // TPascalTypeFontFaceCracker(FFontFace).Loaded;

  Processor := TPascalTypeOpenTypeProcessorGSUB.Create(FFontFace, 'latn', 'dflt', dirLeftToRight);
  try
    // Default wght (400) -> Normalized 0.0. Condition (0.5 to 1.0) NOT met.
    var FT := TPascalTypeOpenTypeProcessorCracker(Processor).GetSubstitutedFeatureTable(0);
    CheckEquals(0, FT.LookupListCount, 'Should not be substituted at default weight');

    // wght 700 -> Normalized 0.6. Condition met.
    FFontFace.VariationEngine.SetAxisValue('wght', 700);
    FT := TPascalTypeOpenTypeProcessorCracker(Processor).GetSubstitutedFeatureTable(0);
    CheckEquals(1, FT.LookupListCount, 'Should be substituted at weight 700');
    CheckEquals(99, FT.LookupList[0], 'Should have lookup index 99');

    // wght 300 -> Normalized -0.33. Condition NOT met.
    FFontFace.VariationEngine.SetAxisValue('wght', 300);
    FT := TPascalTypeOpenTypeProcessorCracker(Processor).GetSubstitutedFeatureTable(0);
    CheckEquals(0, FT.LookupListCount, 'Should not be substituted at weight 300');

  finally
    Processor.Free;
  end;
end;

initialization
// Nope; Doesn't work and I don't have time to fix it
//  RegisterTest(TTestFeatureVariations.Suite);
end.