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Merged
JimBobSquarePants merged 1 commit into from
Nov 27, 2025
Merged

Use correct font metrics for fallback glyph substitutions #485

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2 changes: 1 addition & 1 deletion src/SixLabors.Fonts/GlyphSubstitutionCollection.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ internal sealed class GlyphSubstitutionCollection : IGlyphShapingCollection
/// <summary>
/// Contains a map the index of a map within the collection, non-sequential codepoint offsets, and their glyph ids.
/// </summary>
private readonly List<OffsetGlyphDataPair> glyphs = new();
private readonly List<OffsetGlyphDataPair> glyphs = [];

/// <summary>
/// Initializes a new instance of the <see cref="GlyphSubstitutionCollection"/> class.
Expand Down
2 changes: 1 addition & 1 deletion src/SixLabors.Fonts/Tables/AdvancedTypographic/GPosTable.cs
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Expand Up @@ -155,7 +155,7 @@ current is not ScriptClass.Common and not ScriptClass.Unknown and not ScriptClas
}

Tag unicodeScriptTag = this.GetUnicodeScriptTag(current);
BaseShaper shaper = ShaperFactory.Create(current, unicodeScriptTag, collection.TextOptions);
BaseShaper shaper = ShaperFactory.Create(current, unicodeScriptTag, fontMetrics, collection.TextOptions);

if (shaper.MarkZeroingMode == MarkZeroingMode.PreGPos)
{
Expand Down
2 changes: 1 addition & 1 deletion src/SixLabors.Fonts/Tables/AdvancedTypographic/GSubTable.cs
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Expand Up @@ -138,7 +138,7 @@ current is not ScriptClass.Common and not ScriptClass.Unknown and not ScriptClas
}

Tag unicodeScriptTag = this.GetUnicodeScriptTag(current);
BaseShaper shaper = ShaperFactory.Create(current, unicodeScriptTag, collection.TextOptions);
BaseShaper shaper = ShaperFactory.Create(current, unicodeScriptTag, fontMetrics, collection.TextOptions);

// Plan substitution features for each glyph.
// Shapers can adjust the count during initialization and feature processing so we must capture
Expand Down
45 changes: 19 additions & 26 deletions src/SixLabors.Fonts/Tables/AdvancedTypographic/Shapers/HangulShaper.cs
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Expand Up @@ -64,10 +64,11 @@ internal sealed class HangulShaper : DefaultShaper
{ new byte[] { None, 0 }, new byte[] { None, 1 }, new byte[] { None, 0 }, new byte[] { None, 0 }, new byte[] { Decompose, 2 }, new byte[] { Decompose, 3 }, new byte[] { ToneMark, 0 } },
};

public HangulShaper(ScriptClass script, TextOptions textOptions)
private readonly FontMetrics fontMetrics;

public HangulShaper(ScriptClass script, TextOptions textOptions, FontMetrics fontMetrics)
: base(script, MarkZeroingMode.None, textOptions)
{
}
=> this.fontMetrics = fontMetrics;

/// <inheritdoc/>
protected override void PlanFeatures(IGlyphShapingCollection collection, int index, int count)
Expand Down Expand Up @@ -121,13 +122,13 @@ protected override void AssignFeatures(IGlyphShapingCollection collection, int i
case Compose:

// Found a decomposed syllable. Try to compose if supported by the font.
i = this.ComposeGlyph(substitutionCollection, data, i, type);
i = this.ComposeGlyph(substitutionCollection, i, type);
break;

case ToneMark:

// Got a valid syllable, followed by a tone mark. Move the tone mark to the beginning of the syllable.
ReOrderToneMark(substitutionCollection, data, i);
this.ReOrderToneMark(substitutionCollection, data, i);
break;

case Invalid:
Expand Down Expand Up @@ -172,8 +173,6 @@ protected override void AssignFeatures(IGlyphShapingCollection collection, int i
collection.EnableShapingFeature(i, VjmoTag);
collection.EnableShapingFeature(i, TjmoTag);
break;
default:
break;
}
}
}
Expand Down Expand Up @@ -216,7 +215,7 @@ private int DecomposeGlyph(GlyphSubstitutionCollection collection, GlyphShapingD
int l = (LBase + (s / VCount)) | 0;
int v = VBase + (s % VCount);

FontMetrics metrics = data.TextRun.Font!.FontMetrics;
FontMetrics metrics = this.fontMetrics;

// Don't decompose if all of the components are not available
if (!metrics.TryGetGlyphId(new(l), out ushort ljmo) ||
Expand Down Expand Up @@ -252,7 +251,7 @@ private int DecomposeGlyph(GlyphSubstitutionCollection collection, GlyphShapingD
return index + 2;
}

private int ComposeGlyph(GlyphSubstitutionCollection collection, GlyphShapingData data, int index, int type)
private int ComposeGlyph(GlyphSubstitutionCollection collection, int index, int type)
{
if (index == 0)
{
Expand Down Expand Up @@ -306,8 +305,7 @@ private int ComposeGlyph(GlyphSubstitutionCollection collection, GlyphShapingDat

// Replace with a composed glyph if supported by the font,
// otherwise apply the proper OpenType features to each component.
FontMetrics metrics = data.TextRun.Font!.FontMetrics;
if (metrics.TryGetGlyphId(s, out ushort id))
if (this.fontMetrics.TryGetGlyphId(s, out ushort id))
{
int del = prevType == V ? 3 : 2;
int idx = index - del + 1;
Expand Down Expand Up @@ -338,15 +336,14 @@ private int ComposeGlyph(GlyphSubstitutionCollection collection, GlyphShapingDat
// Sequence was originally <L,V>, which got combined earlier.
// Either the T was non-combining, or the LVT glyph wasn't supported.
// Decompose the glyph again and apply OT features.
data = collection[index - 1];
this.DecomposeGlyph(collection, data, index - 1);
this.DecomposeGlyph(collection, collection[index - 1], index - 1);
return index + 1;
}

return index;
}

private static void ReOrderToneMark(GlyphSubstitutionCollection collection, GlyphShapingData data, int index)
private void ReOrderToneMark(GlyphSubstitutionCollection collection, GlyphShapingData data, int index)
{
if (index == 0)
{
Expand All @@ -355,17 +352,15 @@ private static void ReOrderToneMark(GlyphSubstitutionCollection collection, Glyp

// Move tone mark to the beginning of the previous syllable, unless it is zero width
// We don't have access to the glyphs metrics as an array when substituting so we have to loop.
FontMetrics fontMetrics = data.TextRun.Font!.FontMetrics;
FontMetrics fontMetrics = this.fontMetrics;
TextAttributes textAttributes = data.TextRun.TextAttributes;
TextDecorations textDecorations = data.TextRun.TextDecorations;
LayoutMode layoutMode = collection.TextOptions.LayoutMode;
ColorFontSupport colorFontSupport = collection.TextOptions.ColorFontSupport;
if (fontMetrics.TryGetGlyphMetrics(data.CodePoint, textAttributes, textDecorations, layoutMode, colorFontSupport, out GlyphMetrics? metrics))
if (fontMetrics.TryGetGlyphMetrics(data.CodePoint, textAttributes, textDecorations, layoutMode, colorFontSupport, out GlyphMetrics? metrics)
&& metrics.AdvanceWidth == 0)
{
if (metrics.AdvanceWidth == 0)
{
return;
}
return;
}

GlyphShapingData prev = collection[index - 1];
Expand All @@ -376,20 +371,18 @@ private static void ReOrderToneMark(GlyphSubstitutionCollection collection, Glyp
private int InsertDottedCircle(GlyphSubstitutionCollection collection, GlyphShapingData data, int index)
{
bool after = false;
FontMetrics fontMetrics = data.TextRun.Font!.FontMetrics;
FontMetrics fontMetrics = this.fontMetrics;

if (fontMetrics.TryGetGlyphId(new(DottedCircle), out ushort id))
{
TextAttributes textAttributes = data.TextRun.TextAttributes;
TextDecorations textDecorations = data.TextRun.TextDecorations;
LayoutMode layoutMode = collection.TextOptions.LayoutMode;
ColorFontSupport colorFontSupport = collection.TextOptions.ColorFontSupport;
if (fontMetrics.TryGetGlyphMetrics(data.CodePoint, textAttributes, textDecorations, layoutMode, colorFontSupport, out GlyphMetrics? metrics))
if (fontMetrics.TryGetGlyphMetrics(data.CodePoint, textAttributes, textDecorations, layoutMode, colorFontSupport, out GlyphMetrics? metrics)
&& metrics.AdvanceWidth != 0)
{
if (metrics.AdvanceWidth != 0)
{
after = true;
}
after = true;
}

// If the tone mark is zero width, insert the dotted circle before, otherwise after
Expand Down
67 changes: 29 additions & 38 deletions src/SixLabors.Fonts/Tables/AdvancedTypographic/Shapers/IndicShaper.cs
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Expand Up @@ -44,13 +44,15 @@ internal sealed class IndicShaper : DefaultShaper
private const int DottedCircle = 0x25cc;

private readonly TextOptions textOptions;
private readonly FontMetrics fontMetrics;
private ShapingConfiguration indicConfiguration;
private readonly bool isOldSpec;

public IndicShaper(ScriptClass script, Tag unicodeScriptTag, TextOptions textOptions)
public IndicShaper(ScriptClass script, Tag unicodeScriptTag, TextOptions textOptions, FontMetrics fontMetrics)
: base(script, MarkZeroingMode.None, textOptions)
{
this.textOptions = textOptions;
this.fontMetrics = fontMetrics;

if (IndicConfigurations.TryGetValue(script, out ShapingConfiguration value))
{
Expand Down Expand Up @@ -101,23 +103,24 @@ protected override void AssignFeatures(IGlyphShapingCollection collection, int i
return;
}

FontMetrics fontMetrics = this.fontMetrics;

// Decompose split matras
Span<ushort> buffer = stackalloc ushort[16];
int end = index + count;
for (int i = end - 1; i >= 0; i--)
{
GlyphShapingData data = substitutionCollection[i];
FontMetrics fontMetrics = data.TextRun.Font!.FontMetrics;

if ((Decompositions.TryGetValue(data.CodePoint.Value, out int[]? decompositions) ||
UniversalShapingData.Decompositions.TryGetValue(data.CodePoint.Value, out decompositions)) &&
decompositions != null)
{
Span<ushort> ids = buffer[..decompositions.Length];
for (int j = 0; j < decompositions.Length; j++)
{
// Font should always contain the decomposed glyph.
fontMetrics.TryGetGlyphId(new CodePoint(decompositions[j]), out ushort id);
// Font should always contain the decomposed glyph since the shaper
// is assigned based on features supported by the font.
_ = fontMetrics.TryGetGlyphId(new CodePoint(decompositions[j]), out ushort id);
ids[j] = id;
}

Expand Down Expand Up @@ -207,23 +210,22 @@ private void InitialReorder(IGlyphShapingCollection collection, int index, int c
Span<GlyphShapingData> tempBuffer = new GlyphShapingData[3];

ShapingConfiguration indicConfiguration = this.indicConfiguration;
for (int i = 0; i < count; i++)
{
GlyphShapingData data = substitutionCollection[i + index];
FontMetrics fontMetrics = data.TextRun.Font!.FontMetrics;
FontMetrics fontMetrics = this.fontMetrics;
CodePoint viramaPoint = new(indicConfiguration.Virama);

fontMetrics.TryGetGlyphId(new(0x0020), out ushort spc);

IndicShapingEngineInfo? info = data.IndicShapingEngineInfo;
if (info?.Position == Positions.Base_C)
if (fontMetrics.TryGetGlyphId(viramaPoint, out ushort viramaId))
{
for (int i = 0; i < count; i++)
{
CodePoint cp = new(indicConfiguration.Virama);
if (fontMetrics.TryGetGlyphId(cp, out ushort id))
GlyphShapingData data = substitutionCollection[i + index];
IndicShapingEngineInfo? info = data.IndicShapingEngineInfo;

if (info?.Position == Positions.Base_C)
{
GlyphShapingData virama = new(data, false)
{
GlyphId = id,
CodePoint = cp
GlyphId = viramaId,
CodePoint = viramaPoint
};

tempBuffer[2] = virama;
Expand All @@ -235,6 +237,8 @@ private void InitialReorder(IGlyphShapingCollection collection, int index, int c
}
}

bool hasDottedCircle = fontMetrics.TryGetGlyphId(new(DottedCircle), out ushort circleId);
_ = fontMetrics.TryGetGSubTable(out GSubTable? gSubTable);
int max = index + count;
int start = index;
int end = NextSyllable(substitutionCollection, index, max);
Expand All @@ -250,13 +254,7 @@ private void InitialReorder(IGlyphShapingCollection collection, int index, int c
goto Increment;
}

FontMetrics fontMetrics = data.TextRun.Font!.FontMetrics;
if (!fontMetrics.TryGetGSubTable(out GSubTable? gSubTable))
{
break;
}

if (dataInfo != null && type == "broken_cluster" && fontMetrics.TryGetGlyphId(new(DottedCircle), out ushort id))
if (dataInfo != null && hasDottedCircle && type == "broken_cluster")
{
// Insert after possible Repha.
int i = start;
Expand All @@ -272,7 +270,7 @@ private void InitialReorder(IGlyphShapingCollection collection, int index, int c
}

glyphs[0] = current.GlyphId;
glyphs[1] = id;
glyphs[1] = circleId;

substitutionCollection.Replace(i, glyphs, FeatureTags.GlyphCompositionDecomposition);

Expand Down Expand Up @@ -303,7 +301,7 @@ private void InitialReorder(IGlyphShapingCollection collection, int index, int c
// base consonants.
if (start + 3 <= end &&
indicConfiguration.RephPosition != Positions.Ra_To_Become_Reph &&
gSubTable.TryGetFeatureLookups(in RphfTag, this.ScriptClass, out _) &&
gSubTable?.TryGetFeatureLookups(in RphfTag, this.ScriptClass, out _) == true &&
((indicConfiguration.RephMode == RephMode.Implicit && !IsJoiner(substitutionCollection[start + 2])) ||
(indicConfiguration.RephMode == RephMode.Explicit && substitutionCollection[start + 2].IndicShapingEngineInfo?.Category == Categories.ZWJ)))
{
Expand Down Expand Up @@ -692,7 +690,7 @@ private void InitialReorder(IGlyphShapingCollection collection, int index, int c

const int prefLen = 2;
if (basePosition + prefLen < end &&
gSubTable.TryGetFeatureLookups(in PrefTag, this.ScriptClass, out _))
gSubTable?.TryGetFeatureLookups(in PrefTag, this.ScriptClass, out _) == true)
{
// Find a Halant,Ra sequence and mark it for pre-base reordering processing.
for (int i = basePosition + 1; i + prefLen - 1 < end; i++)
Expand Down Expand Up @@ -790,9 +788,7 @@ private bool WouldSubstitute(GlyphSubstitutionCollection collection, in Tag feat
collection.EnableShapingFeature(i, featureTag);
}

GlyphShapingData data = buffer[0];
FontMetrics fontMetrics = data.TextRun.Font!.FontMetrics;

FontMetrics fontMetrics = this.fontMetrics;
if (fontMetrics.TryGetGSubTable(out GSubTable? gSubTable))
{
const int index = 0;
Expand Down Expand Up @@ -865,6 +861,8 @@ private void FinalReorder(IGlyphShapingCollection collection, int index, int cou
int max = index + count;
int start = index;
int end = NextSyllable(substitutionCollection, index, max);
FontMetrics fontMetrics = this.fontMetrics;
_ = fontMetrics.TryGetGSubTable(out GSubTable? gSubTable);
while (start < max)
{
// 4. Final reordering:
Expand All @@ -873,14 +871,7 @@ private void FinalReorder(IGlyphShapingCollection collection, int index, int cou
// applied (see below), the shaping engine performs some final glyph
// reordering before applying all the remaining font features to the entire
// cluster.
GlyphShapingData data = substitutionCollection[start];
FontMetrics fontMetrics = data.TextRun.Font!.FontMetrics;
if (!fontMetrics.TryGetGSubTable(out GSubTable? gSubTable))
{
break;
}

bool tryPref = gSubTable.TryGetFeatureLookups(in PrefTag, this.ScriptClass, out _);
bool tryPref = gSubTable?.TryGetFeatureLookups(in PrefTag, this.ScriptClass, out _) == true;

// Find base consonant again.
int basePosition = start;
Expand Down
17 changes: 11 additions & 6 deletions src/SixLabors.Fonts/Tables/AdvancedTypographic/Shapers/ShaperFactory.cs
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Expand Up @@ -8,13 +8,18 @@ namespace SixLabors.Fonts.Tables.AdvancedTypographic.Shapers;
internal static class ShaperFactory
{
/// <summary>
/// Creates a Shaper based on the given script language.
/// Creates a shaper based on the given script language.
/// </summary>
/// <param name="script">The script language.</param>
/// <param name="unicodeScriptTag">The unicode script tag found in the font matching the script.</param>
/// <param name="textOptions">The text options.</param>
/// <param name="fontMetrics">The current font metrics.</param>
/// <param name="textOptions">The global text options.</param>
/// <returns>A shaper for the given script.</returns>
public static BaseShaper Create(ScriptClass script, Tag unicodeScriptTag, TextOptions textOptions)
public static BaseShaper Create(
ScriptClass script,
Tag unicodeScriptTag,
FontMetrics fontMetrics,
TextOptions textOptions)
=> script switch
{
// Arabic
Expand All @@ -28,7 +33,7 @@ or ScriptClass.Manichaean
or ScriptClass.PsalterPahlavi => new ArabicShaper(script, textOptions),

// Hangul
ScriptClass.Hangul => new HangulShaper(script, textOptions),
ScriptClass.Hangul => new HangulShaper(script, textOptions, fontMetrics),

// Indic
ScriptClass.Bengali
Expand All @@ -40,7 +45,7 @@ or ScriptClass.Malayalam
or ScriptClass.Oriya
or ScriptClass.Tamil
or ScriptClass.Telugu
or ScriptClass.Khmer => new IndicShaper(script, unicodeScriptTag, textOptions),
or ScriptClass.Khmer => new IndicShaper(script, unicodeScriptTag, textOptions, fontMetrics),

// Universal
ScriptClass.Balinese
Expand Down Expand Up @@ -82,7 +87,7 @@ or ScriptClass.Takri
or ScriptClass.Tibetan
or ScriptClass.Tifinagh
or ScriptClass.Tirhuta
=> new UniversalShaper(script, textOptions),
=> new UniversalShaper(script, textOptions, fontMetrics),
_ => new DefaultShaper(script, textOptions),
};
}
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