TextShaper

Appearance

Font Tables Reference ​

This document provides a brief overview of major OpenType and AAT font tables supported by TypeShaper.

Required Tables ​

HeadTable ​

Font header containing basic metadata.

Key Fields:

  • unitsPerEm: number - Font design units per em
  • flags: number - Font flags
  • created: Date - Creation date
  • modified: Date - Last modified date
  • xMin, yMin, xMax, yMax: number - Font bounding box
  • indexToLocFormat: number - Format of loca table (0 or 1)

MaxpTable ​

Maximum profile defining resource limits.

Key Fields:

  • numGlyphs: number - Number of glyphs in the font
  • maxPoints: number - Max points in non-composite glyph
  • maxContours: number - Max contours in non-composite glyph

HheaTable ​

Horizontal header with typographic metrics.

Key Fields:

  • ascender: number - Typographic ascender
  • descender: number - Typographic descender
  • lineGap: number - Line gap
  • advanceWidthMax: number - Maximum advance width
  • numberOfHMetrics: number - Number of hMetric entries

HmtxTable ​

Horizontal metrics for each glyph.

Access via:

typescript
const advance = font.advanceWidth(glyphId);
const lsb = font.leftSideBearing(glyphId);

CmapTable ​

Character to glyph mapping.

Access via:

typescript
const glyphId = font.glyphId(0x0041); // Unicode codepoint
const glyphId = font.glyphIdForChar("A"); // Character

OpenType Layout Tables ​

GdefTable ​

Glyph definition table classifying glyphs.

Glyph Classes:

  • Base - Base character
  • Ligature - Ligature glyph
  • Mark - Non-spacing mark
  • Component - Component of ligature

Features:

  • Glyph class definitions
  • Attachment points
  • Ligature caret positions
  • Mark attachment classes

GsubTable ​

Glyph substitution table for character-to-glyph transformations.

Lookup Types:

  1. Single - One-to-one substitution
  2. Multiple - One-to-many substitution
  3. Alternate - One-to-one from alternatives
  4. Ligature - Many-to-one substitution
  5. Context - Context-dependent substitution
  6. Chaining Context - Extended context substitution
  7. Extension - Extension mechanism
  8. Reverse Chaining - Right-to-left substitution

Common Features:

  • liga - Standard ligatures (fi, fl)
  • calt - Contextual alternates
  • ccmp - Glyph composition/decomposition
  • smcp - Small capitals
  • swsh - Swash forms

GposTable ​

Glyph positioning table for layout adjustments.

Lookup Types:

  1. Single - Adjust single glyph position
  2. Pair - Adjust glyph pair (kerning)
  3. Cursive - Cursive attachment
  4. MarkToBase - Attach mark to base
  5. MarkToLigature - Attach mark to ligature
  6. MarkToMark - Attach mark to mark
  7. Context - Context-dependent positioning
  8. Chaining Context - Extended context positioning
  9. Extension - Extension mechanism

Common Features:

  • kern - Kerning
  • mark - Mark positioning
  • mkmk - Mark-to-mark positioning
  • curs - Cursive attachment

KernTable ​

Legacy kerning table (pre-OpenType).

Access via:

typescript
import { getKernValue } from "typeshaper";

const kern = getKernValue(font.kern, glyph1, glyph2);

Variable Font Tables ​

FvarTable ​

Font variations defining variation axes.

Key Fields:

  • axes: VariationAxis[] - List of variation axes
  • instances: NamedInstance[] - Named instances

VariationAxis:

typescript
interface VariationAxis {
  tag: Tag;           // Axis tag (e.g., 'wght', 'wdth')
  minValue: number;   // Minimum value
  defaultValue: number; // Default value
  maxValue: number;   // Maximum value
  name: string;       // Axis name
}

GvarTable ​

Glyph variations for outline adjustments.

Usage:

typescript
const contours = font.getGlyphContoursWithVariation(glyphId, normalizedCoords);

HvarTable ​

Horizontal metrics variations.

Features:

  • Advance width deltas
  • Left side bearing deltas

Access via Face:

typescript
const face = new Face(font, { wght: 700 });
const advance = face.advanceWidth(glyphId); // Includes HVAR delta

AvarTable ​

Axis variations for non-linear axis mappings.

Maps user coordinates to normalized coordinates for each axis.

MvarTable ​

Metrics variations for font-wide metrics.

Supported Metrics:

  • Ascender, Descender
  • Line gap
  • Cap height, x-height
  • Subscript/superscript metrics

Vertical Layout Tables ​

VheaTable ​

Vertical header (vertical writing systems).

Key Fields:

  • ascender: number - Vertical ascender
  • descender: number - Vertical descender
  • lineGap: number - Vertical line gap
  • numberOfVMetrics: number - Number of vMetric entries

VmtxTable ​

Vertical metrics for each glyph.

VorgTable ​

Vertical origin for CJK fonts.

Color Font Tables ​

ColrTable ​

Color layered glyphs (COLRv0 and COLRv1).

Features:

  • Simple color layers (v0)
  • Gradient fills (v1)
  • Transformations (v1)
  • Compositing modes (v1)

Access:

typescript
import { hasColorGlyph, getColorLayers } from "typeshaper";

if (hasColorGlyph(font.colr, glyphId)) {
  const layers = getColorLayers(font.colr, glyphId);
}

CpalTable ​

Color palettes for COLR table.

Access:

typescript
import { getColor } from "typeshaper";

const color = getColor(font.cpal, paletteIndex, colorIndex);
// Returns { red, green, blue, alpha }

SvgTable ​

SVG glyphs embedded in font.

Access:

typescript
import { hasSvgGlyph, getSvgDocument } from "typeshaper";

if (hasSvgGlyph(font.svg, glyphId)) {
  const svg = getSvgDocument(font.svg, glyphId);
}

SbixTable ​

Apple bitmap glyphs with alpha channel.

Features:

  • PNG, JPEG, TIFF formats
  • Multiple PPEM sizes
  • Dupe glyph handling

Access:

typescript
import { hasGlyphBitmap, getSbixGlyphBitmap } from "typeshaper";

const bitmap = getSbixGlyphBitmap(font.sbix, glyphId, ppem);

CBDT/CBLC Tables ​

Google color bitmap format.

Features:

  • Multiple bitmap formats
  • Embedded bitmaps at various sizes

AAT Tables ​

MorxTable ​

Extended morphing (Apple Advanced Typography).

Subtable Types:

  • Rearrangement - Reorder glyphs
  • Contextual - Context-dependent substitution
  • Ligature - Ligature formation
  • Non-contextual - Simple substitution
  • Insertion - Insert glyphs

Usage:

typescript
// Automatically applied if GSUB not present
const shaped = shape(font, buffer);

KerxTable ​

Extended kerning (AAT).

Features:

  • Format 0: Ordered list of kerning pairs
  • Format 1: State table kerning
  • Format 2: Simple kern array
  • Format 4: Control point kerning
  • Format 6: Simple index kerning

TrakTable ​

Tracking (letter spacing) adjustments.

Access:

typescript
import { applyTracking } from "typeshaper";

const adjustment = applyTracking(font.trak, pointSize, tracking);

FeatTable ​

Feature names for AAT features.

Usage:

typescript
import { getAllFeatures, getFeature } from "typeshaper";

const features = getAllFeatures(font.feat);

Outline Tables ​

LocaTable ​

Glyph location table for TrueType outlines.

Maps glyph IDs to offsets in the glyf table.

GlyfTable ​

Glyph data for TrueType outlines.

Glyph Types:

  • Simple - Single contour
  • Composite - Multiple component glyphs

Access:

typescript
const contours = font.getGlyphContours(glyphId);
const bounds = font.getGlyphBounds(glyphId);

CFF / CFF2 Tables ​

Compact Font Format (PostScript outlines).

  • CFF - Static fonts
  • CFF2 - Variable fonts

Access:

typescript
const contours = font.getGlyphContours(glyphId); // Works for both CFF and TrueType

Hinting Tables ​

FpgmTable ​

Font program executed once per font.

PrepTable ​

Control value program executed once per size.

CvtTable ​

Control value table with values used by instructions.

GaspTable ​

Grid-fitting and scan-conversion procedure.

Defines which size ranges use hinting vs. smoothing.

Other Tables ​

Os2Table ​

OS/2 and Windows metrics.

Key Fields:

  • Weight class
  • Width class
  • Type flags
  • Strikeout/underline metrics
  • Unicode ranges
  • Code page ranges

NameTable ​

Naming table with human-readable strings.

Name IDs:

  • 0: Copyright
  • 1: Font family
  • 2: Subfamily
  • 4: Full name
  • 6: PostScript name
  • 16: Typographic family
  • 17: Typographic subfamily

PostTable ​

PostScript information.

Features:

  • Glyph names
  • Italic angle
  • Underline metrics
  • Fixed pitch flag

StatTable ​

Style attributes for variable fonts.

Features:

  • Axis records
  • Axis values
  • Elidable axis value names

Usage:

typescript
import { getAxisRecord, matchAxisValue } from "typeshaper";

const axis = getAxisRecord(font.stat, 0);

Table Access Pattern ​

All tables use lazy loading:

typescript
// Table is parsed on first access
const gdef = font.gdef; // Parses GDEF table

// Subsequent accesses use cached value
const gdef2 = font.gdef; // Returns cached table

// Check for table presence
if (font.hasTable(Tags.GSUB)) {
  const gsub = font.gsub;
}