otlLib: Routines for working with OpenType Layout

The fontTools.otlLib library provides routines to help you create the subtables and other data structures you need when you are editing a font’s GSUB and GPOS tables: substitution and positioning rules, anchors, lookups, coverage tables and so on.

High-level OpenType Layout Lookup Builders

class fontTools.otlLib.builder.AlternateSubstBuilder(font, location)[source]

Builds an Alternate Substitution (GSUB3) lookup.

Users are expected to manually add alternate glyph substitutions to the alternates attribute after the object has been initialized, e.g.:

builder.alternates["A"] = ["A.alt1", "A.alt2"]
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

alternates

An ordered dictionary of alternates, mapping glyph names to a list of names of alternates.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the alternate substitution lookup.

getAlternateGlyphs()[source]

Helper for building ‘aalt’ features.

add_subtable_break(location)[source]

Add an explicit subtable break.

Parameters

location – A string or tuple representing the location in the original source which produced this break, or None if no location is provided.

class fontTools.otlLib.builder.ChainContextPosBuilder(font, location)[source]

Builds a Chained Contextual Positioning (GPOS8) lookup.

Users are expected to manually add rules to the rules attribute after the object has been initialized, e.g.:

# pos [A B] [C D] x' lookup lu1 y' z' lookup lu2 E;

prefix  = [ ["A", "B"], ["C", "D"] ]
suffix  = [ ["E"] ]
glyphs  = [ ["x"], ["y"], ["z"] ]
lookups = [ [lu1], None,  [lu2] ]
builder.rules.append( (prefix, glyphs, suffix, lookups) )
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

rules

A list of tuples representing the rules in this lookup.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

find_chainable_single_pos(lookups, glyphs, value)[source]

Helper for add_single_pos_chained_()

class fontTools.otlLib.builder.ChainContextSubstBuilder(font, location)[source]

Builds a Chained Contextual Substitution (GSUB6) lookup.

Users are expected to manually add rules to the rules attribute after the object has been initialized, e.g.:

# sub [A B] [C D] x' lookup lu1 y' z' lookup lu2 E;

prefix  = [ ["A", "B"], ["C", "D"] ]
suffix  = [ ["E"] ]
glyphs  = [ ["x"], ["y"], ["z"] ]
lookups = [ [lu1], None,  [lu2] ]
builder.rules.append( (prefix, glyphs, suffix, lookups) )
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

rules

A list of tuples representing the rules in this lookup.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

getAlternateGlyphs()[source]

Helper for building ‘aalt’ features.

find_chainable_single_subst(glyphs)[source]

Helper for add_single_subst_chained_()

class fontTools.otlLib.builder.LigatureSubstBuilder(font, location)[source]

Builds a Ligature Substitution (GSUB4) lookup.

Users are expected to manually add ligatures to the ligatures attribute after the object has been initialized, e.g.:

# sub f i by f_i;
builder.ligatures[("f","f","i")] = "f_f_i"
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

ligatures

An ordered dictionary mapping a tuple of glyph names to the ligature glyphname.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the ligature substitution lookup.

add_subtable_break(location)[source]

Add an explicit subtable break.

Parameters

location – A string or tuple representing the location in the original source which produced this break, or None if no location is provided.

class fontTools.otlLib.builder.MultipleSubstBuilder(font, location)[source]

Builds a Multiple Substitution (GSUB2) lookup.

Users are expected to manually add substitutions to the mapping attribute after the object has been initialized, e.g.:

# sub uni06C0 by uni06D5.fina hamza.above;
builder.mapping["uni06C0"] = [ "uni06D5.fina", "hamza.above"]
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

mapping

An ordered dictionary mapping a glyph name to a list of substituted glyph names.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

add_subtable_break(location)[source]

Add an explicit subtable break.

Parameters

location – A string or tuple representing the location in the original source which produced this break, or None if no location is provided.

class fontTools.otlLib.builder.CursivePosBuilder(font, location)[source]

Builds a Cursive Positioning (GPOS3) lookup.

font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

attachments

An ordered dictionary mapping a glyph name to a two-element tuple of otTables.Anchor objects.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

add_attachment(location, glyphs, entryAnchor, exitAnchor)[source]

Adds attachment information to the cursive positioning lookup.

Parameters
  • location – A string or tuple representing the location in the original source which produced this lookup. (Unused.)

  • glyphs – A list of glyph names sharing these entry and exit anchor locations.

  • entryAnchor – A otTables.Anchor object representing the entry anchor, or None if no entry anchor is present.

  • exitAnchor – A otTables.Anchor object representing the exit anchor, or None if no exit anchor is present.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the cursive positioning lookup.

class fontTools.otlLib.builder.MarkBasePosBuilder(font, location)[source]

Builds a Mark-To-Base Positioning (GPOS4) lookup.

Users are expected to manually add marks and bases to the marks and bases attributes after the object has been initialized, e.g.:

builder.marks["acute"]   = (0, a1)
builder.marks["grave"]   = (0, a1)
builder.marks["cedilla"] = (1, a2)
builder.bases["a"] = {0: a3, 1: a5}
builder.bases["b"] = {0: a4, 1: a5}
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

marks

An dictionary mapping a glyph name to a two-element tuple containing a mark class ID and otTables.Anchor object.

bases

An dictionary mapping a glyph name to a dictionary of mark class IDs and otTables.Anchor object.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

inferGlyphClasses()[source]

Infers glyph glasses for the GDEF table, such as {“cedilla”:3}.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the mark-to-base positioning lookup.

class fontTools.otlLib.builder.MarkLigPosBuilder(font, location)[source]

Builds a Mark-To-Ligature Positioning (GPOS5) lookup.

Users are expected to manually add marks and bases to the marks and ligatures attributes after the object has been initialized, e.g.:

builder.marks["acute"]   = (0, a1)
builder.marks["grave"]   = (0, a1)
builder.marks["cedilla"] = (1, a2)
builder.ligatures["f_i"] = [
    { 0: a3, 1: a5 }, # f
    { 0: a4, 1: a5 }  # i
]
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

marks

An dictionary mapping a glyph name to a two-element tuple containing a mark class ID and otTables.Anchor object.

ligatures

An dictionary mapping a glyph name to an array with one element for each ligature component. Each array element should be a dictionary mapping mark class IDs to otTables.Anchor objects.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

inferGlyphClasses()[source]

Infers glyph glasses for the GDEF table, such as {“cedilla”:3}.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the mark-to-ligature positioning lookup.

class fontTools.otlLib.builder.MarkMarkPosBuilder(font, location)[source]

Builds a Mark-To-Mark Positioning (GPOS6) lookup.

Users are expected to manually add marks and bases to the marks and baseMarks attributes after the object has been initialized, e.g.:

builder.marks["acute"]     = (0, a1)
builder.marks["grave"]     = (0, a1)
builder.marks["cedilla"]   = (1, a2)
builder.baseMarks["acute"] = (0, a3)
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

marks

An dictionary mapping a glyph name to a two-element tuple containing a mark class ID and otTables.Anchor object.

baseMarks

An dictionary mapping a glyph name to a two-element tuple containing a mark class ID and otTables.Anchor object.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

inferGlyphClasses()[source]

Infers glyph glasses for the GDEF table, such as {“cedilla”:3}.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the mark-to-mark positioning lookup.

class fontTools.otlLib.builder.ReverseChainSingleSubstBuilder(font, location)[source]

Builds a Reverse Chaining Contextual Single Substitution (GSUB8) lookup.

Users are expected to manually add substitutions to the substitutions attribute after the object has been initialized, e.g.:

# reversesub [a e n] d' by d.alt;
prefix = [ ["a", "e", "n"] ]
suffix = []
mapping = { "d": "d.alt" }
builder.substitutions.append( (prefix, suffix, mapping) )
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

substitutions

A three-element tuple consisting of a prefix sequence, a suffix sequence, and a dictionary of single substitutions.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the chained contextual substitution lookup.

add_subtable_break(location)[source]

Add an explicit subtable break.

Parameters

location – A string or tuple representing the location in the original source which produced this break, or None if no location is provided.

class fontTools.otlLib.builder.SingleSubstBuilder(font, location)[source]

Builds a Single Substitution (GSUB1) lookup.

Users are expected to manually add substitutions to the mapping attribute after the object has been initialized, e.g.:

# sub x by y;
builder.mapping["x"] = "y"
font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

mapping

A dictionary mapping a single glyph name to another glyph name.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the multiple substitution lookup.

getAlternateGlyphs()[source]

Helper for building ‘aalt’ features.

add_subtable_break(location)[source]

Add an explicit subtable break.

Parameters

location – A string or tuple representing the location in the original source which produced this break, or None if no location is provided.

class fontTools.otlLib.builder.ClassPairPosSubtableBuilder(builder)[source]

Builds class-based Pair Positioning (GPOS2 format 2) subtables.

Note that this does not build a GPOS2 otTables.Lookup directly, but builds a list of otTables.PairPos subtables. It is used by the PairPosBuilder below.

builder

A pair positioning lookup builder.

Type

PairPosBuilder

addPair(gc1, value1, gc2, value2)[source]

Add a pair positioning rule.

Parameters
  • gc1 – A set of glyph names for the “left” glyph

  • value1 – An otTables.ValueRecord object for the left glyph’s positioning.

  • gc2 – A set of glyph names for the “right” glyph

  • value2 – An otTables.ValueRecord object for the right glyph’s positioning.

addSubtableBreak()[source]

Add an explicit subtable break at this point.

subtables()[source]

Return the list of otTables.PairPos subtables constructed.

class fontTools.otlLib.builder.PairPosBuilder(font, location)[source]

Builds a Pair Positioning (GPOS2) lookup.

font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

pairs

An array of class-based pair positioning tuples. Usually manipulated with the addClassPair() method below.

glyphPairs

A dictionary mapping a tuple of glyph names to a tuple of otTables.ValueRecord objects. Usually manipulated with the addGlyphPair() method below.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

addClassPair(location, glyphclass1, value1, glyphclass2, value2)[source]

Add a class pair positioning rule to the current lookup.

Parameters
  • location – A string or tuple representing the location in the original source which produced this rule. Unused.

  • glyphclass1 – A set of glyph names for the “left” glyph in the pair.

  • value1 – A otTables.ValueRecord for positioning the left glyph.

  • glyphclass2 – A set of glyph names for the “right” glyph in the pair.

  • value2 – A otTables.ValueRecord for positioning the right glyph.

addGlyphPair(location, glyph1, value1, glyph2, value2)[source]

Add a glyph pair positioning rule to the current lookup.

Parameters
  • location – A string or tuple representing the location in the original source which produced this rule.

  • glyph1 – A glyph name for the “left” glyph in the pair.

  • value1 – A otTables.ValueRecord for positioning the left glyph.

  • glyph2 – A glyph name for the “right” glyph in the pair.

  • value2 – A otTables.ValueRecord for positioning the right glyph.

add_subtable_break(location)[source]

Add an explicit subtable break.

Parameters

location – A string or tuple representing the location in the original source which produced this break, or None if no location is provided.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the pair positioning lookup.

class fontTools.otlLib.builder.SinglePosBuilder(font, location)[source]

Builds a Single Positioning (GPOS1) lookup.

font

A font object.

Type

fontTools.TTLib.TTFont

location

A string or tuple representing the location in the original source which produced this lookup.

mapping

A dictionary mapping a glyph name to a otTables.ValueRecord objects. Usually manipulated with the add_pos() method below.

lookupflag

The lookup’s flag

Type

int

markFilterSet

Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

add_pos(location, glyph, otValueRecord)[source]

Add a single positioning rule.

Parameters
  • location – A string or tuple representing the location in the original source which produced this lookup.

  • glyph – A glyph name.

  • otValueRection – A otTables.ValueRecord used to position the glyph.

build()[source]

Build the lookup.

Returns

An otTables.Lookup object representing the single positioning lookup.

Common OpenType Layout Data Structures

fontTools.otlLib.builder.buildCoverage(glyphs, glyphMap)[source]

Builds a coverage table.

Coverage tables (as defined in the OpenType spec) are used in all OpenType Layout lookups apart from the Extension type, and define the glyphs involved in a layout subtable. This allows shaping engines to compare the glyph stream with the coverage table and quickly determine whether a subtable should be involved in a shaping operation.

This function takes a list of glyphs and a glyphname-to-ID map, and returns a Coverage object representing the coverage table.

Example:

glyphMap = font.getReverseGlyphMap()
glyphs = [ "A", "B", "C" ]
coverage = buildCoverage(glyphs, glyphMap)
Parameters
  • glyphs – a sequence of glyph names.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

An otTables.Coverage object or None if there are no glyphs supplied.

fontTools.otlLib.builder.buildLookup(subtables, flags=0, markFilterSet=None)[source]

Turns a collection of rules into a lookup.

A Lookup (as defined in the OpenType Spec) wraps the individual rules in a layout operation (substitution or positioning) in a data structure expressing their overall lookup type - for example, single substitution, mark-to-base attachment, and so on - as well as the lookup flags and any mark filtering sets. You may import the following constants to express lookup flags:

  • LOOKUP_FLAG_RIGHT_TO_LEFT

  • LOOKUP_FLAG_IGNORE_BASE_GLYPHS

  • LOOKUP_FLAG_IGNORE_LIGATURES

  • LOOKUP_FLAG_IGNORE_MARKS

  • LOOKUP_FLAG_USE_MARK_FILTERING_SET

Parameters
  • subtables – A list of layout subtable objects (e.g. MultipleSubst, PairPos, etc.) or None.

  • flags (int) – This lookup’s flags.

  • markFilterSet – Either None if no mark filtering set is used, or an integer representing the filtering set to be used for this lookup. If a mark filtering set is provided, LOOKUP_FLAG_USE_MARK_FILTERING_SET will be set on the lookup’s flags.

Returns

An otTables.Lookup object or None if there are no subtables supplied.

Low-level GSUB Table Lookup Builders

These functions deal with the “simple” lookup types. See above for classes to help build more complex lookups (contextual and chaining lookups).

fontTools.otlLib.builder.buildAlternateSubstSubtable(mapping)[source]

Builds an alternate substitution (GSUB3) subtable.

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.AlternateSubstBuilder instead.

Parameters

mapping – A dictionary mapping input glyph names to a list of output glyph names.

Returns

An otTables.AlternateSubst object or None if the mapping dictionary is empty.

fontTools.otlLib.builder.buildLigatureSubstSubtable(mapping)[source]

Builds a ligature substitution (GSUB4) subtable.

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.LigatureSubstBuilder instead.

Example:

# sub f f i by f_f_i;
# sub f i by f_i;

subtable = buildLigatureSubstSubtable({
    ("f", "f", "i"): "f_f_i",
    ("f", "i"): "f_i",
})
Parameters

mapping – A dictionary mapping tuples of glyph names to output glyph names.

Returns

An otTables.LigatureSubst object or None if the mapping dictionary is empty.

fontTools.otlLib.builder.buildMultipleSubstSubtable(mapping)[source]

Builds a multiple substitution (GSUB2) subtable.

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.MultipleSubstBuilder instead.

Example:

# sub uni06C0 by uni06D5.fina hamza.above
# sub uni06C2 by uni06C1.fina hamza.above;

subtable = buildMultipleSubstSubtable({
    "uni06C0": [ "uni06D5.fina", "hamza.above"],
    "uni06C2": [ "uni06D1.fina", "hamza.above"]
})
Parameters

mapping – A dictionary mapping input glyph names to a list of output glyph names.

Returns

An otTables.MultipleSubst object or None if the mapping dictionary is empty.

fontTools.otlLib.builder.buildSingleSubstSubtable(mapping)[source]

Builds a single substitution (GSUB1) subtable.

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.SingleSubstBuilder instead.

Parameters

mapping – A dictionary mapping input glyph names to output glyph names.

Returns

An otTables.SingleSubst object, or None if the mapping dictionary is empty.

GPOS Shared Table Builders

The functions help build the GPOS shared tables as defined in the OpenType spec: value records, anchors, mark arrays and mark record tables.

fontTools.otlLib.builder.buildAnchor(x, y, point=None, deviceX=None, deviceY=None)[source]

Builds an Anchor table.

This determines the appropriate anchor format based on the passed parameters.

Parameters
  • x (int) – X coordinate.

  • y (int) – Y coordinate.

  • point (int) – Index of glyph contour point, if provided.

  • deviceX (otTables.Device) – X coordinate device table, if provided.

  • deviceY (otTables.Device) – Y coordinate device table, if provided.

Returns

An otTables.Anchor object.

fontTools.otlLib.builder.buildBaseArray(bases, numMarkClasses, glyphMap)[source]

Builds a base array record.

As part of building mark-to-base positioning rules, you will need to define a BaseArray record, which “defines for each base glyph an array of anchors, one for each mark class.” This function builds the base array subtable.

Example:

bases = {"a": {0: a3, 1: a5}, "b": {0: a4, 1: a5}}
basearray = buildBaseArray(bases, 2, font.getReverseGlyphMap())
Parameters
  • bases (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being dictionaries mapping mark class ID to the appropriate otTables.Anchor object used for attaching marks of that class.

  • numMarkClasses (int) – The total number of mark classes for which anchors are defined.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

An otTables.BaseArray object.

fontTools.otlLib.builder.buildComponentRecord(anchors)[source]

Builds a component record.

As part of building mark-to-ligature positioning rules, you will need to define ComponentRecord objects, which contain “an array of offsets… to the Anchor tables that define all the attachment points used to attach marks to the component.” This function builds the component record.

Parameters

anchors – A list of otTables.Anchor objects or None.

Returns

A otTables.ComponentRecord object or None if no anchors are supplied.

fontTools.otlLib.builder.buildDevice(deltas)[source]

Builds a Device record as part of a ValueRecord or Anchor.

Device tables specify size-specific adjustments to value records and anchors to reflect changes based on the resolution of the output. For example, one could specify that an anchor’s Y position should be increased by 1 pixel when displayed at 8 pixels per em. This routine builds device records.

Parameters

deltas – A dictionary mapping pixels-per-em sizes to the delta adjustment in pixels when the font is displayed at that size.

Returns

An otTables.Device object if any deltas were supplied, or None otherwise.

fontTools.otlLib.builder.buildMarkArray(marks, glyphMap)[source]

Builds a mark array subtable.

As part of building mark-to-* positioning rules, you will need to define a MarkArray subtable, which “defines the class and the anchor point for a mark glyph.” This function builds the mark array subtable.

Example:

mark = {
    "acute": (0, buildAnchor(300,712)),
    # ...
}
markarray = buildMarkArray(marks, font.getReverseGlyphMap())
Parameters
  • marks (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being a tuple of mark class number and an otTables.Anchor object representing the mark’s attachment point.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

An otTables.MarkArray object.

fontTools.otlLib.builder.buildMarkArray(marks, glyphMap)[source]

Builds a mark array subtable.

As part of building mark-to-* positioning rules, you will need to define a MarkArray subtable, which “defines the class and the anchor point for a mark glyph.” This function builds the mark array subtable.

Example:

mark = {
    "acute": (0, buildAnchor(300,712)),
    # ...
}
markarray = buildMarkArray(marks, font.getReverseGlyphMap())
Parameters
  • marks (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being a tuple of mark class number and an otTables.Anchor object representing the mark’s attachment point.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

An otTables.MarkArray object.

fontTools.otlLib.builder.buildValue(value)[source]

Builds a positioning value record.

Value records are used to specify coordinates and adjustments for positioning and attaching glyphs. Many of the positioning functions in this library take otTables.ValueRecord objects as arguments. This function builds value records from dictionaries.

Parameters

value (dict) – A dictionary with zero or more of the following keys: - xPlacement - yPlacement - xAdvance - yAdvance - xPlaDevice - yPlaDevice - xAdvDevice - yAdvDevice

Returns

An otTables.ValueRecord object.

fontTools.otlLib.builder.buildValue(value)[source]

Builds a positioning value record.

Value records are used to specify coordinates and adjustments for positioning and attaching glyphs. Many of the positioning functions in this library take otTables.ValueRecord objects as arguments. This function builds value records from dictionaries.

Parameters

value (dict) – A dictionary with zero or more of the following keys: - xPlacement - yPlacement - xAdvance - yAdvance - xPlaDevice - yPlaDevice - xAdvDevice - yAdvDevice

Returns

An otTables.ValueRecord object.

Low-level GPOS Table Lookup Builders

These functions deal with the “simple” lookup types. See above for classes to help build more complex lookups (contextual and chaining lookups).

fontTools.otlLib.builder.buildCursivePosSubtable(attach, glyphMap)[source]

Builds a cursive positioning (GPOS3) subtable.

Cursive positioning lookups are made up of a coverage table of glyphs, and a set of EntryExitRecord records containing the anchors for each glyph. This function builds the cursive positioning subtable.

Example:

subtable = buildCursivePosSubtable({
    "AlifIni": (None, buildAnchor(0, 50)),
    "BehMed": (buildAnchor(500,250), buildAnchor(0,50)),
    # ...
}, font.getReverseGlyphMap())
Parameters
  • attach (dict) – A mapping between glyph names and a tuple of two otTables.Anchor objects representing entry and exit anchors.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

An otTables.CursivePos object, or None if the attachment dictionary was empty.

fontTools.otlLib.builder.buildLigatureArray(ligs, numMarkClasses, glyphMap)[source]

Builds a LigatureArray subtable.

As part of building a mark-to-ligature lookup, you will need to define the set of anchors (for each mark class) on each component of the ligature where marks can be attached. For example, for an Arabic divine name ligature (lam lam heh), you may want to specify mark attachment positioning for superior marks (fatha, etc.) and inferior marks (kasra, etc.) on each glyph of the ligature. This routine builds the ligature array record.

Example:

buildLigatureArray({
    "lam-lam-heh": [
        { 0: superiorAnchor1, 1: inferiorAnchor1 }, # attach points for lam1
        { 0: superiorAnchor2, 1: inferiorAnchor2 }, # attach points for lam2
        { 0: superiorAnchor3, 1: inferiorAnchor3 }, # attach points for heh
    ]
}, 2, font.getReverseGlyphMap())
Parameters
  • ligs (dict) – A mapping of ligature names to an array of dictionaries: for each component glyph in the ligature, an dictionary mapping mark class IDs to anchors.

  • numMarkClasses (int) – The number of mark classes.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

An otTables.LigatureArray object if deltas were supplied.

fontTools.otlLib.builder.buildMarkBasePos(marks, bases, glyphMap)[source]

Build a list of MarkBasePos (GPOS4) subtables.

This routine turns a set of marks and bases into a list of mark-to-base positioning subtables. Currently the list will contain a single subtable containing all marks and bases, although at a later date it may return the optimal list of subtables subsetting the marks and bases into groups which save space. See buildMarkBasePosSubtable() below.

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.MarkBasePosBuilder instead.

Example:

# a1, a2, a3, a4, a5 = buildAnchor(500, 100), ...

marks = {"acute": (0, a1), "grave": (0, a1), "cedilla": (1, a2)}
bases = {"a": {0: a3, 1: a5}, "b": {0: a4, 1: a5}}
markbaseposes = buildMarkBasePos(marks, bases, font.getReverseGlyphMap())
Parameters
  • marks (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being a tuple of mark class number and an otTables.Anchor object representing the mark’s attachment point. (See buildMarkArray().)

  • bases (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being dictionaries mapping mark class ID to the appropriate otTables.Anchor object used for attaching marks of that class. (See buildBaseArray().)

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

A list of otTables.MarkBasePos objects.

fontTools.otlLib.builder.buildMarkBasePosSubtable(marks, bases, glyphMap)[source]

Build a single MarkBasePos (GPOS4) subtable.

This builds a mark-to-base lookup subtable containing all of the referenced marks and bases. See buildMarkBasePos().

Parameters
  • marks (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being a tuple of mark class number and an otTables.Anchor object representing the mark’s attachment point. (See buildMarkArray().)

  • bases (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being dictionaries mapping mark class ID to the appropriate otTables.Anchor object used for attaching marks of that class. (See buildBaseArray().)

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

A otTables.MarkBasePos object.

fontTools.otlLib.builder.buildMarkLigPos(marks, ligs, glyphMap)[source]

Build a list of MarkLigPos (GPOS5) subtables.

This routine turns a set of marks and ligatures into a list of mark-to-ligature positioning subtables. Currently the list will contain a single subtable containing all marks and ligatures, although at a later date it may return the optimal list of subtables subsetting the marks and ligatures into groups which save space. See buildMarkLigPosSubtable() below.

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.MarkLigPosBuilder instead.

Example:

# a1, a2, a3, a4, a5 = buildAnchor(500, 100), ...
marks = {
    "acute": (0, a1),
    "grave": (0, a1),
    "cedilla": (1, a2)
}
ligs = {
    "f_i": [
        { 0: a3, 1: a5 }, # f
        { 0: a4, 1: a5 }  # i
        ],
#   "c_t": [{...}, {...}]
}
markligposes = buildMarkLigPos(marks, ligs,
    font.getReverseGlyphMap())
Parameters
  • marks (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being a tuple of mark class number and an otTables.Anchor object representing the mark’s attachment point. (See buildMarkArray().)

  • ligs (dict) – A mapping of ligature names to an array of dictionaries: for each component glyph in the ligature, an dictionary mapping mark class IDs to anchors. (See buildLigatureArray().)

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

A list of otTables.MarkLigPos objects.

fontTools.otlLib.builder.buildMarkLigPosSubtable(marks, ligs, glyphMap)[source]

Build a single MarkLigPos (GPOS5) subtable.

This builds a mark-to-base lookup subtable containing all of the referenced marks and bases. See buildMarkLigPos().

Parameters
  • marks (dict) – A dictionary mapping anchors to glyphs; the keys being glyph names, and the values being a tuple of mark class number and an otTables.Anchor object representing the mark’s attachment point. (See buildMarkArray().)

  • ligs (dict) – A mapping of ligature names to an array of dictionaries: for each component glyph in the ligature, an dictionary mapping mark class IDs to anchors. (See buildLigatureArray().)

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

A otTables.MarkLigPos object.

fontTools.otlLib.builder.buildPairPosClassesSubtable(pairs, glyphMap, valueFormat1=None, valueFormat2=None)[source]

Builds a class pair adjustment (GPOS2 format 2) subtable.

Kerning tables are generally expressed as pair positioning tables using class-based pair adjustments. This routine builds format 2 PairPos subtables.

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.ClassPairPosSubtableBuilder instead, as this takes care of ensuring that the supplied pairs can be formed into non-overlapping classes and emitting individual subtables whenever the non-overlapping requirement means that a new subtable is required.

Example:

pairs = {}

pairs[(
    [ "K", "X" ],
    [ "W", "V" ]
)] = ( buildValue(xAdvance=+5), buildValue() )
# pairs[(... , ...)] = (..., ...)

pairpos = buildPairPosClassesSubtable(pairs, font.getReverseGlyphMap())
Parameters
  • pairs (dict) – Pair positioning data; the keys being a two-element tuple of lists of glyphnames, and the values being a two-element tuple of otTables.ValueRecord objects.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

  • valueFormat1 – Force the “left” value records to the given format.

  • valueFormat2 – Force the “right” value records to the given format.

Returns

A otTables.PairPos object.

fontTools.otlLib.builder.buildPairPosGlyphs(pairs, glyphMap)[source]

Builds a list of glyph-based pair adjustment (GPOS2 format 1) subtables.

This organises a list of pair positioning adjustments into subtables based on common value record formats.

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.PairPosBuilder instead.

Example:

pairs = {
    ("K", "W"): ( buildValue(xAdvance=+5), buildValue() ),
    ("K", "V"): ( buildValue(xAdvance=+5), buildValue() ),
    # ...
}

subtables = buildPairPosGlyphs(pairs, font.getReverseGlyphMap())
Parameters
  • pairs (dict) – Pair positioning data; the keys being a two-element tuple of glyphnames, and the values being a two-element tuple of otTables.ValueRecord objects.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

A list of otTables.PairPos objects.

fontTools.otlLib.builder.buildPairPosGlyphsSubtable(pairs, glyphMap, valueFormat1=None, valueFormat2=None)[source]

Builds a single glyph-based pair adjustment (GPOS2 format 1) subtable.

This builds a PairPos subtable from a dictionary of glyph pairs and their positioning adjustments. See also buildPairPosGlyphs().

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.PairPosBuilder instead.

Example:

pairs = {
    ("K", "W"): ( buildValue(xAdvance=+5), buildValue() ),
    ("K", "V"): ( buildValue(xAdvance=+5), buildValue() ),
    # ...
}

pairpos = buildPairPosGlyphsSubtable(pairs, font.getReverseGlyphMap())
Parameters
  • pairs (dict) – Pair positioning data; the keys being a two-element tuple of glyphnames, and the values being a two-element tuple of otTables.ValueRecord objects.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

  • valueFormat1 – Force the “left” value records to the given format.

  • valueFormat2 – Force the “right” value records to the given format.

Returns

A otTables.PairPos object.

fontTools.otlLib.builder.buildSinglePos(mapping, glyphMap)[source]

Builds a list of single adjustment (GPOS1) subtables.

This builds a list of SinglePos subtables from a dictionary of glyph names and their positioning adjustments. The format of the subtables are determined to optimize the size of the resulting subtables. See also buildSinglePosSubtable().

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.SinglePosBuilder instead.

Example:

mapping = {
    "V": buildValue({ "xAdvance" : +5 }),
    # ...
}

subtables = buildSinglePos(pairs, font.getReverseGlyphMap())
Parameters
  • mapping (dict) – A mapping between glyphnames and otTables.ValueRecord objects.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

A list of otTables.SinglePos objects.

fontTools.otlLib.builder.buildSinglePosSubtable(values, glyphMap)[source]

Builds a single adjustment (GPOS1) subtable.

This builds a list of SinglePos subtables from a dictionary of glyph names and their positioning adjustments. The format of the subtable is determined to optimize the size of the output. See also buildSinglePos().

Note that if you are implementing a layout compiler, you may find it more flexible to use fontTools.otlLib.lookupBuilders.SinglePosBuilder instead.

Example:

mapping = {
    "V": buildValue({ "xAdvance" : +5 }),
    # ...
}

subtable = buildSinglePos(pairs, font.getReverseGlyphMap())
Parameters
  • mapping (dict) – A mapping between glyphnames and otTables.ValueRecord objects.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

A otTables.SinglePos object.

GDEF Table Subtable Builders

These functions build subtables for elements of the GDEF table.

fontTools.otlLib.builder.buildAttachList(attachPoints, glyphMap)[source]

Builds an AttachList subtable.

A GDEF table may contain an Attachment Point List table (AttachList) which stores the contour indices of attachment points for glyphs with attachment points. This routine builds AttachList subtables.

Parameters

attachPoints (dict) – A mapping between glyph names and a list of contour indices.

Returns

An otTables.AttachList object if attachment points are supplied,

or None otherwise.

fontTools.otlLib.builder.buildLigCaretList(coords, points, glyphMap)[source]

Builds a ligature caret list table.

Ligatures appear as a single glyph representing multiple characters; however when, for example, editing text containing a f_i ligature, the user may want to place the cursor between the f and the i. The ligature caret list in the GDEF table specifies the position to display the “caret” (the character insertion indicator, typically a flashing vertical bar) “inside” the ligature to represent an insertion point. The insertion positions may be specified either by coordinate or by contour point.

Example:

coords = {
    "f_f_i": [300, 600] # f|fi cursor at 300 units, ff|i cursor at 600.
}
points = {
    "c_t": [28] # c|t cursor appears at coordinate of contour point 28.
}
ligcaretlist = buildLigCaretList(coords, points, font.getReverseGlyphMap())
Parameters
  • coords – A mapping between glyph names and a list of coordinates for the insertion point of each ligature component after the first one.

  • points – A mapping between glyph names and a list of contour points for the insertion point of each ligature component after the first one.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

A otTables.LigCaretList object if any carets are present, or

None otherwise.

fontTools.otlLib.builder.buildMarkGlyphSetsDef(markSets, glyphMap)[source]

Builds a mark glyph sets definition table.

OpenType Layout lookups may choose to use mark filtering sets to consider or ignore particular combinations of marks. These sets are specified by setting a flag on the lookup, but the mark filtering sets are defined in the GDEF table. This routine builds the subtable containing the mark glyph set definitions.

Example:

set0 = set("acute", "grave")
set1 = set("caron", "grave")

markglyphsets = buildMarkGlyphSetsDef([set0, set1], font.getReverseGlyphMap())
Parameters
  • markSets – A list of sets of glyphnames.

  • glyphMap – a glyph name to ID map, typically returned from font.getReverseGlyphMap().

Returns

An otTables.MarkGlyphSetsDef object.

STAT Table Builder

fontTools.otlLib.builder.buildStatTable(ttFont, axes, locations=None, elidedFallbackName=2)[source]

Add a ‘STAT’ table to ‘ttFont’.

‘axes’ is a list of dictionaries describing axes and their values.

Example:

axes = [
    dict(
        tag="wght",
        name="Weight",
        ordering=0,  # optional
        values=[
            dict(value=100, name='Thin'),
            dict(value=300, name='Light'),
            dict(value=400, name='Regular', flags=0x2),
            dict(value=900, name='Black'),
        ],
    )
]

Each axis dict must have ‘tag’ and ‘name’ items. ‘tag’ maps to the ‘AxisTag’ field. ‘name’ can be a name ID (int), a string, or a dictionary containing multilingual names (see the addMultilingualName() name table method), and will translate to the AxisNameID field.

An axis dict may contain an ‘ordering’ item that maps to the AxisOrdering field. If omitted, the order of the axes list is used to calculate AxisOrdering fields.

The axis dict may contain a ‘values’ item, which is a list of dictionaries describing AxisValue records belonging to this axis.

Each value dict must have a ‘name’ item, which can be a name ID (int), a string, or a dictionary containing multilingual names, like the axis name. It translates to the ValueNameID field.

Optionally the value dict can contain a ‘flags’ item. It maps to the AxisValue Flags field, and will be 0 when omitted.

The format of the AxisValue is determined by the remaining contents of the value dictionary:

If the value dict contains a ‘value’ item, an AxisValue record Format 1 is created. If in addition to the ‘value’ item it contains a ‘linkedValue’ item, an AxisValue record Format 3 is built.

If the value dict contains a ‘nominalValue’ item, an AxisValue record Format 2 is built. Optionally it may contain ‘rangeMinValue’ and ‘rangeMaxValue’ items. These map to -Infinity and +Infinity respectively if omitted.

You cannot specify Format 4 AxisValue tables this way, as they are not tied to a single axis, and specify a name for a location that is defined by multiple axes values. Instead, you need to supply the ‘locations’ argument.

The optional ‘locations’ argument specifies AxisValue Format 4 tables. It should be a list of dicts, where each dict has a ‘name’ item, which works just like the value dicts above, an optional ‘flags’ item (defaulting to 0x0), and a ‘location’ dict. A location dict key is an axis tag, and the associated value is the location on the specified axis. They map to the AxisIndex and Value fields of the AxisValueRecord.

Example:

locations = [
    dict(name='Regular ABCD', location=dict(wght=300, ABCD=100)),
    dict(name='Bold ABCD XYZ', location=dict(wght=600, ABCD=200)),
]

The optional ‘elidedFallbackName’ argument can be a name ID (int), a string, or a dictionary containing multilingual names. It translates to the ElidedFallbackNameID field.

The ‘ttFont’ argument must be a TTFont instance that already has a ‘name’ table. If a ‘STAT’ table already exists, it will be overwritten by the newly created one.