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Glyph Construction

Glyph Construction is a simple, powerful, human-readable language for describing how glyph shapes are built.

Glyph Construction can be used to create new glyphs from components. It is specially useful for creating accented glyphs.

Collections of Glyph Construction rules can be saved as *.glyphConstruction files, and can be shared between fonts.

This repository contains:

glyphConstruction module
A Python library to parse glyph construction rules and build new glyphs in a given font.
Glyph Construction extension
A RoboFont extension which includes the Glyph Builder, a visual glyph construction editor with live preview.

Table of Contents

Glyph Construction language

Assigning a construction to a glyph

Build <destGlyphName> out of one or more components.

<destGlyphName> = <glyphName> + <glyphName>
Aacute = A + acute

Optionally, a suffix can be provided. If a glyph with the given suffix does not exist in the font, the suffix is ignored.

Aacute = A + acute.cap


A line starting with (or anything after) a # is a comment and will not be used during execution.

# this is a comment
Aacute = A + acute
Agrave = A + grave # this is a note


A comment # at the end of a glyph construction is a note.

<destGlyphName> = <glyphName> + <glyphName> # <note>
Aacute = A + acute # this is a note


Unicodes in hexidecimal notation. Multiple Unicodes accepted, separated by commas. Glyph Builder: If Unicodes are provided, they will be used even if "AutoUnicodes: True" is set.

<destGlyphName> = <glyphName> + <glyphName> | <unicode>, <unicodes>*
Aacute = A + acute | 00C1
Tcommaaccent = T + commaaccent @ bottom | 021A, 0162

Mark Color

<destGlyphName> = <glyphName> + <glyphName> ! <rgba>
Aacute = A + acute ! 1, 0, 0, 1



<destGlyphName> = <glyphName> + <glyphName> ^ <width>
Aacute = A + acute ^ 400

Left and Right Margins

<destGlyphName> = <glyphName> + <glyphName> ^ <leftmargin>, <rightMargin>
Aacute = A + acute ^ 30, 30

Width and margin values can also be defined using basic maths and references to width, leftMargin or rightMargin of other glyphs.

# width is equal to twice the width of A
Aacute = A + acute ^ A * 2

# left margin is equal to one third of the left margin of A
# right margin is equal to twice the right margin of B
Aacute = A + acute ^ A / 3, B * 2

Use a ' to flip to the opposite side of given glyph margin.

# left margin is used for the right margin of the generate d.alt
d.alt = d ^ d', d'

Use " to explictly provide a glyph name, required to use " for each named glyph name. Glyph names can contain math symbols like -, +, *.

# left and right margins is used from a explict glyph name.
A = ^ "T", "T-1" * 2

Decompose glyph

Add * before a glyph construction rule to explicitly tell the constructor to decompose the final result.

*agrave = a + grave

Add Source Glyph

Add > before a glyph construction rule to include the source font glyph name in the final result.

# include the the drawing of the source font 'a'
# and set the spacing to 40 for the left margin and 50 on the right margin.
>a = ^ 40, 50

Ignore existing glyphs

Add ? before a glyph construction rule to ignore this glyph if it already exists in the font.

?Aacute = A + acute


The Glyph Construction language offers different ways to position the added components in relation to the current glyph.

By Numbers

Aacute = A + acute@100
Aacute = A + acute@100,100

By Percentages

Aacute = A + acute@50%,50%

By Reference

Aacute = A + acute@center,top

A reference could be (in this order):

  • double anchor (with the _<anchorName> notation)
  • a single anchor name
  • a local guide name
  • a global guide name
  • a font dimension attribute: descender, xHeight, capHeight, ascender
  • a calculated reference position: top, bottom, left, right, innerLeft, innerRight, center, origin, width

By Transformation Matrix

@ followed by a transformation matrix: 6 values xx, xy, yx, yy, x, y

Aacute = A + acute@1, 0, 0, 1, 100, 100

Change the current glyph

The current glyph is always the last component added.

For example, Aacute = A + acute will:

  • add component with name A (there is no current glyph)
  • add component with name acute (the current glyph is A)

Force the current glyph with @<glyphName>:<pos>:

Ocircumflexdotaccent =  O + circumflex@center,top + dotaccent@O:center,bottom

The forced glyphName can also be escapped with " in case the glyph name contains a :

Ocircumflexdotaccent =  O + circumflex@center,top + dotaccent@"O:latn":center,bottom


~ followed by a position will flip a component:

# flip horizontally
Aacute = A + acute@~center,top

# flip vertically
Aacute = A + acute@center,~top

# flip both horizontally and vertically
Aacute = A + acute@~center,~top

Stacking Vertically

Aringacute = A + ring@center,top + acute@center,top

Positioning formulas

Aringacute = A + ring@center,`top+10` + acute@center,`top-10`

Stacking Horizontally

ffi = f & f & i

Apply kerning while stacking horizontally

Start a sub-glyphConstruction with a backslash to indicate kerning should be applied while stacking horizotally.

A_V = A &\ V


Glyph Construction supports variables, which can be defined once at the top of the document and used multiple times.

$name = something # declaration
{name} # usage

$myColorMark = 1, 0, 0, 1 # declaration
agrave = a + grave@center,top ! {myColorMark} # usage

Glyph Builder interface

To install the Glyph Construction extension in RoboFont, follow the instructions provided in the links below:

Once the extension is installed, the Glyph Builder can be opened from the menu Extensions > Glyph Construction. Saved .glyphConstruction files can be opend directly in RoboFont by dragging the file on RoboFont.

Here’s a description of each part of the Glyph Builder interface:


The toolbar at the top of the window gives access to the following actions:

Save all rules as a .glyphConstruction file.
Open an existing .glyphConstruction file.
Update the contents of the Preview and Analysis columns.
Show/hide the Analysis column.
Build Glyphs
Build all described glyphs in the current font.
Build only the selected glyph.

Rules editor

The left column contains a simple text editor where Glyph Construction rules can be written, one per line.

See Glyph Construction language for syntax documentation and examples.


The middle column displays a preview for every glyph construction rule defined in the left column.

The preview supports zooming in/out with ⌘ +/- keys or with the mouse.

Individual glyphs can be selected with a click – see Selection preview (below).


The right column displays useful information about the glyph construction rules defined in the editor: missing and existing glyphs, existing glyphs with missing components, and existing glyphs with different components.

Selection preview

At the bottom of the right column is a preview of the glyph which is currently selected in the preview area.

If the glyph already exists in the font, its current shape is displayed in the background in red for comparison.

Status bar

The status bar at the bottom of the window displays information about the currently selected glyph: glyph name, width, left and right margins, component names, unicode, mark color, and note.

Comment variables

Preset build checkboxes in the comments of the constructions.

# OverwriteExistingGlyphs: True/False
# AutoUnicodes: True/False
# MarkGlyphs: False/r, g, b, a