https://github.com/googlefonts/glyphslib

A bridge from Glyphs source files (.glyphs) to UFOs
https://github.com/googlefonts/glyphslib

Last synced: over 1 year ago
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A bridge from Glyphs source files (.glyphs) to UFOs

• Host: GitHub
• URL: https://github.com/googlefonts/glyphslib
• Owner: googlefonts
• License: apache-2.0
• Created: 2015-10-19T21:00:22.000Z (almost 11 years ago)
• Default Branch: main
• Last Pushed: 2025-03-24T13:15:30.000Z (over 1 year ago)
• Last Synced: 2025-04-13T04:59:37.446Z (over 1 year ago)
• Language: Python
• Homepage:
• Size: 38.3 MB
• Stars: 186
• Watchers: 41
• Forks: 52
• Open Issues: 192
• Metadata Files:
  • Readme: README.builder.md
  • Contributing: CONTRIBUTING.md
  • License: LICENSE

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README

          
# glyphsLib.builder sketch

Here is an of overview of how `glyphsLib.builder` converts a Glyphs `GSFont` object into a set of UFO and Designspace files.

## To convert each master

* Create base UFOs using the GSFont metadata and per-master metadata

    * Also store names, user data, custom parameters, custom filters

* Convert the main layer of each master; convert also bracket/brace layers. (See [To convert each layer](#To_convert_each_layer) below)

* Propagate anchors. How we should do this is… disputed.

    * [https://github.com/googlefonts/glyphsLib/issues/368#issuecomment-491939617](https://github.com/googlefonts/glyphsLib/issues/368#issuecomment-491939617)

    * [https://github.com/googlefonts/fontmake/issues/682#issuecomment-658079871](https://github.com/googlefonts/fontmake/issues/682#issuecomment-658079871)

    * We currently (but shouldn’t) find the component closest to the origin: [https://github.com/googlefonts/ufo2ft/pull/316#issuecomment-1178961730](https://github.com/googlefonts/ufo2ft/pull/316#issuecomment-1178961730)

* Store font and master userData in “layerLib” (why?)

* Convert color layer IDs into layer names if there is a mapping in com.github.googlei18n.ufo2ft.colorLayerMapping (how would there be one here at this point?)

* Convert the features into a feature file

* Apply any custom parameters to the lib, including:

    * codePageRanges/openTypeOS2CodePageRanges/codePageRangesUnsupportedBits

    * GASP table

    * Color Palettes (converted and stored in a ufo2ft key)

    * Name records

    * Don't use Production Names

    * disablesNiceNames/useNiceNames

    * "Use Typo Metrics"/"Has WWS Names" /"openTypeOS2SelectionUnsupportedBits"

    * glyphOrder

    * Filters

    * Replace Prefix / Replace Feature (modifies feature file)

    * Reencode Glyphs

* Fix up color layers:

    * Create color palette layers of {glyphname}.color{i}, convert UFO glyphs for each

    * Create COLRv1 layers, convert UFO glyphs for each and apply paint/stroke

* Write out any skipExportGlyphs list gathered when converting glyphs

* Convert feature groups and kerning groups

* Convert kerning

## To convert each layer

* For each glyph, look at all its Glyphs layers and, for master layers only, create/select appropriate UFO layers. Then convert each glyph. (See [To convert each glyph](#To_convert_each_glyph) below)

* For non-master layers, collect a list of Glyphs layers and glyphs associated with them.

* Out of that list, discard those which have no master associated with them and no name; gather up bracket layers (which will be processed during designspace generation); discard other irrelevant layers; convert other glyphs to glyphs in appropriate UFO layers.

## To convert each glyph

* For color glyphs, create a mapping between layers and palette IDs; clone any layers with components shared between them; gather into a list of color layers.

* Set unicodes

* Add to skipExportGlyphs if not exported

* Determine production name, category and subcategory; write production name into lib.

* Use category to zero out width if it’s a mark glyph; otherwise, check if the width is determined from the “Link Metrics With Master”/Link Metrics With First Master custom parameters.

* Convert hints.

* Stash any user data (is this necessary?)

* Resolve/decompose smart components (currently we just store this info - don’t do anything with it?)

* Draw paths with a pen onto the UFO glyph

* Convert any components to UFO

* Convert any anchors to UFO

* If the font is vertical, set the height and vertical origin in the UFO

## To create the designspace file

* Convert Glyphs axes to designspace axes (Looking carefully at the custom parameters “Axis Mappings”, “Axes” - for older Glyphs versions - “Axis Location”, and “Variable Font Origin”/”Variation Font Origin” (again for older Glyphs)

* Convert Glyphs masters to designspace sources

* Convert Glyphs instances to designspace instances

* Copy userdata into the designspace lib, add feature writers unless there is a manual kern feature. (this may be a bug - [https://github.com/googlefonts/glyphsLib/issues/764](https://github.com/googlefonts/glyphsLib/issues/764) )

* Extract bracket layers into free-standing UFO glyphs with Designspace substitution rules. Check the “Feature for Feature Variations” custom parameter to set the OT feature for the rule.