googlefonts/glyphsLib

Problems going from UFOs to .glyphs using v3 file format

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#754 opened on Dec 1, 2021

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Description

Using v6.0.0 I've been looking at Glyphs v3 file format support.

I see that ufo2glyphs does not currently have an option to output in v3 file format. I created an edited version to test with by adding font.format_version = 3 prior to the font.save section and successfully created a v3 format .glyphs file from a design space file. Is that the correct approach to use to create v3 format files?

Round-tripping using that and then glyphs2ufo produced many differences. Some examples are:

  • postscriptBlueValues, postscriptStemSnapH and postscriptStemSnapV removed from fontinfo.plist
  • styleName in fontinfo.plist changed to Regular for all styles
  • com.schriftgestaltung.weight in lib.plist changed to Regular for all styles
  • public.verticalOrigin added to the lib of all .glif files

Note with the postscript keys, this data does end up in a .glyphs file if it is produced by saving from the Glyphs App - for example blue values end up in Alignment Zones.

Contributor guide

Research direction
Compare the current ufo2glyphs conversion code with the Glyphs v3 file format specification. Trace where postscriptBlueValues, styleName, com.schriftgestaltung.weight, and public.verticalOrigin are handled differently between v2 and v3 output.
Tech stack
python
Domain
backendtooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
PythonFont file formats (UFO, Glyphs)
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40