Export font metadata (open type features)

Scripting
1

Hello!

I’m looking for a way to export metadata of all open type features in a font.

I wrote a script, which loops through all glyphs and outputs the information as JSON.
Example for a single glyph:

{
  "category": "Letter",
  "index": 302,
  "name": "Oslash",
  "features": "",
  "unicode": "00D8",
  "subCategory": "Uppercase"
}

So far so good, but what I want to achieve is:
Get the information, in which open type feature a particular glyph is used.

E.g.:

"features": ["ss01", "salt"]

The only possibility I see is looking in Glyphs.font.features.code and extract the information.
But… this feels terribly wrong and might lead to errors/bad data.

Is there ANY possibility to get these information?

Thanks,

Robert

2

That is rather complex. You could try to parse the compiled GSUB lookups but that is still quite difficult. the font object has a property tempOTFFont. You might need to initialise is by calling font.compileTempFontError_(None). Then use fonttools to parse the font and have a look at its lookups.