Add check to ensure a glyphs source file conforms to the file format schema

[felipesanches]

googlefonts/glyphsLib#332 (comment)

[felipesanches]

is it an opportunity to bootstrap a check-glyphsapp profile with source-level checks for Glyphs project files?

[felipesanches]

@schriftgestalt, this reminds me of a conversation I had with @mekkablue last year in São Paulo, Brazil, in which he expressed interest in having FontBakery embedded into GlyphsApp to run checks automatically as designers work on their fonts.

We could create a glyphsapp profile that would be enabled by default and then let users tweak settings if they want to enable other check profiles as well.

[felipesanches]

@schriftgestalt, do you have runtime GlyphsApp quality checks that you'd be happy if we ported into FontBakery?

[schriftgestalt]

I don’t have interesting test. Just a few basic sanity test. I’ll see if I find something.

Adding more test was always on my list.

[felipesanches]

We now can run checks agains glyphs source files in fontbakery.

An initial implementation for this check might be straightforward: does the file parse without errors when loading it with GlyphsLib?

[schriftgestalt]

There is a validator in https://github.com/schriftgestalt/GlyphsSDK/tree/Glyphs3/GlyphsFileFormat/validator That might be useful.

[simoncozens]

What's the rationale for this? Because if Glyphs (or even glyphsLib) is authoring files that don't conform to its own schema, that isn't something that the designer can fix.

[schriftgestalt]

It might be useful to cast a wider net to catch a) problems with Glyphs/glyphsLib or b) to find issues with schemes. It would be better put into the respective unit test but here it gets more exposure.