OTL json schema

gistfile1.txt

# Common structure for GPOS, GSUB

{
    "Version": int,
    "Scripts": [
        {
            "Tag": str,
            "DefaultLangSys": {
                "ReqFeatureIndex": int,  # is it always 0xFFFF?
                "FeatureIndices": List[int]
            },
            "LangSysRecords": [
                {
                    "Tag": str,
                    "LangSys": {
                        "ReqFeatureIndex": int,
                        "FeatureIndices": List[int],
                    }
                },
            ]
        },
    ],
    "Features": [
        {
            "Tag": str,
            "FeatureParams": Optional[FeatureParams],
            "LookupListIndices": List[int],
        },
    ],
    "Lookups": [
        {
            "LookupType": int,
            "LookupFlag": List[LookupFlag(Enum)],
            "MarkFilteringSet": int, # index into GDEF.MarkFilteringSets
            "Subtables": [
                # ...
            ],
        },
    ]
}


# GPOS

# Lookup type 2: PairPos

# PairPos format 2: Class to Class Positioning

{
    "classes": {
        "kern1.0": ["a", "b"],
        "kern2.0": ["c", "d"],
        "kern2.1": ["e", "f", "g"],
    },
    "values": {
        "kern1.0": {
            "kern2.0": -40,
            "kern2.1": 10
        },
        "kern1.1": {
            "kern2.0": 3,
            "kern2.1": -4,
        }
    }
}