dev/tools/gen_keycodes/data/gtk_modifier_bit_mapping.json

{
  "SHIFT": ["ShiftLeft", "ShiftLeft", "ShiftRight"],
  "CONTROL": ["ControlLeft", "ControlLeft", "ControlRight"],
  "MOD1": ["AltLeft", "AltLeft", "AltRight"],
  "META": ["MetaLeft", "MetaLeft", "MetaRight"]
}