Unable to write GSUB lookup type 6 tables.

[shabeernotion]

Expected Behavior

I have loaded Ribeye-Marrow-regular.ttf font and trying to font.toArrayBuffer() on Aws

Current Behavior

It throws following error:
Unable to write GSUB lookup type 6 tables.

[Jolg42]

Hi @shabeernotion

So you could check https://github.com/nodebox/opentype.js/blob/master/src/tables/gsub.js
Reading of all GSUB types 1,2,3,4,5,6,7,8 are supported but only types 1,3,4 for writing.

Feel free to contribute and add the type 4 if you need it 😉

[shabeernotion]

May I know how to add type 2 and type 6?

[Jolg42]

So for adding the support for these 2 types you'll need to check how the reading part was done and read the OpenType specification to understand how it works.
After that write your code and make sure it works well (reading / writing).

It's easier as the reading part is implemented but still need to be done 😉

[shabeernotion]

Should I implement in order to parse? Are there any other way that I can parse without doing it?

[Jolg42]

So parsing is already implemented actually!

[shabeernotion]

Yeah but actually this error throws on toArrayBuffer(). So, If it's throws an error, I hope it won't parse correctly.

[Jolg42]

Yes indeed, so what's happening is that toArrayBuffer() is trying to write the GSUB type 6 that was read when loading the font and it can't because it's not implemented.
Basically opening is working but when doing toArrayBuffer() you ask to convert the data back to a font format and it can't.

[Connum]

I've got writing for GSUB type 6 format 1 and 3 working so far:
https://github.com/Connum/opentype.js/tree/add-lookup-type-6
Testing and feedback is encouraged and would be great to have before creating a PR.