I have developed a JavaScript library called JustyKhatt, which performs line justification at the DOM layer (in the browser) by leveraging OpenType and Variable Font capabilities.

While my initial focus has been on the Arabic script, the architecture is intentionally script-agnostic. The codebase separates the generic processing Core from independent Rule Packs. The Core handles measurement, tagging, and rendering, while Rule Packs (e.g., Naskh, Nastaliq) contain the specific calligraphic logic and decision-making for each script.

The architecture documentation (ARCHITECTURE.md) and the full source code are available here:
https://github.com/AzizMohseny/FFB/tree/main/justykhatt

You can test the behavior of the engine with your own text in the live sandbox here:
[لینک ورسل خود را اینجا بگذارید، مثلاً https://justykhatt.vercel.app]

I would be very grateful if fellow type designers and engineers could test this tool and share their technical feedback. I do not have the financial means to compensate you for your valuable time, but I am more than willing to reciprocate by offering my time, advice, or expertise on your own projects whenever you might need it.

Thank you,