You can check the Pango's script gallery (GNOME project) [0] as showcase of their prowess to be able to render Persian/Urdu that is the most complex form of Arabic script.

Complexity comes from the fact that in Arabic, a single character can have at max 4 contextual shapes generally speaking. In Nastaleeq variation, a single character can have up 100s of contextual shapes depending upon where it appears in the word.

[0]. https://pango.gnome.org/ScriptGallery

This has been linked in the comments already, but check this out: https://faultlore.com/blah/text-hates-you/

That's an interesting read, but I didn't find anything relating to

> ascend upwards depending upon the length of the word

Did I just miss it?