An interactive introduction to the terrific experience of rendering Arabic typography and its technical debt

The history deserves recording because most people outside the small world of Arabic font engineering don't know it, and it is wonderful. Classical Arabic typography, by which I mean the manuscript tradition that the early printers of Istanbul and Bulaq spent their careers chasing, justifies a line of text without stretching the spaces between words at all. Stretched spaces are the Latin convention, and in Arabic they produce an effect the scribes would have found simply ugly. Instead the scribe extends the letterforms themselves along the baseline, using what is called taṭwīl or, in the modern technical vocabulary, kashida: the connecting strokes between certain pairs of letters can be lengthened, sometimes lavishly, to carry a line out to the margin. A well-set page of Naskh from the seventeenth century has every line flush at both margins, and the result is the dense, regular weave that anyone who has spent time with a good manuscript Qurʾān will recognise on sight. [...] The one…