[GiovanniP]

> It has superb output quality but the programming is awful

TeXmacs (http://www.texmacs.org/) has better output quality and nicer programming (it is Scheme :-) ) and it is easier to use.

[patrickg]

In which sense “better output quality”?

[GiovanniP]

Various senses that concur. It has, in addition to the line-breaking algorithm, a global page-breaking algorithm ... and for the rest may I suggest reading (it's brief) section 4.2 of GNU TeXmacs, A free, structured, wysiwyg and technical text editor, J. Van der Hoeven, Cahiers GUTenberg, no. 39-40 (2001), pp. 39-50, that you can find at the official website of the journal at http://www.numdam.org/article/CG_2001___39-40_39_0.pdf

And also looking at https://www.jonmsterling.com/papers/sterling:2022:wg6.pdf, I find it beautiful ... but perhaps there are better judges.