could've guessed staying away from xdisp.c was a good idea, cf. the "Buttery Smooth Emacs"[0] post:

> Keep in mind that Emacs xdisp.c tries to support five different toolkits (including two different major versions of GTK) with #ifdefs. There is no runtime abstraction. We define three or four different versions of each damn function. It’s a nightmare.

[0] https://gist.github.com/ghosty141/c93f21d6cd476417d4a9814eb7...