Emacs, meanwhile, has a 50,000 line file that contains its display and redisplay logic: https://github.com/emacs-mirror/emacs/blob/master/src/xdisp..... (It's actually a pretty readable well-commented file all things considered, but famously difficult to hack on.)
I think I'd rather have that than the state of the art in "modern" TUIs, which is to do the opposite and treat the terminal as a special case of React canvas, redrawing the whole damn thing every time there is a keystroke or other action by you or the program. You can see Claude Code redraw itself all the time; it's maddening. And the program would absolutely be unusable on, say, a 9600bps connection, whereas Emacs could still get by on that. This is from the company that retains the best and brightest programmers, and will have self-improving runaway genius AI by Christmas, for realsies this time.