Historical flavor: At CMU in the mid-80s, I was interested by the Gosling Emacs redisplay algorithm, which was essential in making Emacs usable on the 1200 baud terminals in the CS department. Gosling was working on the text editor for the Andrew system at the time, and I was curious to see how he would adapt redisplay to a bitmapped display. But I found out the Sun workstation was “so fast” that he hadn’t bothered, it just redrew the entire line every time.