One thing that's a little tricky is once you do that, the real code doesn't match what's on the screen. Not so bad if it's just whitespace, a little worse if you have to add characters to allow the line breaks. Still, I'd like it and would probably use it. I'm sort of a sadist in that I like 120 width, even though I can't quite go 2 windows wide on my laptop. I just side scroll like a peasant.

Xcode on OS X has been doing this for at least one decade.

http://journal.stuffwithstuff.com/2015/09/08/the-hardest-pro... might explain why 'just' doing the pretty print on the fly might not be a easy thing (even if the problem here is limited to a single line of code and something based on line length).