This is sort of a sub-case of #318 that feels like it could be an easier fix.

Perhaps we could avoid redrawing the terminal if the updated lines fall outside the current viewport. I'm not sure if this would be an easy fix so please close this issue if time would be better spent pursuing a proper fix for #318 etc.

Big use case here is scrolling back through tail -f'd logs and trying to copy and paste them.

Details

• Browser and browser version: Chrome Version 55.0.2883.95 (64-bit)
• OS version: OSX 10.11.6 (15G1108)
• xterm.js version: 2.2.3

Steps to reproduce

1. while true; do echo 1; sleep 1; done
2. Wait for echos to hit the bottom of the term.
3. Scroll back up, so that terminal appears fairly static (new echos are coming in below the last visible line).
4. Try and select text - selection is lost on next echo

Cheers!