Trying to highlight text sometimes highlights too much when terminal is very active

Thanks for filing an issue! Please answer the questions below so I can help you.

• iTerm2 version: 3.0.15
• OS version: 10.12.6
• Attach ~/Library/Preferences/com.googlecode.iterm2.plist here (drag-drop from finder into this window)
• Attach a debug log, if possible. Instructions at https://iterm2.com/debuglog

Detailed steps to reproduce the problem:

1. Have a very busy terminal, with a few lines per second scrolling. Hard to know the exact number, maybe 5-10/second.
2. Pause scrolling by scrolling the window up to a line you want to copy, using either the mouse wheel or the scroll bar in the iTerm window.
3. Use mouse to try to highlight a small amount of text.

What happened: The mouse highlight jumps and highlights multiple lines. This happens only when a lot of lines are coming from the remote server, not when it's fairly slow. I can say that 1-3 lines per second is never a problem, but 10+ seems to be every time. See attached screen grab, I was attempting to highlight only the IP address for investigation. This is repeatable when the terminal is very busy.

What should have happened: Highlight only desired text.

com.googlecode.iterm2.plist

This is because I'm not using absolute line numbers in selections. If scrollback history has overflowed then it'll change by the number of lines lost. I need to fix this but it's a big project.

changed milestone to %Review for next version