Extremely slow performance with ANSI escapes with some Unicode code points

• iTerm2 version: 3.0.4
• OS version: 10.11.5
• Attach ~/Library/Preferences/com.googlecode.iterm2.plist here (drag-drop from finder into this window) com.googlecode.iterm2.plist
• Attach a debug log, if possible. Instructions at https://iterm2.com/debuglog debuglog.txt
• Are you reporting a performance issue? Please attach a sample. Instructions at https://gitlab.com/gnachman/iterm2/wikis/HowToSample Sample_of_iTerm2.txt

Detailed steps to reproduce the problem

1. Create the following script:

   #!/usr/bin/env bash
   tput bold
   for i in `seq 1 10000`; do
     echo -n '\xE2\x95\x8E'  # box drawings light double dash vertical (U+254E)
     (( $i % 72 )) || echo
   done
   tput sgr0
   echo

2. Run it.

What happened

iTerm2 comes to a screeching halt. (You might be able to Ctrl+C/Cmd+K to regain control.) The larger the number of characters written, the worse the performance. Also happens with other ANSI codes like tput dim instead of tput bold.

What should have happened

iTerm2 should continue to run normally.

Drawing lots of small attributed strings is just dying. Hopefully the fix for ligatures fixes this too. I'll take another look after #3568 (closed) is closed.

Milestone changed to %Feature Complete 3.1

mentioned in issue #5102 (closed)

Seems instant now, probably because of adaptive framerates.

closed