using Mutt, line drawing characters change when iTerm2 window is idle

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

• iTerm2 version: Build 3.2.20180712-nightly

• OS version: 10.13.5[com.googlecode.iterm2.plist]

• Attach ~/Library/Preferences/com.googlecode.iterm2.plist here (drag-drop from finder into this window)(/uploads/bc0d632c7358b20b27144409d6736157/com.googlecode.iterm2.plist)

• Attach a debug log, if possible. Instructions at https://iterm2.com/debuglogdebuglog.txt

• Are you reporting a performance issue or a hang? Please attach a sample. Instructions at https://gitlab.com/gnachman/iterm2/wikis/HowToSample

• Are you reporting a crash? Please attach the crash log. Instructions at https://gitlab.com/gnachman/iterm2/wikis/crash-logs

• Are you reporting excessive memory usage? Please attach a heap analysis: https://gitlab.com/gnachman/iterm2/wikis/heapshot

Detailed steps to reproduce the problem:

1. cat this attached edited typescript of a Mutt session.ld5.txt
2. Wait a few seconds.
3. Type a character.

What happened:

After a few seconds of idleness, the line drawing characters displayed change (dim or thin). On striking a key and waking up the session, the line drawing characters change back. Video: iterm2-line-draw

What should have happened:

The line drawing characters should not have changed. If you disable the "Disable Metal when idle" preference, they don't change, obviously suggesting some difference between the Metal and non-Metal renderers.