Comment 4 for bug 1902643

Caught centos8 tmux (2.7-1.el8.x86_64) a couple times dropping out of copy mode apparently in response to window size changes while showing a different tmux window, tho now when i repeat what i thought was the trigger sequence i can't repeat it again. Of course i was hoping to catch focal tmux in the act of dropping out of copy mode, but not yet today.

Meanwhile i do observe focal tmux (3.0a-2ubuntu0.1) oddly changing the window size by one line and changing it right back again in response to window size changes while showing a different tmux window. to wit:

 $ alias ws='c=;while ((c==COLUMNS&&l==LINES))||{ c=$COLUMNS l=$LINES;echo $(date +%F%a%T) ${l}x$c;};do sleep .05;done' #track window size changes
 $ ws
2020-11-04Wed15:43:52 57x226
2020-11-04Wed15:44:00 24x80
2020-11-04Wed15:44:01 57x226
2020-11-04Wed15:44:15 56x226
2020-11-04Wed15:44:15 57x226

'24x80' was when i unmaximized the xterm, and '57x226' when i remaximized it a second later, without changing the tmux window meanwhile. However then i switched to show a different tmux window, unmaximized, remaximized, and then when i switched the tmux window back, you see the odd little dance where tmux changes by one line to '56x226' and immediately back to '57x226'.