Why aren't my screen-drawing apps drawing under tmux?

Question

I'm running tmux version 2.3 on Raspbian 8 and I've had some weirdness happen. Namely, many windows that should be redrawing the screen apparently aren't, and I'm not sure why. Examples of apps that aren't:

• aspell -c
• irssi
• termdown -b

In each of these cases I observe different but odd behavior.

For aspell when it scrolls the window the only thing that is redrawn is the bottom box where the suggestions are and the error words. But they'll be drawn in weird places on the screen, sometimes in the middle of the other words. Ctrl+L does not work here (says it's an unknown key). Here's what that looks like:

In irssi when the conversation reaches the bottom of the window every line above the most recent one becomes frozen. Ctrl+L works here.

Termdown with -b is supposed to make the screen blink red. It doesn't.

The problem is definitely related to tmux. Any of the commands without tmux are A-OK. Termdown blinks, aspell redraws everything, and irssi updates live.

I've checked and even without a .tmux.conf I still get the same behavior, so nothing there appears to be triggering it.

What in the world could be causing such a bizarre thing to happen?

Answer 1

Each tmux pane emulates a terminal, and emulation is not the same thing as an xterm. The emulation in tmux needs to match screen, a different terminal description, to behave properly; but, the real terminal does not need to do so. The terminal's description is xterm-256color, so in ~/.tmux.conf, set the terminal description to match the colors in the xterm terminal.

set -g default-terminal "screen-256color"