Mouse events not working in Vim on Debian?

Question

If I click on a line, I can see "19m" or "18m" etc. show up in the bottom right of the screen. If I scroll, nothing happens, but shift+click&drag works.

set encoding=utf8                                                                                    
set ttym=xterm2
set mouse=a

I've tried a few variations of the above but nothing looks different.

I'm using a config file that worked on Ubuntu, so this change is odd.

I'm using the Tilda terminal emulator, with tmux inside, to interact with vim. Specifically, tmux -2 wrapped around zsh running vim.

bash TERM=mlterm, tmux/zsh TERM=xterm-256color

Answer 1

The TERM environment variable controls what character sequences are sent and received by programs and the proper value depends on the terminal emulator. Inside tmux, you generally want one of the tmux-* or screen-* values, preferably the former. If you change to the correct terminal type, this will probably work as expected.

In most cases, tmux-direct is the most featureful (it supports true colour), but not all systems support it. tmux-256color is an option on many modern systems, and you can also use screen-256color in a pinch. To verify whether a terminal definition is available on your system, you can run infocmp tmux-direct (or whatever value you like) and that will either print the definition (if it's available) or a message that it's not available.

Note that if you SSH into older machines, it may be better to set one of the 256-colour modes instead of tmux-direct since the TERM setting is copied over by default and having a value that doesn't exist on the machine can break most terminal-using programs, including your shell.

To set the default terminal type in tmux, you can use set -g default-terminal tmux-256color in ~/.tmux.conf.