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In my daily work, I often ssh to a remote server using a terminal emulator. My local machine is a Windows 10 desktop. In this post, I want to share how to make true color work across terminal emulator, nvim and tmux.

Pick a suitable terminal emulator
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Not all terminal emulators support true colors. First, we need to use a terminal emulator that supports true colors. Both zoc terminal and xshell can support this.

To test whether true color works or not, run the following script on the command line:

awk 'BEGIN{
    s="/\\/\\/\\/\\/\\"; s=s s s s s s s s;
    for (colnum = 0; colnum<77; colnum++) {
        r = 255-(colnum*255/76);
        g = (colnum*510/76);
        b = (colnum*255/76);
        if (g>255) g = 510-g;
        printf "\033[48;2;%d;%d;%dm", r,g,b;
        printf "\033[38;2;%d;%d;%dm", 255-r,255-g,255-b;
        printf "%s\033[0m", substr(s,colnum+1,1);
    }
    printf "\n";
}'

If you can see a smooth color band, then true color has been activated successfully.

Enable true color in terminal emulator
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In zoc terminal, true color support is enabled by default. Previously, true color support is missing in xshell. The latest version of xshell (xshell 7) has added support for true color, but this feature is disabled by default.

To enable true color support in xshell, go to Tools --> Options, click the Advanced Tab page, under Terminal section, check the box Use true color. We need to restart xshell to activate this feature. Open a source code file using nvim, you should see that true color is working properly.

Make true color work with tmux and nvim
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However, if we use nvim inside tmux, the colorscheme is still not right. In order to make true color work inside tmux, we need a few more configuration.

Set TERM environment variable
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The correct way to set the TERM variable is via the terminal emulators.

For zoc terminal, go to Options --> Edit Session Profile. Click Emulations, in the left, choose Xterm from the list of emulations. Check TERM box below, and set it to xterm-256color. On the right, also check the box 256 color support (TERM=xterm-256color).

For xshell, edit the properties of current session (File --> Current Session Properties). Click the Terminal category, and change Terminal Type to xterm-256color.

Restart the current connection. Run command echo $TERM to verify that TERM varialbe has been correctly set to xterm-256color.

Configure tmux
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Open tmux config (in $HOME/.tmux.conf) and add the following settings:

# True color settings, see https://jdhao.github.io/2018/10/19/tmux_nvim_true_color/ for the details.
set -g default-terminal "screen-256color"

# If terminal supports true color, use the following options.
set -ga terminal-overrides ",xterm-256color*:Tc"

After these two steps, kill tmux server and start a new tmux session: