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@andersevenrud
Last active July 12, 2024 19:54
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True Color (24-bit) and italics with alacritty + tmux + vim (neovim)

True Color (24-bit) and italics with alacritty + tmux + vim (neovim)

This should make True Color (24-bit) and italics work in your tmux session and vim/neovim when using Alacritty (and should be compatible with any other terminal emulator, including Kitty).

Testing colors

Running this script should look the same in tmux as without.

curl -s https://gist.githubusercontent.com/lifepillar/09a44b8cf0f9397465614e622979107f/raw/24-bit-color.sh >24-bit-color.sh
bash 24-bit-color.sh

colors

Configuration files

⚠️ IMPORTANT ⚠️ Don't set $TERM in your shell (zshrc, bashrc, etc.), but your terminal (alacritty).

Alacritty

In ~/.config/alacritty/alacritty.yml:

env:
  TERM: xterm-256color

tmux

In ~/.tmux.conf (or ~/.config/tmux/tmux.conf):

set -g default-terminal "tmux-256color"
set -ag terminal-overrides ",xterm-256color:RGB"

# Or use a wildcard instead of forcing a default mode.
# Some users in the comments of this gist have reported that this work better.
#set -sg terminal-overrides ",*:RGB"

# You can also use the env variable set from the terminal.
# Useful if you share your configuration betweeen systems with a varying value.
#set -ag terminal-overrides ",$TERM:RGB"

vim

In ~/.vimrc:

" You might have to force true color when using regular vim inside tmux as the
" colorscheme can appear to be grayscale with "termguicolors" option enabled.
if !has('gui_running') && &term =~ '^\%(screen\|tmux\)'
  let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum"
  let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"
endif

syntax on
set termguicolors
colorscheme yourfavcolorscheme

neovim

If you use ~/.vimrc for your nvim configuration, use the above vim example because it's fully compatible.

💡 neovim recently (Dec 6th 2023) merged some changes that detects termguicolors automatically, so there's no need to set this in an upcoming release. I'll update this notice with a version once released as a public version. This came with the 0.10 release (May 16th 2024).

In ~/.config/nvim/init.vim

set termguicolors
colorscheme yourfavcolorscheme

Or ~/.config/nvim/init.lua:

vim.o.termguicolors = true
vim.cmd'colorscheme yourfavcolorscheme'

Not working correctly ?

Check out the comments below for possible solutions.

And if you found another solution I would really appreciate if you left a comment with instructions and the following information:

  • OS/Distro + version
  • Vim or Neovim + version
  • Terminal name + version

Mentions

Shout-out to the nice folks that provided insightful feedback:

@mikeslattery
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mikeslattery commented Dec 13, 2023

Looks like I wasn't correct. You still need the tmux and alacritty config. You just don't need the neovim config anymore.

Quick test for Linux. As of this comment it works for nightly and not for release.

#!/bin/bash
# Test for truecolor.  Should see bands of smooth gradient colors.

# To test  installed nvim, set this to "nvim" and comment out #linux nvim install block, and remove rm $NVIM line
NVIM=/tmp/nvim

# Linux nvim install
NIGHTLY=https://github.com/neovim/neovim/releases/download/nightly/nvim.appimage
RELEASE=https://github.com/neovim/neovim/releases/download/stable/nvim.appimage
# Change to $NIGHTLY to see it working correctly.
curl -Lo $NVIM $RELEASE
chmod +x $NVIM

# Reconfigure
echo '
set -ag terminal-overrides ",xterm-256color:RGB"
' > /tmp/.tmux.conf
echo '
env:
  TERM: xterm-256color
' > /tmp/alacritty.yaml

# Test
TEST=https://gist.githubusercontent.com/lifepillar/09a44b8cf0f9397465614e622979107f/raw/24-bit-color.sh
alacritty --config-file /tmp/alacritty.yaml \
  -e tmux -f /tmp/.tmux.conf -L nvim new-session \
  $NVIM --clean  "+terminal curl -s $TEST | bash" "+set termguicolors?"
# old way:
# $NVIM --clean  +"set termguicolors" "+colorscheme ron" "+terminal curl -s $TEST | bash"

# Cleanup
rm "$NVIM"
rm /tmp/.tmux.conf /tmp/alacritty.yaml

@andersevenrud
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Author

Appreciate the detailed follow-up on this @mikeslattery. I've updated the article to reflect this 👍

@n0099
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n0099 commented Feb 29, 2024

echo 'set -as terminal-overrides ",'"$(echo ${TERM%%-*})"'*:Tc"' >> ~/.tmux.conf

https://github.com/tmux/tmux/wiki/FAQ#how-do-i-use-rgb-colour

tmux must be told that the terminal outside supports RGB colour. This is done by specifying the RGB or Tc terminfo(5) flags. RGB is the official flag, Tc is a tmux extension.

With tmux 3.2 and later this can be added with the terminal-features option:

set -as terminal-features ",gnome*:RGB"

Or for any tmux version the terminal-overrides option:

set -as terminal-overrides ",gnome*:Tc"

and replace gnome with the result of echo ${TERM%%-*} (the first part of $TERM delimited by -) from the terminal emulator that you are currently using outside tmux such as putty or xterm.

@ferBV
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ferBV commented Mar 24, 2024

Just what I needed, thank you a lot.

@RobertMiguel
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My configuration:

alacritty 0.13.2
NVIM v0.9.5

.tmux.conf

# Fix Colors
set -g default-terminal "screen-256color"
set -ag terminal-overrides ",xterm-256color:RGB

alacritty.toml

[env]
TERM="xterm-256color"

config neovim

vim.opt.termguicolors = true

@zachliu
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zachliu commented Jun 3, 2024

My configuration:

zsh 5.9
tmux 3.4
alacritty 0.13.2
NVIM v0.10.0-dev-3135+g7acf39dda

.tmux.conf

set -g default-terminal "tmux-256color"
set -sg terminal-overrides ",*:RGB"

.config/nvim/init.vim

if $COLORTERM ==# 'truecolor'
  set termguicolors
else
  set guicursor=
endif

nothing special on alacritty.toml and .zshrc
i didn't set env TERM explicitly. but i have

$ env | rg TERM
COLORTERM=truecolor
TERM=tmux-256color
TERM_PROGRAM=tmux
TERM_PROGRAM_VERSION=3.4

@rdyson
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rdyson commented Jun 8, 2024

Thanks for this!

@dffuller
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@LeFede This worked for me with Arch/Alacritty/tmux

alacritty.yaml

env:
  TERM: alacritty-direct

tmux.conf

set-option -a terminal-overrides ",alacritty:RGB"

default-terminal was not needed in the tmux.conf

This worked for me. Thanks so much for adding this information!

@rogerneel
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On a Wayland / Hyprland setup

My .tmux.conf only has the line:

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

I added to alacritty.toml, which seemed to be the key:

[colors]
transparent_background_colors = true
[window]
opacity = 0.8

Immediately both neovim and tmux started showing transparency. I did not have to explicitly set vim.opt.termguicolors = true in my neovim conf.

@delatorrejuanchi
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I've only added the following to alacritty.toml (i.e.: using a default tmux config) and it seems to work as expected.

[env]
TERM = "alacritty-direct"

Undercurls, italics, bold, strikethrough, etc. also work.

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