How to toggle dark and light mode for linux terminal, tmux, Vim, fish shell and Ubuntu Gnome?

Category: Terminal

You know the situation: you've worked through the night with your development system and now you need to go outside or take the train. Normally you feel comfortable with the dark mode. But suddenly you need to change it to light mode.

Introduction

By this post, I'd like to share how I switch between light and dark mode with a single script. Maybe it will help you to create your own, because it is customized for my development setup.

For development, I use the following setup:

  • OS: Linux Ubuntu (Gnome) with Wayland
  • tmux terminal emulator with powerline (source)
  • foot terminal (source)
  • theme.sh (source)
  • VI for coding (Neovim)

Bash Script

For those in a hurry, the bash script below will switch all necessary applications between light and dark mode for the above setup:

~/bin/switch_scheme.sh
#!/bin/bash
#
# Switch color scheme between light and dark for the following applications:
# * terminal (theme.sh)
# * fish
# * gnome (color scheme and gtk-theme)
# * tmux (reload powerline)
#
# Limitations:
# * Running vim sessions do not change the theme and have to be reopened


# Function for switching scheme depending on the content of the file
# ~/.colorscheme
#
# Defaults to dark and changes to light
function switch_scheme() {
  scheme=`cat ~/.colorscheme`

  # If scheme is "light", change to dark
  if [ "$scheme" = "light" ]; then
    # Select a dark theme for terminal:
    /usr/bin/theme.sh ayu

    # Set variable "background_mode" of fish. A fish config will update
    # the theme (@see ~/.config/fish/conf.d/update_theme.fish)
    fish -c "set --universal background_mode 'dark'"

    # Gnome: set preferable scheme to dark
    gsettings set org.gnome.desktop.interface color-scheme prefer-dark
    # and change the gtk-theme
    gsettings set org.gnome.desktop.interface gtk-theme 'Yaru-prussiangreen-dark'

    # Finally set the current mode to "dark"
    echo "dark" > ~/.colorscheme
  else
    /usr/bin/theme.sh selenized-light
    fish -c "set --universal background_mode 'light'"
    gsettings set org.gnome.desktop.interface color-scheme prefer-light
    gsettings set org.gnome.desktop.interface gtk-theme 'Yaru-prussiangreen'
    echo "light" > ~/.colorscheme
  fi
}

# If running inside tmux:
# * Leave tmux (detach), run this script and attach again and update powerline
if [ "$TERM" = "screen-256color" ] && [ -n "$TMUX" ]; then
  session_name=`tmux display-message -p '#S'`
  tmux detach -E "switch_scheme.sh && tmux attach -t $session_name"
  /home/mitosch/.tmux/tmux-powerline/src/powerline.sh init
else
  switch_scheme
fi

Some applications need a special setup to react on the switch.

Fish shell: Change theme interactively

To change the theme of fish, we make use of a universal variable which fish is listening to and changes the theme:

~/.config/fish/conf.d/update_theme.fish
function update_theme --on-variable background_mode
  if [ "$background_mode" = "dark" ]
    fish_config theme choose dark
  else if [ "$background_mode" = "light" ]
    fish_config theme choose light
  end
end

For this to work, you'll need those fish themes in the directory "~/.config/fish/themes":

~/.config/fish/themes
dark.theme
light.theme

Vim (Neovim): Switch dark and light themes

To start Vim with the correct colorscheme depending on the dark or light theme, the following lua script will read the content of the file "~/.colorscheme":

~/.config/nvim/lua/colorscheme.lua
-- Detect dark or light theme saved in .colorscheme. defaults to dark
local background_mode
local f = io.open(os.getenv('HOME')..'/.colorscheme', 'r')
if f ~= nil then
  background_mode = f:read('*all')
  background_mode = string.gsub(background_mode, "\n", '')
  f:close()
else
  background_mode = 'dark'
end

-- use ayu theme for dark mode, selenized for light mode
if background_mode == 'dark' then
  vim.g.ayucolor = background_mode
  vim.cmd("colorscheme ayu")
else
  vim.cmd("colorscheme selenized")
  vim.cmd("set background=" .. background_mode)
end

I'm using the ayu colorscheme for the dark mode in my terminal and Vim. In the light mode the selenized colorscheme is being used. You can find the Vim colorschemes here:

Conclusion

With a simple bash script you should now be able to change between light and dark mode. There is still a limitation for the running Vim sessions, which need to be restarted. When I find a fix in the future, I'll let you know.

To get a feeling about the setup, here you find the foot terminal in dark and light mode:

I hope this helped somebody to create an own script to change your development setup fast and efficient. It helps me every day, when the sun is shining. For feedback or suggestions, just drop me an email.