theme-mode

#!/usr/bin/env bash
#
# Set or toggle light/dark themes on desktops with xsettingsd.
#
# Copyright (C) 2017-2023 Rafael Cavalcanti <https://rafaelc.org/dev>
# Licensed under GPLv3

readonly config_path="$HOME/.config/theme-mode/config"
readonly xsettingsd_config="$HOME/.config/xsettingsd/xsettingsd.conf"

main() {
  if [[ $# -ne 1 ]]; then
    usage
  fi

  check_desktop
  get_config
  set_target "$1"
  apply
}

usage() {
  printf "Usage: %s <light|dark|toggle>\n" "$(basename "$0")"
  exit 1
}

log() {
  printf "%s\n" "$*" 1>&2
}

get_config() {
  if [[ ! -e "$config_path" ]]; then
    printf "Config not found at %s.\n" "$config_path"
    exit 1
  fi
  source "$config_path"
}

check_desktop() {
  if ! pidof xsettingsd > /dev/null; then
    log "This desktop is not supported."
    exit 1
  fi
}

set_target() {
  case "${1:-}" in
    light)
      readonly target_theme="$theme_light"
      readonly target_icon="$icon_light"
      readonly target_scheme="prefer-light"
      readonly target_wallpaper="${wallpaper_light:-}"
      ;;
    dark)
      readonly target_theme="$theme_dark"
      readonly target_icon="$icon_dark"
      readonly target_scheme="prefer-dark"
      readonly target_wallpaper="${wallpaper_dark:-}"
      ;;
    toggle)
      set_target_toggle
      ;;
    *)
    usage
  esac
}

set_target_toggle() {
  local -r theme_current="$(awk -F' ' '/^Net\/ThemeName / {gsub("\"","", $2); print $2}' "$xsettingsd_config")"

  case "$theme_current" in
    "$theme_dark") set_target "light" ;;
    "$theme_light") set_target "dark" ;;
    *) set_target "dark" ;;
  esac
}

apply() {
  # Set on xsettingsd
  sed -i "s#^Net/ThemeName .*\$#Net/ThemeName \"$target_theme\"#" "$xsettingsd_config"
  sed -i "s#^Net/IconThemeName .*\$#Net/IconThemeName \"$target_icon\"#" "$xsettingsd_config"
  killall -HUP xsettingsd

  # Set theme on gnome
  # This is relevant on dwm because:
  # - prefer-dark sets some gnome applications to dark.
  # - gtk-theme (used for theming "legacy" apps) sets Qt
  # applications dark, since we are using qgnomeplatform.
  gsettings set org.gnome.desktop.interface gtk-theme "'$target_theme'"
  gsettings set org.gnome.desktop.interface color-scheme "'$target_scheme'"

  # Set wallpaper
  if [[ -n "${target_wallpaper:-}" ]]; then
    set-wallpaper "$target_wallpaper"
  fi
}

main "$@"