grub-colour-chooser

#/bin/bash

# Choose grub menu colours with arrow keys in the preview.
# Changes will be saved in file /etc/default/grub.
# After reboot you'll see the changes in the grub menu.

etcdefaultgrubfile="/etc/default/grub"
grubconffile="/boot/grub/grub.cfg"

function cleanup() {
  rm -f -- "$tmpfile"
  printf '\e[?25h' # unhide cursor
  stty echo
}
trap cleanup EXIT

readonly tmpfile="$(mktemp default-grub-temp-XXXXXX)"

set -e # fail on first error

stty -echo
printf '\e[?25l' # hide cursor

CSI_fg=$'\e[38;2;'
CSI_bg=$'\e[48;2;'
esc_reset=$'\e[0m'

esc=(
  "0;0;0m"         # black
  "0;0;168m"       # blue
  "0;168;0m"       # green
  "0;168;168m"     # cyan
  "168;0;0m"       # red
  "168;0;168m"     # magenta
  "168;84;0m"      # brown
  "168;168;168m"   # light-gray
  "84;84;84m"      # dark-gray
  "84;84;254m"     # light-blue
  "84;254;84m"     # light-green
  "84;254;254m"    # light-cyan
  "254;84;84m"     # light-red
  "254;84;254m"    # light-magenta
  "254;254;84m"    # yellow
  "254;254;254m"   # white
)

# make black opaque for truecolor terminal emulators:
[[ $COLORTERM = "truecolor" ]] && esc[0]="1;1;1m"

cname=(
  "black"
  "blue"
  "green"
  "cyan"
  "red"
  "magenta"
  "brown"
  "light-gray"
  "dark-gray"
  "light-blue"
  "light-green"
  "light-cyan"
  "light-red"
  "light-magenta"
  "yellow"
  "white"
)

val=(0 9 1 11) #normal bg, normal fg, highlighted bg, highlighted fg
selected=0;

print_menu() {
  gb=$CSI_bg${esc[0]}$CSI_fg${esc[7]}
  no=$CSI_bg${esc[${val[0]}]}$CSI_fg${esc[${val[1]}]}
  hl=$CSI_bg${esc[${val[2]}]}$CSI_fg${esc[${val[3]}]}

  cat \
<< EOF
$gb          Colour Chooser for GRUB - PREVIEW           $esc_reset
$gb    $no┌────────────────────────────────────────────┐$gb    $esc_reset
$gb    $no│ Normal option                              │$gb    $esc_reset
$gb    $no│ Normal option                              │$gb    $esc_reset
$gb    $no│$hl Highlighted option                         $no│$gb    $esc_reset
$gb    $no│ Normal option                              │$gb    $esc_reset
$gb    $no│                                            │$gb    $esc_reset
$gb    $no│                                            │$gb    $esc_reset
$gb    $no│                                            │$gb    $esc_reset
$gb    $no└────────────────────────────────────────────┘$gb    $esc_reset
$gb    Use the arrow keys to change the values below.    $esc_reset
$gb    Press ENTER when done.                            $esc_reset
$gb                                                      $esc_reset
EOF

  local SO
  local SC
  SO[$selected]='>'
  SC[$selected]='<'

  printf "%s      Normal background:      %-2s%-14s%s%2s    %s\n" \
    "$gb" "${SO[0]}" "${cname[${val[0]}]}" "$CSI_fg${esc[${val[0]}]}██$gb" \
    "${SC[0]}" "$esc_reset"
  printf "%s      Normal foreground:      %-2s%-14s%s%2s    %s\n" \
    "$gb" "${SO[1]}" "${cname[${val[1]}]}" "$CSI_fg${esc[${val[1]}]}██$gb" \
    "${SC[1]}" "$esc_reset"
  printf "%s      Highlighted background: %-2s%-14s%s%2s    %s\n" \
    "$gb" "${SO[2]}" "${cname[${val[2]}]}" "$CSI_fg${esc[${val[2]}]}██$gb" \
    "${SC[2]}" "$esc_reset"
  printf "%s      Highlighted foreground: %-2s%-14s%s%2s    %s\n" \
    "$gb" "${SO[3]}" "${cname[${val[3]}]}" "$CSI_fg${esc[${val[3]}]}██$gb" \
    "${SC[3]}" "$esc_reset"
}

move_cursor_top() {
  printf "\e[17A\r"
}


while true; do
  print_menu
  # wait for input
  read -rsn1 key
  [[ $key = $'' ]] && break
  [[ $key = $'\u1b' ]] && {
    read -rsn2 key
  }
  [[ -n $key ]] && {
    case "$key" in
      '[D'|h ) val[$selected]=$(((val[selected]+15)%16)) ;;
      '[B'|j ) selected=$((selected >= 3 ? 3 : selected+1)) ;;
      '[A'|k ) selected=$((selected <= 0 ? 0 : selected-1)) ;;
      '[C'|l ) val[$selected]=$(((val[selected]+1) % 16)) ;;
    esac
  }
  move_cursor_top
done

move_cursor_top
selected=5
print_menu

timestamp="$(date +'%Y-%m-%d %H:%M')"

sedscript="/^GRUB_COLOR_NORMAL=/i \# commented out by grub-colour-chooser, $timestamp:
s|^GRUB_COLOR_NORMAL=|\#GRUB_COLOR_NORMAL=|
/^GRUB_COLOR_HIGHLIGHT=/i \# commented out by grub-colour-chooser, $timestamp:
s|^GRUB_COLOR_HIGHLIGHT=|\#GRUB_COLOR_HIGHLIGHT=|
/^GRUB_THEME=/i \# commented out by grub-colour-chooser, $timestamp:
s|^GRUB_THEME=|\#GRUB_THEME=|"

sed "$sedscript" "$etcdefaultgrubfile" > "$tmpfile"
printf "\n#Added by grub-colour-chooser, %s:\nGRUB_COLOR_NORMAL=\"%s\"\nGRUB_COLOR_HIGHLIGHT=\"%s\"\n" \
  "$timestamp" \
  "${cname[${val[1]}]}/${cname[${val[0]}]}" \
  "${cname[${val[3]}]}/${cname[${val[2]}]}"  >> "$tmpfile"

printf "\nThe following changes to %s are proposed:\n\n" "$etcdefaultgrubfile"
diff --color=auto "$etcdefaultgrubfile" "$tmpfile" && true

printf '\e[?25h\n' # unhide cursor and print new line
stty echo
read -p "Apply these changes and run grub-mkconfig [y/N]? " response
if [[ $response =~ ^(yes|y|Y|Yes)$ ]]; then
  sudo cp -- "$tmpfile" "$etcdefaultgrubfile" || exit
  sudo grub-mkconfig -o "$grubconffile"
fi