gifbg.sh

#!/bin/sh
#
# Uses animated files as wallpapers.
# Requires: mpv(1) and convert(1)

set -e

: "${_ext=gif}"

__usage () {
  cat << EOH
$0 path
$0 -h

$0 will use animated files in "path" and use them as looping wallpapers
$0 -h displays this help text

We look for files ending in $_ext .
You might set \$_ext to change this behavior.
Use SIGUSR1 to use another random wallpaper (might be the same!)
Use SIGUSR2 to generate the file list again
EOH
}

# parsing options
case "$1" in
  -h|help) __usage ; exit 0 ;;
  "") __usage >&2  ; exit 1 ;;
  *) _path="$1" ;;
esac

# simple, stupid check
ls "$_path" >/dev/null

# We work in a temporary dir
_tmp="$(mktemp -dt "$(basename "$0").XXXX")"

__cleanup () {
  [ -d "$_tmp" ] && rm -rf "${_tmp:?}"
}

trap __cleanup INT TERM

__create_list () {
  # We list the files and store that have the good extension
  : > "$_tmp/list"
  for _e in $_ext; do
    find "$_path" -name '*.'$_e >> "$_tmp/list"
  done
}

__create_list

trap __create_list USR2

__pick_one () {
  # We randomly pick one file and return its path
  shuf "$_tmp/list" | head -n 1
}

__bg () {
  # Select bg color:
  # convert(1) to extract the single top-left pixel and extract its color
  # throughout the .gif; then grep for its only values that are NOT transparent
  # and then take the first one
  _solid_color="$(convert "$1" -crop 1x1+0+0 -depth 8 txt: | grep -Eo \
    '#[A-F0-9]{6}(FF|)' | sort -u | head -n 1)"

  # Now $_solid_color contains either #RRGGBB or #RRGGBBAA and we need to
  # discard the 'AA' part (where AA = FF anyway, because we used grep earlier),
  # hence the '%%FF'
  _solid_color="${_solid_color%%FF}"

  printf '%s\n' "${_solid_color}"
}

__run_mpv () {
  mpv --border --video-unscaled --background="$2" --wid=0 "$1" --loop-file=inf --speed=1.0 >/dev/null 2>&1 &
  #sxiv -b -e 0 -Z -a $1
}

__kill () {
  kill "$(pgrep -P "$$" "$1")" 2>/dev/null || :
}

__set_a_wp () {
  _gif="$(__pick_one)"
  _bg="$(__bg "$_gif")"
  __kill mpv
  __run_mpv "$_gif" "$_bg"
}

__set_a_wp

trap __set_a_wp USR1
trap '__kill mpv; __cleanup' INT TERM

mkfifo "$_tmp/fifo" || exit
chmod 600 "$_tmp/fifo"
read < "$_tmp/fifo" 2>/dev/null

__cleanup