#!/bin/sh

#
# compton-trans
# transset in a bash script
# Copyright (c) 2011-2012, Christopher Jeffrey
#

# Usage:
#  $ compton-trans [options] [+|-]opacity
# By window id
#   $ compton-trans -w "$WINDOWID" 75
# By name
#   $ compton-trans -n "urxvt" 75
# By current window
#   $ compton-trans -c 75
# By selection
#   $ compton-trans 75
#   $ compton-trans -s 75
# Increment current window 5%
#   $ compton-trans -c +5

# "command" is a shell built-in, faster than "which"
if test -z "$(command -v xprop)" -o -z "$(command -v xwininfo)"; then
  echo 'Please install x11-utils/xorg-xprop/xorg-xwininfo.' >& 2
  exit 1
fi

# Variables
active=
wprefix=
window=
opacity=
cur=
action=
treeout=
wid=
topmost=
lineno=

# This takes into account the fact that getopts stops on
# any argument it doesn't recongize or errors on. This
# allows for things like `compton-trans -5` as well
# as `compton-trans -c +5 -s` (contrived example).
while test $# -gt 0; do
  # Reset option index
  OPTIND=1
  LASTIND=1

  # Read options
  while getopts ':scdgn:w:o:' option "$@"; do
    case "$option" in
      s) wprefix=''; window='' ;;
      c)
        active=$(xprop -root -notype _NET_ACTIVE_WINDOW \
          | sed 's/^.*\(0x\S*\).*$/\1/')
        wprefix='-id'; window=$active
      ;;
      d) action='delete' ;;
      g) action='get' ;;
      n) wprefix='-name'; window=$OPTARG ;;
      w) wprefix='-id'; window=$OPTARG ;;
      o) opacity=$OPTARG ;;
      \?)
        # For some reason single char options `-x` stop on the OPTIND after the
        # argument index, whereas two or more character options (`-foo`) stop
        # on the argument's index, so we use LASTIND here instead. If OPTIND is
        # not equal to LASTIND, this means -x was used instead of -xx.
        OPTIND=$LASTIND
        break
      ;;
    esac
    LASTIND=$OPTIND
  done

  # Read positional arguments
  shift $((OPTIND - 1))
  test -n "$1" && opacity=$1 && shift
done

# clean up opacity. xargs == a poor man's trim.
opacity=$(echo "$opacity" | sed 's/%//g' | xargs)

# Validate opacity value
if test -z "$action" && ! echo "$opacity" | grep -q '^[+-]\?[0-9]\+$'; then
  echo "Invalid opacity specified: $opacity."
  exit 1
fi

# Get ID of the target window
if test -z "$wprefix"; then
  treeout=$(xwininfo -children -frame)
else
  treeout=$(xwininfo -children $wprefix "$window")
fi

wid=$(echo "$treeout" | sed -n 's/^xwininfo:.*: \(0x[[:xdigit:]]*\).*$/\1/p')

if test -z "$wid"; then
  echo 'Failed to find window.'
  exit 1
fi

# Make sure it's not root window
if echo "$treeout" | fgrep -q 'Parent window id: 0x0'; then
  echo 'Cannot set opacity on root window.'
  exit 1
fi

# If it's already the topmost window
if echo "$treeout" | grep -q 'Parent window id: 0x[[:xdigit:]]* (the root window)'; then
  topmost=$wid
else
  # Get the whole window tree
  treeout=$(xwininfo -root -tree)

  if test -z "$treeout"; then
    echo 'Failed to get root window tree.'
    exit 1
  fi

  # Find the line number of the target window in the window tree
  lineno=$(echo -n "$treeout" | grep -nw "$wid" | head -n1 | cut -d ':' -f 1)

  if test -z "$lineno"; then
    echo 'Failed to find window in window tree.'
    exit 1
  fi

  # Find the highest ancestor of the target window below
  topmost=$(echo -n "$treeout" \
    | head -n $(($lineno + 1)) \
    | sed -n 's/^     \(0x[[:xdigit:]]*\).*/\1/p' \
    | tail -n 1)
fi

if test -z "$topmost"; then
  echo 'Failed to find the highest parent window below root of the' \
    'selected window.'
  exit 1
fi

# Remove the opacity property.
if test x"$action" = x'delete'; then
  xprop -id "$topmost" -remove _NET_WM_WINDOW_OPACITY
  exit 0
fi

# Get current opacity.
cur=$(xprop -id "$topmost" -notype _NET_WM_WINDOW_OPACITY \
  | sed 's/^.*\b\([0-9]\+\).*$\|^.*$/\1/')
test -z "$cur" && cur=0xffffffff
cur=$((cur * 100 / 0xffffffff))

# Output current opacity.
if test x"$action" = x'get'; then
  echo "$cur"
  exit 0
fi

# Calculate the desired opacity
if echo "$opacity" | grep -q '^[+-]'; then
  opacity=$(($cur + $opacity))
fi

test $opacity -lt 0 && opacity=0
test $opacity -gt 100 && opacity=100

# Set opacity
opacity=$((opacity * 0xffffffff / 100))
xprop -id "$topmost" -f _NET_WM_WINDOW_OPACITY 32c \
  -set _NET_WM_WINDOW_OPACITY "$opacity"