#!/bin/sh

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

# Usage:
# 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

window=
opacity=
cur=
i=

# Read options
while getopts "scn: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"
    ;;
    n) wprefix='-name '; window="$OPTARG" ;;
    w) wprefix='-id '; window="$OPTARG" ;;
    o) opacity="$OPTARG" ;;
    \?) exit 1;;
  esac
done

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

# Validate opacity value
if [ -z "$opacity" ]; then
  echo "No opacity specified."
  exit 1
fi

opacity="$(echo "$opacity" \
  | sed -rn 's/^[[:space:]]*([+-]?[[:digit:]]+)[[:space:]]*$/\1/p')"

if [ -z "$opacity" ]; then
  echo "Invalid opacity value."
  exit 1
fi

# Get ID of the target window
if [ -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 [ -z "$wid" ]; then
  echo "Failed to find window."
  exit 1
fi

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

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

  if [ -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 [ -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 -n1)
fi

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

# Calculate the desired opacity
if echo "$opacity" | grep '^[+-]' > /dev/null; then
  sign=$(echo "$opacity" | cut -b1)
  cur=$(xprop -id "$topmost" -notype "_NET_WM_WINDOW_OPACITY" \
    | sed 's/^.*\b\([0-9]\+\).*$\|^.*$/\1/')
  [ -z "$cur" ] && cur=0xffffffff
  cur=$((cur * 100 / 0xffffffff))
  opacity="$(echo "$opacity" | sed 's/^[+-]//')"
    opacity=$(($cur $sign $opacity))
fi

[ $opacity -lt 0 ] && opacity=0
[ $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"