#!/bin/bash

#
# 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
# Remove opacity property of current window
#   $ compton-trans -c none

if test -z "$(which xprop)" -o -z "$(which xwininfo)"; then
  echo "Please install x11-utils/xorg-xprop/xorg-xwininfo." >& 2
  exit 1
fi

window=
opacity=
cur=
root=
parent=
i=

#
# Options
#

arg=
val=
active=
select=

while test $# -gt 0; do
  arg="$1"
  shift
  case "$arg" in
    -s | -select | --select) ;;
    -c | -current | --current)
      active=$(xprop -root -notype "_NET_ACTIVE_WINDOW" \
        | sed 's/^.*\(0x\S*\).*$/\1/')
      window="-id $active"
    ;;
    -n | -name | --name)
      val="$1"
      shift
      window="-name $val"
    ;;
    -w | -window | --window)
      val="$1"
      shift
      window="-id $val"
    ;;
    -o | -opacity | --opacity)
      val="$1"
      shift
      opacity="$val"
    ;;
    *)
      opacity="$arg"
    ;;
  esac
done

if test -z "$window"; then
  select=$(xwininfo | grep 'Window id:' | sed 's/^.*\(0x\S*\).*$/\1/')
  window="-id $select"
fi

#
# Find Window
#

root=$(xwininfo -all -root \
  | grep "Root window id" \
  | sed 's/^.*\(0x\S*\).*$/\1/')

parent=$window
i=0

while true; do
  parent=$(xwininfo -all $parent \
    | grep Parent \
    | sed 's/^.*\(0x\S*\).*$/\1/')

  if test -z "$parent"; then
    echo "Window not found." >& 2
    exit 1
  fi

  if test "$parent" = "$root"; then
    break
  fi

  parent="-id $parent"
  window=$parent

  i=$((i + 1))
  if test $i -ge 1000; then
    echo "An error occurred while traversing up the window tree." >& 2
    echo "Please report this to https://github.com/chjj/compton/issues." >& 2
    echo "Please mention your WM and versions of xwininfo/xprop." >& 2
    exit 1
  fi
done

if test -z "$window"; then
  echo "Window not found." >& 2
  exit 1
fi

#
# Check (or Delete) Opacity
#

if test "$opacity" = "none"; then
  xprop $window -remove _NET_WM_WINDOW_OPACITY
  exit $?
fi

opacity=$(echo "$opacity" | sed 's/[^-+0-9]//g')
if test -z "$opacity"; then
  echo "Bad opacity value." >& 2
  exit 1
fi

#
# Determine Relative Opacity
#

if test -n "$(echo "$opacity" | sed 's/^\(+\|-\).*$\|^.*$/\1/')"; then
  cur=$(xprop $window -notype "_NET_WM_WINDOW_OPACITY" \
    | sed 's/^.*\b\([0-9]\+\).*$\|^.*$/\1/')
  test -z "$cur" && cur=$((0xffffffff))
  cur=$((cur * 100 / 0xffffffff))
  opacity=$((cur + opacity))
fi

#
# Determine and Set Opacity
#

if test -n "$opacity" -a -n "$window"; then
  test $opacity -lt 0 && opacity=0
  test $opacity -gt 100 && opacity=100
  opacity=$((opacity * 0xffffffff / 100))
  xprop $window -f _NET_WM_WINDOW_OPACITY 32c \
    -set _NET_WM_WINDOW_OPACITY "$opacity"
fi