Wacom Tablet to Window Mapping

setinput.sh

#!/bin/bash

# Map the tablet to cover a particular window, while maintaining its aspect
# ratio.  If run from the terminal, it allows the user to click on the window
# for mapping.  Otherwise, use the currently focused window.  Should the
# window aspect ratio not match the tablet aspect ratio, the tablet will
# cover an additional area of the screen, to maintain the correct aspect
# ratio.  By default, the window will be aligned with the top-left corner
# of the tablet, but options adjust the horizontal (-l, -c, -r) and vertical
# (-t, -m, -b) alignment.
#
# Note that for decorated windows, the window area does not include the
# title bar.  For undecorated windows, the window area may extent beyond
# the visible area, to include any shadow effects.
#
# It can be handy to hook this script up to one of the buttons on the tablet.
# In GNOME, I did this by setting a system-wide shortcut to run the script,
# and then connected the left tablet button to that shortcut.  Since the
# script isn't running in a terminal, it immediately sets the tablet to map
# to the current active window.

# If you have a different tablet, you may need to adjust the name.  Run
# `xsetwacom --list devices` to see what yours is.
TABLET="Wacom Intuos S Pen stylus"
XWI_ARGS=""
if [[ ! -t 0 ]]; then
  XWI_ARGS="-id $(xprop -root 32x '\t$0' _NET_ACTIVE_WINDOW | cut -f 2)"
fi

# Default is to map the upper-left corner of the tablet to the upper-left
# corner of the window.  This makes sense, at least for right-handers, since
# it gives you more of the tablet under your hand.  I originally thought
# centering would make more sense, but experience suggests otherwise.
xf=0
yf=0

while getopts ":tmblcr" opt; do
  case ${opt} in
    t)
      yf=0
      ;;
    m)
      yf=1
      ;;
    b)
      yf=2
      ;;
    l)
      xf=0
      ;;
    c)
      xf=1
      ;;
    r)
      xf=2
      ;;
    \?)
      echo "Alignment options:"
      echo "  -t  Top"
      echo "  -m  Middle"
      echo "  -b  Bottom"
      echo "  -l  Left"
      echo "  -c  Center"
      echo "  -r  Right"
      exit 1
      ;;
  esac
done
shift $((OPTIND - 1))

# https://unix.stackexchange.com/a/14170

# Get the coordinates of the active window's
#    top-left corner, and the window's size.
#    This excludes the window decoration.
read -d '' wx wy ww wh <<<$(xwininfo $XWI_ARGS |
  sed -n -e "s/^ \+Absolute upper-left X: \+\(-\?[0-9]\+\).*/\1/p" \
         -e "s/^ \+Absolute upper-left Y: \+\(-\?[0-9]\+\).*/\1/p" \
         -e "s/^ \+Width: \+\([0-9]\+\).*/\1/p" \
         -e "s/^ \+Height: \+\([0-9]\+\).*/\1/p" )

read -r tx ty tw th <<<$(xsetwacom --get "$TABLET" Area)

war=$(bc -l <<<$(echo "$ww / $wh" ))
tar=$(bc -l <<<$(echo "$tw / $th" ))
if (( $(bc <<<$(echo "$war > $tar")) )); then
  # Window is wider than tablet.  Tablet should be mapped to greater height than window
  mw=$ww
  mh=$(bc <<<$(echo "$wh * $war / $tar" ))
  mx=$wx
  my=$(( $wy - ($mh - $wh) * $yf / 2 ))
else
  # Tablet is wider than window.  Tablet should be mapped to greater width than window
  mw=$(bc <<<$(echo "$ww * $tar / $war" ))
  mh=$wh
  mx=$(( $wx - ($mw - $ww) * $xf / 2 ))
  my=$wy
fi

set -x
xsetwacom --set "$TABLET" MapToOutput "${mw}x${mh}+${mx}+${my}"