Xorg initrc configuration.

.xinitrc

#!/bin/sh
#
# ~/.xinitrc
#
# Executed by startx (run your window manager from here)

if [ -d /etc/X11/xinit/xinitrc.d ]; then
  for f in /etc/X11/xinit/xinitrc.d/*; do
    [ -x "$f" ] && . "$f"
  done
  unset f
fi

# CUSTOM, trusktr
# Enable natural scrolling (i.e. swap scrolling directions)
xinput set-button-map "SynPS/2 Synaptics TouchPad" 1 2 3 5 4 7 6
# TODO: do this in system-wide configuration instead.
# END CUSTOM

# exec gnome-session
# exec startkde
# exec startxfce4
# ...or the Window Manager of your choice