Debian 9 + Xfce + TouchPad

apt-get install xserver-xorg-input-synaptics

/usr/share/X11/xorg.conf.d/70-synaptics.conf

/etc/X11/xorg.conf.d/70-synaptics.conf
Section "InputClass"
    Identifier "touchpad catchall"
    Driver "synaptics"
    MatchIsTouchpad "on"
        Option "TapButton1" "1"
        Option "TapButton2" "3"
        Option "TapButton3" "2"
EndSection