BTN_STYLUS3 has been introduced by the Linux 4.15 kernel to report the
status of the third button present on Wacom's new "Pro Pen 3D" stylus.
Treat this button like xf86-input-wacom and send a button 8 event
("navigate back") when received from Wayland.
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
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