BTN_STYLUS3 is defined by the Linux 4.15 kernel and is sent when the third button on a stylus is pressed. At the moment, only Wacom's "Pro Pen 3D" has three stylus buttons. Pressing this button triggers a button 8 event to be sent under X11, so we use the same mapping here.
6fd6ff2ea1 wayland: Add support for BTN_STYLUS3
gdk/wayland/gdkdevice-wayland.c | 6 ++++++
1 file changed, 6 insertions(+)