Fix linux segfault when no display

[danjcjones]

This fixes a segmentation fault when there is no display, i.e. running CLI. As soon as the mouse is moved, it tries to fetch the current mouse position, but errors as no display. This returns a position of -1, -1, to indicate this, and to allow it to continue triggering button events.

Fixes issue #65 and mentioned in #77.

Tested on Raspbian GNU/Linux 10 (buster)

[july12123]

(works for me on Raspian CLI ) if people need this version uninstall Mouse Module and do
sudo pip3 install git+https://github.com/danjcjones/mouse.git

[guynich]

sudo pip3 install git+https://github.com/danjcjones/mouse.git

This worked for me on Ubuntu Server 22.04.2 LTS (Jammy Jellyfish) - specifically to mitigate a segmentation fault when moving a physical USB mouse that is connected to a single board computer.

[groupmsl]

This fixed the authorisation error mentioned above for me too. I'm not using SSH, but Wayland (Sway to be specific).

Any chance this could be merged?

[dovedevic]

Is it possible to get mouse deltas (not absolute x/y positions) while in a headless linux environment instead of just -1 -1 x/y positions?