make flatpak packages for Linux

[sthalik]

Making flatpak packages is easier than Debian boilerplate.

Running continuous integration on Linux will help with compile-testing at the very least. Maybe even some very simple unit tests with offscreen rendering.

[sthalik]

Actually opentrack needs access to the global system due to Wine integration, etc.

[jwmullally]

Here's a simple Flatpak build for OpenTrack: com.github.opentrack.test.json. I've seen a few people ask for one.

It works well with the neuralnet camera input and libevdev Joystick and UDP Network outputs. It would be good to package something like this up on Flathub even with limited inputs/outputs, especially for container only OS's like Fedora Silverblue, Endless OS, Elementary OS, etc.

Building:

flatpak-builder --user --install --force-clean ../com.github.opentrack.test.build com.github.opentrack.test.json

Running:

sudo modprobe uinput
sudo chgrp wheel /dev/uinput
flatpak run com.github.opentrack.test

With --socket=wayland, the "Options" window crashes, so I left it out and it works fine with X11 fallback.

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You can use jstest-gtk to see the all 6 output axes (and 1 button).

It works OK with DCS under Flatpak Steam (but for me at least is a bit jumpy/jaggy). With Steam Input disabled, it shows up as an "opentrack headpose" joystick with 5 assignable axes that all work (Wine maps both Roll and Pitch to the same Z axis so I could only use one at a time by disabling the other output in OpenTrack).

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Test:
All seperate flatpaks.
Input: neuralnet tracker
USB Webcam: 640x480 10fps (I can't seem to change the FPS...)
Neuralnet Inference time: <5ms with 2 threads
Output: libevdev joystick receiver
Joystick shows as /dev/input/js0 opentrack headpose

OpenTrack Output	jstest-gtk	Bottles Wine control.exe Joystick
X	Axis 0	X
Y	Axis 1	Y
Z	Axis 2	RX
Yaw	Axis 3	RY
Pitch	Axis 4	Z
Roll	Axis 5	Z

Problem: Pitch and Roll show as seperate axes 4 and 5 in jstest-gtk, but both get mapped to the same Z axis under Wine. Clearly seen by enabling each output one-by-one.

[jwmullally]

@sthalik : You could re-open this issue here if there is interest in this. It would need a few adjustments to add to Flathub.

[karuoxa]

I did a quick test of the flatpak example made by @jwmullally yesterday and it it worked very well during my test.
It was however limited to PointTracker/Evdev Virtual Joystick for use with the game War Thunder on Arch.

It would be amazing to see an official flatpak of Opentrack.