Nfw.Linux.Joystick

A Joystick/Gamepad Library with generic support for the Linux input system and the /dev/input/js device(s). Original inspiration from https://github.com/nahueltaibo/gamepad - many thanks and attribution due to that repo and its original parsing code.

This library extends and goes beyond however, providing 3 layers with which you can interact with controllers:

• Simple: You tell the library what /dev/input/js to read, and provide a callback for Button and Axis events
• Smart: Builds on Simple and let's you subscribe to specific events, including synthetic things like "ShortPress" vs "LongPress" (see full list here: https://github.com/nate-yocom/Nfw.Linux.Joystick/blob/main/lib/Smart/ButtonEventTypes.cs)
• Xpad: Builds on Smart layer, with direct mapping for supporting XBox controllers (as supported by the Linux xpad driver), as well as support for mapping Axis events to buttons (i.e. a Button event for DPadLeft vs DPadRight)

All Layers

• Providing a Microsoft.Extensions.Logging.ILogger (perhaps via IoC) at construction time
• Retrieving the name of the attached device (as provided by the manufacturer/device in response to an ioctl)
• Callback on connect/disconnect (and no events when disconnected)
• Current connected state available via the Connected property
• Current device being watched via the Device property

NuGet

dotnet add package Nfw.Linux.Joystick

Samples

See samples for each layer: https://github.com/nate-yocom/Nfw.Linux.Joystick/tree/main/samples

Simple Layer

This layer is, as the name suggests, the simplest, with no real configuration beyond providing the path to the device file to read from (and watch for connect/disconnect):

using Nfw.Linux.Joystick.Simple;

using(Joystick joystick = new Joystick("/dev/input/js0")) {
    joystick.ButtonCallback = (j, button, pressed) => {
        Console.WriteLine($"{j.DeviceName} => Button[{button}] => {pressed}");
    };

    joystick.AxisCallback = (j, axis, value) => {
        Console.WriteLine($"{j.DeviceName} => Axis[{axis}] => {value}");
    };

    joystick.ConnectedCallback = (j, c) => {
        Console.WriteLine($"{j.DeviceName} => Connected[{c}]");
    };

    Console.WriteLine("Watching for js0 events, press enter to quit...");
    Console.ReadLine();
}

Smart Layer

This layer adds the ability to report events with more meaning - i.e. Short vs Long press (avoiding the need for the library user to do timing and state tracking). This also introduces a per-axis or button elapsed time since last event argument to the callback, allowing for custom timing logic in user code.

using Nfw.Linux.Joystick.Smart;

using(Joystick joystick = new Joystick("/dev/input/js0", ButtonEventTypes.All)) {

    // We can optionally set the behavior controller wide, or per button, re what constitutes a LongPress vs a ShortPress:
    //  To do this per-button, call joystick.SetButtonSettings(<button id>, <settings>);    
    joystick.DefaultButtonSettings = new ButtonSettings() { 
        LongPressMinimumDurationMilliseconds = 500
    };

    joystick.ButtonCallback = (j, button, eventType, pressed, elapsedTime) => {
        Console.WriteLine($"{j.DeviceName} => Button[{button}] => {eventType} [Current: {pressed} Elapsed: {elapsedTime}]");
    };

    joystick.AxisCallback = (j, axis, value, elapsedTime) => {
        Console.WriteLine($"{j.DeviceName} => Axis[{axis}] => {value} [Elapsed: {elapsedTime}]");
    };

    joystick.ConnectedCallback = (j, c) => {
        Console.WriteLine($"{j.DeviceName} => Connected[{c}]");
    };

    Console.WriteLine("Watching for js0 events, press enter to quit...");
    Console.ReadLine();
}

Note that the second argument to this constructor allows for masking in/out specific events as desired.

Xpad Layer

This layer is idea for the case where you know the attached controller is an XBox controller - as supported by the Xpad driver for Linux. Optionally, calling code can also ask that all Axis be mapped as button events.

using Nfw.Linux.Joystick.Smart;
using Nfw.Linux.Joystick.Xpad;

using(XboxGamepad joystick = new XboxGamepad("/dev/input/js0", ButtonEventTypes.All)) {
    // We can optionally set the behavior controller wide, or per button, re what constitutes a LongPress vs a ShortPress:
    //  To do this per-button, call joystick.SetButtonSettings(<button id>, <settings>);    
    joystick.DefaultButtonSettings = new ButtonSettings() { 
        LongPressMinimumDurationMilliseconds = 500
    };

    // We can optionally turn all axis events into buttons if we want:
    //      joystick.TreatAxisAsButtons = true;
    //
    // When mapping to buttons, we can:
    //
    //      Adjust the deadzone (center) for axis as a distance from 0 with:
    //          joystick.MappedAxisButtonCenterForgiveness = 1024;
    //
    //      Adjust the % of max which constitutes a button press when mapping an axis to a button    
    //          joystick.MappedAxisButtonPressThreshold = 0.90f;

    joystick.ButtonCallback = (j, button, eventType, pressed, elapsedTime) => {
        Console.WriteLine($"{j.DeviceName} => Button[{button}] => {eventType} [Current: {pressed} Elapsed: {elapsedTime}]");
    };

    joystick.AxisCallback = (j, axis, value, elapsedTime) => {
        Console.WriteLine($"{j.DeviceName} => Axis[{axis}] => {value} [Elapsed: {elapsedTime}]");
    };

    joystick.ConnectedCallback = (j, c) => {
        Console.WriteLine($"{j.DeviceName} => Connected[{c}]");
    };

    Console.WriteLine("Watching for js0 events, press enter to quit...");
    Console.ReadLine();
}

Note that this layer also includes support for the Profile button specific to the Microsoft X-Box Adaptive Controller, which requires a newer Xpad driver than currently in any mainline Linux tree. See https://github.com/nate-yocom/xpad-xac for such a driver.

References

• Gamepad library: https://github.com/nahueltaibo/gamepad by @nahueltaibo
• Linux kernel joystick API: https://www.kernel.org/doc/Documentation/input/joystick-api.txt

Changes

• 1.0.4 moves found controller message in log to Trace from Information
• 1.0.3 adds static device probe helper to Joystick class
• 1.0.2 adds autoprobe on construction for device name
• 1.0.1 fixes device access to be non-exclusive and read only