Fix for unnecessary updates of joysticks and gamepads in GLFW backend

[berke-bakar]

This PR aims to fix issue #2362 . Currently on Update method of each joystick and gamepad we are making a native call to see if the device is still connected (or if it is a gamepad). This fix aims to reduce number of native calls to only necessary ones by using cached results when applicable while employing GLFW's own public partial GlfwCallbacks.JoystickCallback SetJoystickCallback ([PinObject(PinMode.UntilNextCall)] GlfwCallbacks.JoystickCallback callback) to get notified of new connections/disconnections when they happen instead of polling on each Update.

[berke-bakar]

I measured 3 timings:

• window.DoEvents() (input update + glfwPollEvents)
• input update
• enumarate GamePads + Joysticks

Below is a comparison of median timings across 10 runs for 20000 frames:

Measurement	main	this PR	change
window.DoEvents() = glfwPollEvents + input update, us/frame	5.50	2.60	-52.7%
Input update only (GlfwInputContext.ProcessEvents), us/frame	4.89	2.06	-57.8%
Enumerate input.Gamepads + input.Joysticks, us/iter	4.53	0.85	-81.3%

Here is the script i used for time measuring

using System.Diagnostics;
using System.Globalization;
using System.Linq.Expressions;
using System.Reflection;
using Silk.NET.Input;
using Silk.NET.Input.Glfw;
using Silk.NET.Windowing;
using Silk.NET.Windowing.Glfw;

var frames = 5000;
for (var i = 0; i < args.Length; i++)
{
    if (args[i] == "--frames" && i + 1 < args.Length)
    {
        frames = int.Parse(args[++i]);
    }
}

GlfwWindowing.RegisterPlatform();
GlfwInput.RegisterPlatform();

var opts = WindowOptions.Default with { IsVisible = false, Title = "Benchmark", Size = new(320, 240) };
using var window = Window.Create(opts);
window.Initialize();
using var input = window.CreateInput();

var hooked = new HashSet<IInputDevice>();

void SubscribeToInputEvents(IInputDevice d)
{
    if (!hooked.Add(d))
    {
        return;
    }
    switch (d)
    {
        case IGamepad g:
            g.ButtonDown += (gp, b) => Console.WriteLine($"  gamepad[{gp.Index}] {b.Name} down");
            g.ButtonUp += (gp, b) => Console.WriteLine($"  gamepad[{gp.Index}] {b.Name} up");
            break;
        case IJoystick j:
            j.ButtonDown += (js, b) => Console.WriteLine($"  joystick[{js.Index}] button {b.Index} down");
            j.ButtonUp += (js, b) => Console.WriteLine($"  joystick[{js.Index}] button {b.Index} up");
            break;
    }
}

input.ConnectionChanged += (d, connected) =>
{
    Console.WriteLine($"ConnectionChanged: {d.GetType().Name}[{d.Index}] '{d.Name}' {(connected ? "connected" : "disconnected")}");
    if (connected)
    {
        SubscribeToInputEvents(d);
    }
};

var gamepads = input.Gamepads.Count;
var joysticks = input.Joysticks.Count;
Console.WriteLine($"Connected at start: {gamepads} gamepad(s), {joysticks} joystick(s)");

foreach (var g in input.Gamepads)
{
    Console.WriteLine($"-> gamepad[{g.Index}] {g.Name}"); 
    SubscribeToInputEvents(g);
}

foreach (var j in input.Joysticks)
{
    Console.WriteLine($"-> joystick[{j.Index}] {j.Name}"); 
    SubscribeToInputEvents(j);
}

var processEventsMethod = input.GetType().GetMethod("ProcessEvents", BindingFlags.Instance | BindingFlags.Public)!;
var processEvents = Expression.Lambda<Action>(
    Expression.Call(Expression.Constant(input, input.GetType()), processEventsMethod)).Compile();

// Timings
for (var i = 0; i < 500; i++)
{
    // JIT warm up + GLFW joystick subsystem init
    window.DoEvents();
}

var sw = Stopwatch.StartNew();
for (var i = 0; i < frames; i++)
{
    window.DoEvents();
}
var doEventsUs = sw.Elapsed.TotalMicroseconds / frames;

sw.Restart();
for (var i = 0; i < frames; i++)
{
    processEvents();
}
var inputUs = sw.Elapsed.TotalMicroseconds / frames;

sw.Restart();
var n = 0;
for (var i = 0; i < frames; i++)
{
    n += input.Gamepads.Count() + input.Joysticks.Count();
}
var enumUs = sw.Elapsed.TotalMicroseconds / frames;

Console.WriteLine($"{frames} frames:");
Console.WriteLine($"-> DoEvents (glfwPollEvents + input update): {doEventsUs:F2} us/frame");
Console.WriteLine($"-> input update only:                        {inputUs:F2} us/frame");
Console.WriteLine($"-> enumerate Gamepads + Joysticks:           {enumUs:F2} us/iter (n={n})");

// // Second context, register/unregister of the shared joystick callback with two live contexts.
// using (var window2 = Window.Create(opts with { Title = "Benchmark2" }))
// {
//     window2.Initialize();
//     using var input2 = window2.CreateInput();
//     for (var i = 0; i < 10; i++)
//     {
//         window2.DoEvents();
//         window.DoEvents();
//     }
//     Console.WriteLine($"Second input context OK ({input2.Gamepads.Count} gamepad(s), {input2.Joysticks.Count} joystick(s))");
// }
//
// for (var i = 0; i < 10; i++)
// {
//     window.DoEvents();
// }
// Console.WriteLine("Second context disposed, first context still updating OK");

Machine info:

• 13th Gen Intel(R) Core(TM) i9-13900K
• Windows build 10.0.26200.0
• .NET SDK 8.0.418

[berke-bakar]

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