AvaloniaKeyboardAdapter.cs

using System.Runtime.CompilerServices;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Input;
using Avalonia.Interactivity;
using Gondwana.Input.Keyboard;
using Microsoft.Extensions.Logging;
 
namespace Gondwana.Avalonia.Input.Keyboard;

public sealed class AvaloniaKeyboardAdapter : IKeyboardAdapter, IDisposable
{
    public static int? GetKeyCodeFromString(string keyName)
    {
        if (Enum.TryParse<Key>(keyName, true, out var key))
            return (int)key;
 
        Engine.Logger.LogWarning("Invalid Avalonia key name: {KeyName}", keyName);
        return null;
    }
 
    private readonly Control _lifetimeOwner;
    private TopLevel? _topLevel;
 
    // Key state table indexed by (int)Key
    private readonly int[] _down = new int[512];
 
    // Modifier bits published lock-free
    private int _modsBits;
 
    private bool _isDisposed;

    public KeyboardModifierState CurrentKeyboardModifiers =>
        (KeyboardModifierState)Volatile.Read(ref _modsBits);

    public AvaloniaKeyboardAdapter(Control lifetimeOwner)
    {
        _lifetimeOwner = lifetimeOwner ?? throw new ArgumentNullException(nameof(lifetimeOwner));
 
        _lifetimeOwner.AttachedToVisualTree += OnAttachedToVisualTree;
        _lifetimeOwner.DetachedFromVisualTree += OnDetachedFromVisualTree;
 
        // If the control is already part of the visual tree, connect immediately
        if (TopLevel.GetTopLevel(_lifetimeOwner) != null)
            ConnectToTopLevel();
 
        Engine.Logger.LogInformation("AvaloniaKeyboardAdapter initialized.");
    }
 
    private void OnAttachedToVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
        => ConnectToTopLevel();
 
    private void OnDetachedFromVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
        => DisconnectFromTopLevel();
 
    private void ConnectToTopLevel()
    {
        if (_isDisposed) return;
 
        var tl = TopLevel.GetTopLevel(_lifetimeOwner);
        if (tl == null || ReferenceEquals(tl, _topLevel)) return;
 
        _topLevel = tl;
        tl.AddHandler(InputElement.KeyDownEvent, OnKeyDown, RoutingStrategies.Tunnel);
        tl.AddHandler(InputElement.KeyUpEvent, OnKeyUp, RoutingStrategies.Tunnel);
    }
 
    private void DisconnectFromTopLevel()
    {
        if (_topLevel == null) return;
 
        _topLevel.RemoveHandler(InputElement.KeyDownEvent, OnKeyDown);
        _topLevel.RemoveHandler(InputElement.KeyUpEvent, OnKeyUp);
        _topLevel = null;
    }
 
    private void OnKeyDown(object? sender, KeyEventArgs e)
    {
        if (_isDisposed) return;
        SetDown((int)e.Key, true);
        UpdateMods(e.KeyModifiers);
    }
 
    private void OnKeyUp(object? sender, KeyEventArgs e)
    {
        if (_isDisposed) return;
        SetDown((int)e.Key, false);
        UpdateMods(e.KeyModifiers);
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public bool IsDown(int keyCode)
    {
        if ((uint)keyCode >= (uint)_down.Length) return false;
        return Volatile.Read(ref _down[keyCode]) != 0;
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private void SetDown(int keyCode, bool down)
    {
        if ((uint)keyCode >= (uint)_down.Length) return;
        Volatile.Write(ref _down[keyCode], down ? 1 : 0);
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private void UpdateMods(KeyModifiers km)
    {
        int mods = 0;
        if ((km & KeyModifiers.Shift) != 0) mods |= (int)KeyboardModifierState.Shift;
        if ((km & KeyModifiers.Control) != 0) mods |= (int)KeyboardModifierState.Ctrl;
        if ((km & KeyModifiers.Alt) != 0) mods |= (int)KeyboardModifierState.Alt;
        Volatile.Write(ref _modsBits, mods);
    }

    public void Dispose()
    {
        if (_isDisposed) return;
 
        _isDisposed = true;
 
        DisconnectFromTopLevel();
        _lifetimeOwner.AttachedToVisualTree -= OnAttachedToVisualTree;
        _lifetimeOwner.DetachedFromVisualTree -= OnDetachedFromVisualTree;
 
        Engine.Logger.LogInformation("AvaloniaKeyboardAdapter disposed.");
    }
}