AvaloniaMouseAdapter.cs

using System.Drawing;
using Avalonia.Controls;
using Avalonia.Input;
using Gondwana.Input.Keyboard;
using Gondwana.Input.Mouse;
using GondwanaMouseButton = Gondwana.Input.Mouse.MouseButton;
 
namespace Gondwana.Avalonia.Input.Mouse;

public sealed class AvaloniaMouseAdapter : IMouseAdapter, IDisposable
{
    private readonly Control _control;
    private readonly HashSet<GondwanaMouseButton> _pressed = new();
    private PointF _currentPosition;
    private KeyboardModifierState _modifiers;
    private int _scrollDelta;

    public Point CurrentPosition => PointerCoordinates.ToScreenPx(_control, _currentPosition);

    public HashSet<GondwanaMouseButton> PressedButtons => _pressed;

    public KeyboardModifierState CurrentKeyboardModifiers => _modifiers;

    public int ScrollDelta => Interlocked.Exchange(ref _scrollDelta, 0);

    public AvaloniaMouseAdapter(Control control)
    {
        _control = control ?? throw new ArgumentNullException(nameof(control));
 
        _control.PointerPressed += OnPointerPressed;
        _control.PointerReleased += OnPointerReleased;
        _control.PointerMoved += OnPointerMoved;
        _control.PointerWheelChanged += OnPointerWheelChanged;
    }
 
    private void OnPointerPressed(object? sender, PointerPressedEventArgs e)
    {
        var point = e.GetCurrentPoint(sender as Control);
        _pressed.Add(MapButton(point.Properties));
        UpdatePosition(e, sender as Control);
    }
 
    private void OnPointerReleased(object? sender, PointerReleasedEventArgs e)
    {
        _pressed.Remove(MapReleasedButton(e.InitialPressMouseButton));
        UpdatePosition(e, sender as Control);
    }
 
    private void OnPointerMoved(object? sender, PointerEventArgs e)
    {
        UpdatePosition(e, sender as Control);
    }
 
    private void UpdatePosition(PointerEventArgs e, Control? relativeTo)
    {
        var pos = e.GetPosition(relativeTo);
        _currentPosition = new PointF((float)pos.X, (float)pos.Y);
 
        _modifiers = KeyboardModifierState.None;
        var km = e.KeyModifiers;
        if ((km & KeyModifiers.Shift) != 0) _modifiers |= KeyboardModifierState.Shift;
        if ((km & KeyModifiers.Control) != 0) _modifiers |= KeyboardModifierState.Ctrl;
        if ((km & KeyModifiers.Alt) != 0) _modifiers |= KeyboardModifierState.Alt;
    }
 
    private static GondwanaMouseButton MapButton(PointerPointProperties props)
    {
        if (props.IsLeftButtonPressed) return GondwanaMouseButton.Left;
        if (props.IsRightButtonPressed) return GondwanaMouseButton.Right;
        if (props.IsMiddleButtonPressed) return GondwanaMouseButton.Middle;
        return GondwanaMouseButton.None;
    }
 
    private static GondwanaMouseButton MapReleasedButton(global::Avalonia.Input.MouseButton initialPressButton) => initialPressButton switch
    {
        global::Avalonia.Input.MouseButton.Left => GondwanaMouseButton.Left,
        global::Avalonia.Input.MouseButton.Right => GondwanaMouseButton.Right,
        global::Avalonia.Input.MouseButton.Middle => GondwanaMouseButton.Middle,
        _ => GondwanaMouseButton.None
    };
 
    private void OnPointerWheelChanged(object? sender, PointerWheelEventArgs e)
    {
        // Avalonia Delta.Y is in lines; positive = scroll up (matches WinForms convention).
        // Multiply by 120 to approximate Windows WHEEL_DELTA units for compatibility.
        var delta = (int)(e.Delta.Y * 120);
        Interlocked.Add(ref _scrollDelta, delta);
    }

    public void Dispose()
    {
        _control.PointerPressed -= OnPointerPressed;
        _control.PointerReleased -= OnPointerReleased;
        _control.PointerMoved -= OnPointerMoved;
        _control.PointerWheelChanged -= OnPointerWheelChanged;
    }
}