BlazorLogicalResolutionBinding.cs

using Gondwana.Rendering;
 
namespace Gondwana.Blazor.Hosting;

internal sealed class BlazorLogicalResolutionBinding : IDisposable
{
    private readonly RenderSurfaceAdapterBase _adapter;
    private readonly Action<float> _applyScale;
    private readonly int _logicalWidth;
    private readonly int _logicalHeight;
    private bool _established;
    private bool _disposed;

    internal BlazorLogicalResolutionBinding(
        RenderSurfaceAdapterBase adapter,
        int logicalWidth,
        int logicalHeight,
        Action<float> applyScale)
    {
        ArgumentNullException.ThrowIfNull(adapter);
        ArgumentNullException.ThrowIfNull(applyScale);
        ArgumentOutOfRangeException.ThrowIfNegativeOrZero(logicalWidth);
        ArgumentOutOfRangeException.ThrowIfNegativeOrZero(logicalHeight);
 
        _adapter = adapter;
        _logicalWidth = logicalWidth;
        _logicalHeight = logicalHeight;
        _applyScale = applyScale;
 
        // Subscribe first so a paint between subscription and the size check is not missed.
        _adapter.Resized += OnResized;
        try
        {
            TryEstablish(_adapter.Width, _adapter.Height);
        }
        catch
        {
            _adapter.Resized -= OnResized;
            throw;
        }
    }

    private void OnResized(RenderSurfaceAdapterResizedEventArgs args)
        => TryEstablish(args.NewWidth, args.NewHeight);

    private void TryEstablish(int width, int height)
    {
        // WebGL uses a 1x1 placeholder until its first real paint.
        if (_disposed || _established || width <= 1 || height <= 1)
            return;
 
        // Round physical size outwards: never crop the requested logical game board.
        float scale = Math.Max((float)_logicalWidth / width, (float)_logicalHeight / height);
        _applyScale(scale);
        _established = true;
        _adapter.Resized -= OnResized;
    }

    public void Dispose()
    {
        if (_disposed)
            return;
 
        _disposed = true;
        _adapter.Resized -= OnResized;
    }
}