AvaloniaBitmapRenderSurfaceControl.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Media;
using Avalonia.Media.Imaging;
using Gondwana.Rendering;
using Gondwana.Rendering.Backbuffers;
 
namespace Gondwana.Avalonia.Rendering;

public class AvaloniaBitmapRenderSurfaceControl : Control
{
    private WriteableBitmap? _bitmap;

    public AvaloniaBitmapRenderSurfaceAdapter Adapter { get; }

    public RenderSurfaceHost<BitmapBackbuffer> Host { get; }

    public AvaloniaBitmapRenderSurfaceControl()
    {
        Adapter = new AvaloniaBitmapRenderSurfaceAdapter(this);
        Host = new RenderSurfaceHost<BitmapBackbuffer>(Adapter);
 
        SizeChanged += (_, _) => Adapter.RefreshDestinationSize();
    }

    internal void SetBitmap(WriteableBitmap bitmap) => _bitmap = bitmap;

    public override void Render(DrawingContext context)
    {
        context.FillRectangle(Brushes.Black, new Rect(Bounds.Size));
        RenderOptions.SetBitmapInterpolationMode(this,
            Engine.Instance.Configuration.RenderScalingFilter == RenderScalingFilter.NearestNeighbor
                ? BitmapInterpolationMode.None : BitmapInterpolationMode.LowQuality);
        var bmp = _bitmap;
        if (bmp != null)
        {
            var fit = PresentationTransform.Fit(bmp.PixelSize.Width, bmp.PixelSize.Height, Adapter.Width, Adapter.Height).DestinationRect;
            var dest = new Rect(fit.Left, fit.Top, fit.Width, fit.Height);
            context.DrawImage(bmp, new Rect(bmp.Size), dest);
        }
    }
}