Layout drawing is super slow

[MainMemory]

Editing Scene34.bin is practically unusable.

[MainMemory]

I've partially improved performance, but it's still rather slow if you have a large window. The diagnostic profiler points to the culprit being System.Drawing.Graphics.DrawImage, which is where the final image is drawn onto the panel. The only solution I can come up with is to drop GDI+ and switch to DirectX/OpenGL.