more presentation API improvements

src/Graphics/CommandBuffer.cs

@@ -664,7 +664,7 @@ namespace MoonWorks.Graphics
 			return new Texture(
 				Device,
 				Refresh.Refresh_AcquireSwapchainTexture(Device.Handle, Handle, window.Handle),
-				(TextureFormat) Refresh.Refresh_GetSwapchainFormat(Device.Handle, window.Handle),
+				Device.GetSwapchainFormat(window),
 				window.Width,
 				window.Height
 			);

src/Graphics/GraphicsDevice.cs

@@ -57,6 +57,11 @@ namespace MoonWorks.Graphics
 			Refresh.Refresh_Wait(Handle);
 		}
 
+		public TextureFormat GetSwapchainFormat(Window window)
+		{
+			return (TextureFormat) Refresh.Refresh_GetSwapchainFormat(Handle, window.Handle);
+		}
+
 		internal void SubmitDestroyCommandBuffer()
 		{
 			if (resourcesToDestroy.Count > 0)

src/Graphics/GraphicsResource.cs

@@ -12,13 +12,16 @@ namespace MoonWorks.Graphics
 
 		private WeakReference<GraphicsResource> selfReference;
 
-		public GraphicsResource(GraphicsDevice device)
+		public GraphicsResource(GraphicsDevice device, bool trackResource = true)
 		{
 			Device = device;
 
+			if (trackResource)
+			{
 				selfReference = new WeakReference<GraphicsResource>(this);
 				Device.AddResourceReference(selfReference);
 			}
+		}
 
 		protected virtual void Dispose(bool disposing)
 		{

src/Graphics/Resources/Texture.cs

@@ -200,13 +200,14 @@ namespace MoonWorks.Graphics
 		}
 
 		// Used by AcquireSwapchainTexture.
+		// Should not be tracked, because swapchain textures are managed by Vulkan.
 		internal Texture(
 			GraphicsDevice device,
 			IntPtr handle,
 			TextureFormat format,
 			uint width,
 			uint height
-		) : base(device)
+		) : base(device, false)
 		{
 			Handle = handle;