Dispose of graphics resources deterministically.

Textures, FrameBuffers and VertexBuffers allocated by the Sdl2 Renderer were only being released via finalizers. This could lead to OpenGL out of memory errors since resources may not be cleaned up in a timely manner. To avoid this, IDisposable has been implemented and transitively applied to classes that use these resources.

As a side-effect some static state is no longer static, particularly in Renderer, in order to facilitate this change and just for nicer design in general.

Also dispose some bitmaps.

OpenRA.Renderer.Sdl2/FrameBuffer.cs

@@ -16,11 +16,12 @@ using OpenTK.Graphics.OpenGL;
 
 namespace OpenRA.Renderer.Sdl2
 {
-	public class FrameBuffer : IFrameBuffer
+	public sealed class FrameBuffer : IFrameBuffer
 	{
 		Texture texture;
 		Size size;
 		int framebuffer, depth;
+		bool disposed;
 
 		public FrameBuffer(Size size)
 		{
@@ -81,16 +82,6 @@ namespace OpenRA.Renderer.Sdl2
 			return v;
 		}
 
-		void FinalizeInner()
-		{
-			GL.Ext.DeleteFramebuffers(1, ref framebuffer);
-			ErrorHandler.CheckGlError();
-			GL.Ext.DeleteRenderbuffers(1, ref depth);
-			ErrorHandler.CheckGlError();
-		}
-
-		~FrameBuffer() { Game.RunAfterTick(FinalizeInner); }
-
 		int[] cv = new int[4];
 		public void Bind()
 		{
@@ -120,5 +111,29 @@ namespace OpenRA.Renderer.Sdl2
 		}
 
 		public ITexture Texture { get { return texture; } }
+
+		~FrameBuffer()
+		{
+			Game.RunAfterTick(() => Dispose(false));
+		}
+
+		public void Dispose()
+		{
+			Game.RunAfterTick(() => Dispose(true));
+			GC.SuppressFinalize(this);
+		}
+
+		void Dispose(bool disposing)
+		{
+			if (disposed)
+				return;
+			disposed = true;
+			if (disposing)
+				texture.Dispose();
+			GL.Ext.DeleteFramebuffers(1, ref framebuffer);
+			ErrorHandler.CheckGlError();
+			GL.Ext.DeleteRenderbuffers(1, ref depth);
+			ErrorHandler.CheckGlError();
+		}
 	}
 }