The bones of what will become a Metal backend.

This isn't anywhere close to usable (not even a blank screen will work), let alone complete. It's about 20% done.

src/modules/graphics/metal/Metal.h

@@ -0,0 +1,48 @@
+/**
+ * Copyright (c) 2006-2020 LOVE Development Team
+ *
+ * This software is provided 'as-is', without any express or implied
+ * warranty.  In no event will the authors be held liable for any damages
+ * arising from the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not
+ *    claim that you wrote the original software. If you use this software
+ *    in a product, an acknowledgment in the product documentation would be
+ *    appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *    misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ **/
+
+#pragma once
+
+#include "graphics/Texture.h"
+#include "common/pixelformat.h"
+
+#import <Metal/Metal.h>
+
+namespace love
+{
+namespace graphics
+{
+namespace metal
+{
+
+class Metal
+{
+public:
+
+	static MTLTextureType getTextureType(TextureType type, int msaa);
+	static MTLPixelFormat convertPixelFormat(PixelFormat format, bool &isSRGB);
+
+}; // Metal
+
+extern Metal metal;
+
+} // metal
+} // graphics
+} // love