macOS: fix colors appearing oversaturated on P3 displays.

The fix only applies to macOS 11+ when using OpenGL.

src/common/macosx.h

@@ -27,6 +27,8 @@
 
 #include <string>
 
+typedef struct SDL_Window SDL_Window;
+
 namespace love
 {
 namespace macosx
@@ -55,6 +57,12 @@ std::string getExecutablePath();
  **/
 void requestAttention(bool continuous);
 
+/**
+ * Explicitly sets the window's color space to be sRGB - which stops the OS
+ * from interpreting the backbuffer output as P3 on P3-capable displays.
+ **/
+void setWindowSRGBColorSpace(SDL_Window *window);
+
 } // macosx
 } // love
 

src/common/macosx.mm

@@ -26,9 +26,11 @@
 #import <Cocoa/Cocoa.h>
 
 #ifdef LOVE_MACOSX_SDL_DIRECT_INCLUDE
-# include <SDL.h>
+#include <SDL.h>
+#include <SDL_syswm.h>
 #else
-# include <SDL2/SDL.h>
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_syswm.h>
 #endif
 
 namespace love
@@ -93,6 +95,21 @@ void requestAttention(bool continuous)
 	}
 }
 
+void setWindowSRGBColorSpace(SDL_Window *window)
+{
+	@autoreleasepool
+	{
+		// This works on earlier macOS versions, but performance may be worse
+		// (at least, it was back when I tested in December 2016).
+		if (@available(macOS 11.0, *))
+		{
+			SDL_SysWMinfo info = {};
+			if (SDL_GetWindowWMInfo(window, &info))
+				info.info.cocoa.window.colorSpace = [NSColorSpace sRGBColorSpace];
+		}
+	}
+}
+
 } // osx
 } // love