Make screen refresh more snappy on macOS

src/macos.h

@@ -37,4 +37,15 @@ const char *apple_picturesPath(void);
 int apple_trash(const char *path);
 
 
+/*
+* It's unclear why we need this on macOS, but the SDL2 library on the Mac
+* appears to require an extra flip during a delay without which the flip does
+* occur but not until the next click or after much time passes.
+*/
+#define SDL_Delay(n) do { \
+    SDL_Flip(screen);         \
+    SDL_Delay(n);             \
+} while(0)
+
+
 #endif /* __MACOS_H__ */

src/tuxpaint.c

@@ -403,18 +403,18 @@ int iswprint(wchar_t wc)
 
 #endif /* WIN32 */
 
-#if defined(__MACOS__)
-#include "macos.h"
-#elif defined(__IOS__)
-#include "ios.h"
-#endif
-
 #include <errno.h>
 #include <sys/stat.h>
 
 #include "SDL2/SDL.h"
 #include "SDL2/SDL_thread.h"
 
+#if defined(__MACOS__)
+#include "macos.h"
+#elif defined(__IOS__)
+#include "ios.h"
+#endif
+
 #if !defined(_SDL_H) && !defined(SDL_h_)
 #error "---------------------------------------------------"
 #error "If you installed SDL from a package, be sure to get"