Corrected issue on OSX with High DPI display

Many thanks to Marcelo Paez (paezao)

README.md

@@ -249,6 +249,7 @@ contributing (in some way or another) to make raylib project better. Huge thanks
  - [Chris Hemingway](https://github.com/cHemingway) for improving raylib on OSX build system.
  - [Emanuele Petriglia](https://github.com/LelixSuper) for working on multiple GNU/Linux improvements and developing [TicTacToe](https://github.com/LelixSuper/TicTacToe) raylib game.
  - [Joshua Reisenauer](https://github.com/kd7tck) for adding audio modules support (XM, MOD) and reviewing audio system.
+ - Marcelo Paez (paezao) for his help on OSX to solve High DPI display issue. Thanks Marcelo!
  
 	
 [raysan5]: mailto:raysan5@gmail.com "Ramon Santamaria - Ray San"

src/core.c

@@ -1612,16 +1612,7 @@ static void InitGraphicsDevice(int width, int height)
     {
         glfwSwapInterval(1);
         TraceLog(INFO, "Trying to enable VSYNC");
-    }
-
-#ifdef __APPLE__
-    // Get framebuffer size of current window
-    // NOTE: Required to handle HighDPI display correctly
-    // TODO: Probably should be added for other systems too or managed
-    // internally by GLFW3 callback: glfwSetFramebufferSizeCallback()
-    glfwGetFramebufferSize(window, &renderWidth, &renderHeight);
-#endif
-    
+    }   
 #endif // defined(PLATFORM_DESKTOP) || defined(PLATFORM_WEB)
 
 #if defined(PLATFORM_ANDROID) || defined(PLATFORM_RPI)
@@ -1775,9 +1766,19 @@ static void InitGraphicsDevice(int width, int height)
     // NOTE: screenWidth and screenHeight not used, just stored as globals
     rlglInit(screenWidth, screenHeight);
     
+#ifdef __APPLE__
+    // Get framebuffer size of current window
+    // NOTE: Required to handle HighDPI display correctly on OSX because framebuffer 
+    // is automatically reasized to adapt to new DPI.
+    // When OS does that, it can be detected using GLFW3 callback: glfwSetFramebufferSizeCallback()
+    int fbWidth, fbHeight;
+    glfwGetFramebufferSize(window, &fbWidth, &fbHeight);
+    rlViewport(renderOffsetX/2, renderOffsetY/2, fbWidth - renderOffsetX, fbHeight - renderOffsetY);
+#else
     // Initialize screen viewport (area of the screen that you will actually draw to)
     // NOTE: Viewport must be recalculated if screen is resized
     rlViewport(renderOffsetX/2, renderOffsetY/2, renderWidth - renderOffsetX, renderHeight - renderOffsetY);
+#endif
 
     // Initialize internal projection and modelview matrices
     // NOTE: Default to orthographic projection mode with top-left corner at (0,0)