Demos - fix for MacOS

Author: RichardGe

tutorials/common/common.h

@@ -3,15 +3,6 @@
 #include <assert.h> 
 #include <iostream>
 
-// creation flags used by most of the Demo.
-// examples:
-// RPR_CREATION_FLAGS_ENABLE_GPU0 <- use the first GPU
-// RPR_CREATION_FLAGS_ENABLE_CPU <- use the first CPU only
-// RPR_CREATION_FLAGS_ENABLE_GPU0 | RPR_CREATION_FLAGS_ENABLE_CPU <- use the first CPU+GPU
-// RPR_CREATION_FLAGS_ENABLE_GPU0 | RPR_CREATION_FLAGS_ENABLE_GPU1 <-- use 2 GPU
-rpr_creation_flags g_ContextCreationFlags = RPR_CREATION_FLAGS_ENABLE_GPU0;
-
-
 // Tahoe plugin is in maintenance mode - no new features planned.
 #if 0
 #if defined(WIN32)
@@ -30,12 +21,24 @@ rpr_creation_flags g_ContextCreationFlags = RPR_CREATION_FLAGS_ENABLE_GPU0;
 #define RPR_PLUGIN_FILE_NAME "libNorthstar64.so"
 #elif defined(__APPLE__)
 #define RPR_PLUGIN_FILE_NAME "libNorthstar64.dylib"
-g_ContextCreationFlags |= RPR_CREATION_FLAGS_ENABLE_METAL; // by default always enable Metal for MacOS
 #endif
 #define USING_NORTHSTAR
 #endif
 
 
+// creation flags used by most of the Demo.
+// examples:
+// RPR_CREATION_FLAGS_ENABLE_GPU0 <- use the first GPU
+// RPR_CREATION_FLAGS_ENABLE_CPU <- use the first CPU only
+// RPR_CREATION_FLAGS_ENABLE_GPU0 | RPR_CREATION_FLAGS_ENABLE_CPU <- use the first CPU+GPU
+// RPR_CREATION_FLAGS_ENABLE_GPU0 | RPR_CREATION_FLAGS_ENABLE_GPU1 <-- use 2 GPU
+const rpr_creation_flags g_ContextCreationFlags = RPR_CREATION_FLAGS_ENABLE_GPU0
+	#if defined(USING_NORTHSTAR) && defined(__APPLE__)
+	| RPR_CREATION_FLAGS_ENABLE_METAL // by default always enable Metal for MacOS
+	#endif
+	;
+
+
 // Structure to describe vertex layout
 struct vertex
 {