Yes, Darwin (and OS X) is POSIX, see

http://www.xyroth-enterprises.co.uk/posixos.htm
SDL is used on OS X for some things, but not all.
Use #if defined(...) instead of #ifdef in most of the Selector_*.h files.

stepmania/src/arch/ArchHooks/Selector_ArchHooks.h

@@ -4,10 +4,10 @@
 #include "arch/arch_platform.h"
 
 /* ArchHooks driver selector. */
-#if   defined(HAVE_DARWIN)
+#if defined(HAVE_DARWIN)
 #include "ArchHooks_darwin.h"
 
-#elif defined(HAVE_POSIX)
+#elif defined(HAVE_UNIX)
 #include "ArchHooks_Unix.h"
 
 #elif defined(HAVE_WIN32) // XXX: Better name for this API?

stepmania/src/arch/Dialog/Selector_Dialog.h

@@ -4,11 +4,10 @@
 #include "arch/arch_platform.h"
 
 /* Dialog drivers selector. */
-#ifdef HAVE_WIN32
+#if defined(HAVE_WIN32)
 #include "DialogDriver_Win32.h"
-#endif
 
-#ifdef HAVE_COCOA
+#elif defined(HAVE_COCOA)
 #include "DialogDriver_Cocoa.h"
 #endif
 

stepmania/src/arch/InputHandler/Selector_InputHandler.h

@@ -17,9 +17,9 @@
 #include "InputHandler_MonkeyKeyboard.h"
 
 // NOTE: If X11 is available, we don't use LLW_SDL, which IH_SDL depends on.
-#ifdef HAVE_X11
+#if defined(HAVE_X11)
 #include "InputHandler_X11.h"
-#elif HAVE_SDL
+#elif defined(HAVE_SDL)
 #include "InputHandler_SDL.h"
 #endif
 

stepmania/src/arch/LoadingWindow/Selector_LoadingWindow.h

@@ -4,25 +4,21 @@
 #include "arch/arch_platform.h"
 
 /* LoadingWindow driver selector. */
-#ifdef HAVE_COCOA
-#include "LoadingWindow_Cocoa.h"
-#endif
-
-#ifdef HAVE_GTK
-#include "LoadingWindow_Gtk.h"
-#endif
-
 #include "LoadingWindow_Null.h"
 
-#ifdef HAVE_SDL
+#if defined(HAVE_COCOA)
+#include "LoadingWindow_Cocoa.h"
+
+#elif defined(HAVE_GTK)
+#include "LoadingWindow_Gtk.h"
+
+#elif defined(HAVE_SDL)
 #include "LoadingWindow_SDL.h"
-#endif
 
-#ifdef HAVE_WIN32
+#elif defined(HAVE_WIN32)
 #include "LoadingWindow_Win32.h"
-#endif
 
-#ifdef HAVE_XBOX
+#elif defined(HAVE_XBOX)
 #include "LoadingWindow_Xbox.h"
 #endif
 

stepmania/src/arch/Sound/Selector_RageSoundDriver.h

@@ -24,10 +24,6 @@
 #include "RageSoundDriver_OSS.h"
 #endif
 
-#ifdef HAVE_QUICKTIME1
-#include "RageSoundDriver_QT1.h"
-#endif
-
 #ifdef HAVE_WIN32
 #include "RageSoundDriver_WaveOut.h"
 #endif

stepmania/src/arch/arch_platform.h

@@ -3,14 +3,14 @@
 
 // In here, you define which APIs are guaranteed to be available on which OSes.
 // Don't ever actually #include anything here -- that's for */Selector_*.h.
-#if defined(UNIX) && !defined(DARWIN) // Darwin isn't POSIX enough for us.
-#define HAVE_POSIX				// (is Darwin POSIX at all?)
+#if defined(UNIX) && !defined(DARWIN)
+#define HAVE_UNIX
 #endif
 #if defined(DARWIN)
 #define HAVE_DARWIN
 #define HAVE_COCOA
 #define HAVE_COREAUDIO
-#define HAVE_QUICKTIME1
+#define HAVE_SDL
 #endif
 #if defined(_WINDOWS)
 #define HAVE_DIRECTX
@@ -21,7 +21,7 @@
 #define HAVE_XBOX // XXX: Better name for this API?
 #endif
 #if defined(LINUX)
-#define HAVE_POSIX	// Here just to be explicit.
+#define HAVE_UNIX	// Here just to be explicit.
 #define HAVE_LINUXKERNEL
 #endif