add null sound driver

stepmania/src/StepMania.dsp

@@ -621,6 +621,10 @@ SOURCE=.\arch\Sound\RageSoundDriver_DSound_Software.h
 # End Source File
 # Begin Source File
 
+SOURCE=.\arch\Sound\RageSoundDriver_Null.h
+# End Source File
+# Begin Source File
+
 SOURCE=.\arch\Sound\RageSoundDriver_WaveOut.cpp
 # End Source File
 # Begin Source File

stepmania/src/StepMania.vcproj

@@ -773,6 +773,9 @@ cl /Zl /nologo /c verstub.cpp /Fo$(IntDir)\
 					<File
 						RelativePath="arch\Sound\RageSoundDriver_DSound_Software.h">
 					</File>
+					<File
+						RelativePath="arch\Sound\RageSoundDriver_Null.h">
+					</File>
 					<File
 						RelativePath="arch\Sound\RageSoundDriver_WaveOut.cpp">
 					</File>

stepmania/src/arch/Sound/RageSoundDriver_Null.h

@@ -0,0 +1,22 @@
+#ifndef RAGE_SOUND_NULL
+#define RAGE_SOUND_NULL
+
+#include "RageSound.h"
+
+class RageSound_Null: public RageSoundDriver
+{
+public:
+	/* virtuals: */
+	void StartMixing(RageSound *snd) { }
+	void StopMixing(RageSound *snd) { }
+	int GetPosition(const RageSound *snd) const { return 0; }
+	float GetPlayLatency() const { return 0.0f; } /* silence is fast! */
+};
+
+#endif
+
+/*
+ * Copyright (c) 2003 by the person(s) listed below.  All rights reserved.
+ *
+ * Glenn Maynard
+ */

stepmania/src/arch/arch.cpp

@@ -41,8 +41,10 @@ RageSoundDriver *MakeRageSoundDriver(CString drivers)
 			else if(DriversToTry[i] == "DirectSound-sw") ret = new RageSound_DSound_Software;
 			else if(DriversToTry[i] == "WaveOut") ret = new RageSound_WaveOut;
 #else
-#error No sound drivers defined!
+#warn No sound drivers defined!
+			if(0) ;
 #endif
+			else if(DriversToTry[i] == "Null") ret = new RageSound_Null;
 			else
 				LOG->Warn("Unknown sound driver name: %s", DriversToTry[i].GetString());
 		}

stepmania/src/arch/arch_default.h

@@ -8,8 +8,7 @@
 #include "LoadingWindow/LoadingWindow_SDL.h"
 #include "ErrorDialog/ErrorDialog_stdout.h"
 #include "ArchHooks/ArchHooks_none.h"
-
+#include "Sound/RageSoundDriver_Null.h"
-/* no default sound driver */
 
 #endif