Audio hotplug fixes for winmm and XAudio2 backends.

src/audio/SDL_audio.c

@@ -299,7 +299,7 @@ add_audio_device(const char *name, void *handle, SDL_AudioDeviceItem **devices,
         return -1;
     }
 
-    SDL_assert(handle != NULL);
+    SDL_assert(handle != NULL);  /* we reserve NULL, audio backends can't use it. */
 
     item->handle = handle;
     SDL_strlcpy(item->name, name, size - sizeof (SDL_AudioDeviceItem));

src/audio/winmm/SDL_winmm.c

@@ -46,7 +46,7 @@ static void DetectWave##typ##Devs(void) { \
         if (wave##typ##GetDevCaps(i,&caps,sizeof(caps))==MMSYSERR_NOERROR) { \
             char *name = WIN_StringToUTF8(caps.szPname); \
             if (name != NULL) { \
-                SDL_AddAudioDevice((int) iscapture, name, (void *) ((size_t) i)); \
+                SDL_AddAudioDevice((int) iscapture, name, (void *) ((size_t) i+1)); \
                 SDL_free(name); \
             } \
         } \
@@ -228,7 +228,8 @@ WINMM_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
     UINT i;
 
     if (handle != NULL) {  /* specific device requested? */
-        const size_t val = (size_t) handle;
+        /* -1 because we increment the original value to avoid NULL. */
+        const size_t val = ((size_t) handle) - 1;
         devId = (UINT) val;
     }
 

src/audio/xaudio2/SDL_xaudio2.c

@@ -146,7 +146,7 @@ XAUDIO2_DetectDevices(void)
         if (IXAudio2_GetDeviceDetails(ixa2, i, &details) == S_OK) {
             char *str = WIN_StringToUTF8(details.DisplayName);
             if (str != NULL) {
-                SDL_AddAudioDevice(SDL_FALSE, str, (void *) ((size_t) i));
+                SDL_AddAudioDevice(SDL_FALSE, str, (void *) ((size_t) i+1));
                 SDL_free(str);  /* SDL_AddAudioDevice made a copy of the string. */
             }
         }
@@ -297,7 +297,7 @@ XAUDIO2_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
 #if defined(SDL_XAUDIO2_WIN8)
     LPCWSTR devId = NULL;
 #else
-    UINT32 devId = (UINT32) ((size_t) handle);  /* 0 == system default device. */
+    UINT32 devId = 0;  /* 0 == system default device. */
 #endif
 
     static IXAudio2VoiceCallbackVtbl callbacks_vtable = {
@@ -312,6 +312,16 @@ XAUDIO2_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
 
     static IXAudio2VoiceCallback callbacks = { &callbacks_vtable };
 
+#if defined(SDL_XAUDIO2_WIN8)
+    /* !!! FIXME: hook up hotplugging. */
+#else
+    if (handle != NULL) {  /* specific device requested? */
+        /* -1 because we increment the original value to avoid NULL. */
+        const size_t val = ((size_t) handle) - 1;
+        devId = (UINT32) val;
+    }
+#endif
+
     if (XAudio2Create(&ixa2, 0, XAUDIO2_DEFAULT_PROCESSOR) != S_OK) {
         return SDL_SetError("XAudio2: XAudio2Create() failed at open.");
     }