windows: Move IMMDevice work to common file, implement DirectSound enumeration support

2025-09-28 14:08:28 +00:00 · 2022-07-10 12:59:33 -04:00
parent 2373da5d94
commit ae105ae1c7
12 changed files with 695 additions and 420 deletions
--- a/src/core/windows/SDL_immdevice.c
+++ b/src/core/windows/SDL_immdevice.c
@@ -0,0 +1,486 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+#include "../../SDL_internal.h"
+
+#if (defined(__WIN32__) || defined(__GDK__)) && HAVE_MMDEVICEAPI_H
+
+#include "SDL_windows.h"
+#include "SDL_immdevice.h"
+#include "../../audio/SDL_sysaudio.h"
+#include <objbase.h> /* For CLSIDFromString */
+
+static const ERole SDL_IMMDevice_role = eConsole;  /* !!! FIXME: should this be eMultimedia? Should be a hint? */
+
+/* This is global to the WASAPI target, to handle hotplug and default device lookup. */
+static IMMDeviceEnumerator *enumerator = NULL;
+
+/* PropVariantInit() is an inline function/macro in PropIdl.h that calls the C runtime's memset() directly. Use ours instead, to avoid dependency. */
+#ifdef PropVariantInit
+#undef PropVariantInit
+#endif
+#define PropVariantInit(p) SDL_zerop(p)
+
+/* Some GUIDs we need to know without linking to libraries that aren't available before Vista. */
+static const CLSID SDL_CLSID_MMDeviceEnumerator = { 0xbcde0395, 0xe52f, 0x467c,{ 0x8e, 0x3d, 0xc4, 0x57, 0x92, 0x91, 0x69, 0x2e } };
+static const IID SDL_IID_IMMDeviceEnumerator = { 0xa95664d2, 0x9614, 0x4f35,{ 0xa7, 0x46, 0xde, 0x8d, 0xb6, 0x36, 0x17, 0xe6 } };
+static const IID SDL_IID_IMMNotificationClient = { 0x7991eec9, 0x7e89, 0x4d85,{ 0x83, 0x90, 0x6c, 0x70, 0x3c, 0xec, 0x60, 0xc0 } };
+static const IID SDL_IID_IMMEndpoint = { 0x1be09788, 0x6894, 0x4089,{ 0x85, 0x86, 0x9a, 0x2a, 0x6c, 0x26, 0x5a, 0xc5 } };
+static const PROPERTYKEY SDL_PKEY_Device_FriendlyName = { { 0xa45c254e, 0xdf1c, 0x4efd,{ 0x80, 0x20, 0x67, 0xd1, 0x46, 0xa8, 0x50, 0xe0, } }, 14 };
+static const PROPERTYKEY SDL_PKEY_AudioEngine_DeviceFormat = { { 0xf19f064d, 0x82c, 0x4e27,{ 0xbc, 0x73, 0x68, 0x82, 0xa1, 0xbb, 0x8e, 0x4c, } }, 0 };
+static const PROPERTYKEY SDL_PKEY_AudioEndpoint_GUID = { { 0x1da5d803, 0xd492, 0x4edd,{ 0x8c, 0x23, 0xe0, 0xc0, 0xff, 0xee, 0x7f, 0x0e, } }, 4 };
+static const GUID SDL_KSDATAFORMAT_SUBTYPE_PCM = { 0x00000001, 0x0000, 0x0010,{ 0x80, 0x00, 0x00, 0xaa, 0x00, 0x38, 0x9b, 0x71 } };
+static const GUID SDL_KSDATAFORMAT_SUBTYPE_IEEE_FLOAT = { 0x00000003, 0x0000, 0x0010,{ 0x80, 0x00, 0x00, 0xaa, 0x00, 0x38, 0x9b, 0x71 } };
+
+/* these increment as default devices change. Opened default devices pick up changes in their threads. */
+SDL_atomic_t SDL_IMMDevice_DefaultPlaybackGeneration;
+SDL_atomic_t SDL_IMMDevice_DefaultCaptureGeneration;
+
+static void
+GetMMDeviceInfo(IMMDevice *device, char **utf8dev, WAVEFORMATEXTENSIBLE *fmt, GUID *guid)
+{
+    /* PKEY_Device_FriendlyName gives you "Speakers (SoundBlaster Pro)" which drives me nuts. I'd rather it be
+       "SoundBlaster Pro (Speakers)" but I guess that's developers vs users. Windows uses the FriendlyName in
+       its own UIs, like Volume Control, etc. */
+    IPropertyStore *props = NULL;
+    *utf8dev = NULL;
+    SDL_zerop(fmt);
+    if (SUCCEEDED(IMMDevice_OpenPropertyStore(device, STGM_READ, &props))) {
+        PROPVARIANT var;
+        PropVariantInit(&var);
+        if (SUCCEEDED(IPropertyStore_GetValue(props, &SDL_PKEY_Device_FriendlyName, &var))) {
+            *utf8dev = WIN_StringToUTF8W(var.pwszVal);
+        }
+        PropVariantClear(&var);
+        if (SUCCEEDED(IPropertyStore_GetValue(props, &SDL_PKEY_AudioEngine_DeviceFormat, &var))) {
+            SDL_memcpy(fmt, var.blob.pBlobData, SDL_min(var.blob.cbSize, sizeof(WAVEFORMATEXTENSIBLE)));
+        }
+        PropVariantClear(&var);
+        if (SUCCEEDED(IPropertyStore_GetValue(props, &SDL_PKEY_AudioEndpoint_GUID, &var))) {
+            CLSIDFromString(var.pwszVal, guid);
+        }
+        PropVariantClear(&var);
+        IPropertyStore_Release(props);
+    }
+}
+
+/* This is a list of device id strings we have inflight, so we have consistent pointers to the same device. */
+typedef struct DevIdList
+{
+    WCHAR *str;
+    LPGUID guid;
+    struct DevIdList *next;
+} DevIdList;
+
+static DevIdList *deviceid_list = NULL;
+
+static void
+SDL_IMMDevice_Remove(const SDL_bool iscapture, LPCWSTR devid, SDL_bool useguid)
+{
+    DevIdList *i;
+    DevIdList *next;
+    DevIdList *prev = NULL;
+    for (i = deviceid_list; i; i = next) {
+        next = i->next;
+        if (SDL_wcscmp(i->str, devid) == 0) {
+            if (prev) {
+                prev->next = next;
+            } else {
+                deviceid_list = next;
+            }
+            SDL_RemoveAudioDevice(iscapture, useguid ? ((void *) i->guid) : ((void *) i->str));
+            SDL_free(i->str);
+            SDL_free(i);
+        }
+        prev = i;
+    }
+}
+
+static void
+SDL_IMMDevice_Add(const SDL_bool iscapture, const char *devname, WAVEFORMATEXTENSIBLE *fmt, LPCWSTR devid, GUID *dsoundguid, SDL_bool useguid)
+{
+    DevIdList *devidlist;
+    SDL_AudioSpec spec;
+    LPGUID cpyguid;
+
+    /* You can have multiple endpoints on a device that are mutually exclusive ("Speakers" vs "Line Out" or whatever).
+       In a perfect world, things that are unplugged won't be in this collection. The only gotcha is probably for
+       phones and tablets, where you might have an internal speaker and a headphone jack and expect both to be
+       available and switch automatically. (!!! FIXME...?) */
+
+       /* see if we already have this one. */
+    for (devidlist = deviceid_list; devidlist; devidlist = devidlist->next) {
+        if (SDL_wcscmp(devidlist->str, devid) == 0) {
+            return;  /* we already have this. */
+        }
+    }
+
+    devidlist = (DevIdList *)SDL_malloc(sizeof(*devidlist));
+    if (!devidlist) {
+        return;  /* oh well. */
+    }
+
+    devid = SDL_wcsdup(devid);
+    if (!devid) {
+        SDL_free(devidlist);
+        return;  /* oh well. */
+    }
+
+    cpyguid = (LPGUID)SDL_malloc(sizeof(GUID));
+    if (!cpyguid) {
+        SDL_free(devidlist);
+        return; /* oh well. */
+    }
+    SDL_memcpy(cpyguid, dsoundguid, sizeof(GUID));
+
+    devidlist->str = (WCHAR *)devid;
+    devidlist->guid = cpyguid;
+    devidlist->next = deviceid_list;
+    deviceid_list = devidlist;
+
+    SDL_zero(spec);
+    spec.channels = (Uint8)fmt->Format.nChannels;
+    spec.freq = fmt->Format.nSamplesPerSec;
+    spec.format = WaveFormatToSDLFormat((WAVEFORMATEX *)fmt);
+    SDL_AddAudioDevice(iscapture, devname, &spec, useguid ? ((void *) cpyguid) : ((void *) devid));
+}
+
+/* We need a COM subclass of IMMNotificationClient for hotplug support, which is
+   easy in C++, but we have to tapdance more to make work in C.
+   Thanks to this page for coaching on how to make this work:
+     https://www.codeproject.com/Articles/13601/COM-in-plain-C */
+
+typedef struct SDLMMNotificationClient
+{
+    const IMMNotificationClientVtbl *lpVtbl;
+    SDL_atomic_t refcount;
+    SDL_bool useguid;
+} SDLMMNotificationClient;
+
+static HRESULT STDMETHODCALLTYPE
+SDLMMNotificationClient_QueryInterface(IMMNotificationClient *this, REFIID iid, void **ppv)
+{
+    if ((WIN_IsEqualIID(iid, &IID_IUnknown)) || (WIN_IsEqualIID(iid, &SDL_IID_IMMNotificationClient))) {
+        *ppv = this;
+        this->lpVtbl->AddRef(this);
+        return S_OK;
+    }
+
+    *ppv = NULL;
+    return E_NOINTERFACE;
+}
+
+static ULONG STDMETHODCALLTYPE
+SDLMMNotificationClient_AddRef(IMMNotificationClient *ithis)
+{
+    SDLMMNotificationClient *this = (SDLMMNotificationClient *)ithis;
+    return (ULONG)(SDL_AtomicIncRef(&this->refcount) + 1);
+}
+
+static ULONG STDMETHODCALLTYPE
+SDLMMNotificationClient_Release(IMMNotificationClient *ithis)
+{
+    /* this is a static object; we don't ever free it. */
+    SDLMMNotificationClient *this = (SDLMMNotificationClient *)ithis;
+    const ULONG retval = SDL_AtomicDecRef(&this->refcount);
+    if (retval == 0) {
+        SDL_AtomicSet(&this->refcount, 0);  /* uhh... */
+        return 0;
+    }
+    return retval - 1;
+}
+
+/* These are the entry points called when WASAPI device endpoints change. */
+static HRESULT STDMETHODCALLTYPE
+SDLMMNotificationClient_OnDefaultDeviceChanged(IMMNotificationClient *ithis, EDataFlow flow, ERole role, LPCWSTR pwstrDeviceId)
+{
+    if (role != SDL_IMMDevice_role) {
+        return S_OK;  /* ignore it. */
+    }
+
+    /* Increment the "generation," so opened devices will pick this up in their threads. */
+    switch (flow) {
+    case eRender:
+        SDL_AtomicAdd(&SDL_IMMDevice_DefaultPlaybackGeneration, 1);
+        break;
+
+    case eCapture:
+        SDL_AtomicAdd(&SDL_IMMDevice_DefaultCaptureGeneration, 1);
+        break;
+
+    case eAll:
+        SDL_AtomicAdd(&SDL_IMMDevice_DefaultPlaybackGeneration, 1);
+        SDL_AtomicAdd(&SDL_IMMDevice_DefaultCaptureGeneration, 1);
+        break;
+
+    default:
+        SDL_assert(!"uhoh, unexpected OnDefaultDeviceChange flow!");
+        break;
+    }
+
+    return S_OK;
+}
+
+static HRESULT STDMETHODCALLTYPE
+SDLMMNotificationClient_OnDeviceAdded(IMMNotificationClient *ithis, LPCWSTR pwstrDeviceId)
+{
+    /* we ignore this; devices added here then progress to ACTIVE, if appropriate, in
+       OnDeviceStateChange, making that a better place to deal with device adds. More
+       importantly: the first time you plug in a USB audio device, this callback will
+       fire, but when you unplug it, it isn't removed (it's state changes to NOTPRESENT).
+       Plugging it back in won't fire this callback again. */
+    return S_OK;
+}
+
+static HRESULT STDMETHODCALLTYPE
+SDLMMNotificationClient_OnDeviceRemoved(IMMNotificationClient *ithis, LPCWSTR pwstrDeviceId)
+{
+    /* See notes in OnDeviceAdded handler about why we ignore this. */
+    return S_OK;
+}
+
+static HRESULT STDMETHODCALLTYPE
+SDLMMNotificationClient_OnDeviceStateChanged(IMMNotificationClient *ithis, LPCWSTR pwstrDeviceId, DWORD dwNewState)
+{
+    IMMDevice *device = NULL;
+
+    if (SUCCEEDED(IMMDeviceEnumerator_GetDevice(enumerator, pwstrDeviceId, &device))) {
+        IMMEndpoint *endpoint = NULL;
+        if (SUCCEEDED(IMMDevice_QueryInterface(device, &SDL_IID_IMMEndpoint, (void **)&endpoint))) {
+            EDataFlow flow;
+            if (SUCCEEDED(IMMEndpoint_GetDataFlow(endpoint, &flow))) {
+                const SDL_bool iscapture = (flow == eCapture);
+                const SDLMMNotificationClient *client = (SDLMMNotificationClient*) ithis;
+                if (dwNewState == DEVICE_STATE_ACTIVE) {
+                    char *utf8dev;
+                    WAVEFORMATEXTENSIBLE fmt;
+                    GUID dsoundguid;
+                    GetMMDeviceInfo(device, &utf8dev, &fmt, &dsoundguid);
+                    if (utf8dev) {
+                        SDL_IMMDevice_Add(iscapture, utf8dev, &fmt, pwstrDeviceId, &dsoundguid, client->useguid);
+                        SDL_free(utf8dev);
+                    }
+                } else {
+                    SDL_IMMDevice_Remove(iscapture, pwstrDeviceId, client->useguid);
+                }
+            }
+            IMMEndpoint_Release(endpoint);
+        }
+        IMMDevice_Release(device);
+    }
+
+    return S_OK;
+}
+
+static HRESULT STDMETHODCALLTYPE
+SDLMMNotificationClient_OnPropertyValueChanged(IMMNotificationClient *this, LPCWSTR pwstrDeviceId, const PROPERTYKEY key)
+{
+    return S_OK;  /* we don't care about these. */
+}
+
+static const IMMNotificationClientVtbl notification_client_vtbl = {
+    SDLMMNotificationClient_QueryInterface,
+    SDLMMNotificationClient_AddRef,
+    SDLMMNotificationClient_Release,
+    SDLMMNotificationClient_OnDeviceStateChanged,
+    SDLMMNotificationClient_OnDeviceAdded,
+    SDLMMNotificationClient_OnDeviceRemoved,
+    SDLMMNotificationClient_OnDefaultDeviceChanged,
+    SDLMMNotificationClient_OnPropertyValueChanged
+};
+
+static SDLMMNotificationClient notification_client = { &notification_client_vtbl, { 1 } };
+
+int
+SDL_IMMDevice_Init(void)
+{
+    HRESULT ret;
+
+    SDL_AtomicSet(&SDL_IMMDevice_DefaultPlaybackGeneration, 1);
+    SDL_AtomicSet(&SDL_IMMDevice_DefaultCaptureGeneration, 1);
+
+    /* just skip the discussion with COM here. */
+    if (!WIN_IsWindowsVistaOrGreater()) {
+        return SDL_SetError("WASAPI support requires Windows Vista or later");
+    }
+
+    if (FAILED(WIN_CoInitialize())) {
+        return SDL_SetError("WASAPI: CoInitialize() failed");
+    }
+
+    ret = CoCreateInstance(&SDL_CLSID_MMDeviceEnumerator, NULL, CLSCTX_INPROC_SERVER, &SDL_IID_IMMDeviceEnumerator, (LPVOID *)&enumerator);
+    if (FAILED(ret)) {
+        WIN_CoUninitialize();
+        return WIN_SetErrorFromHRESULT("WASAPI CoCreateInstance(MMDeviceEnumerator)", ret);
+    }
+    return 0;
+}
+
+void
+SDL_IMMDevice_Quit(void)
+{
+    if (enumerator) {
+        IMMDeviceEnumerator_UnregisterEndpointNotificationCallback(enumerator, (IMMNotificationClient *)&notification_client);
+        IMMDeviceEnumerator_Release(enumerator);
+        enumerator = NULL;
+    }
+}
+
+int
+SDL_IMMDevice_Get(LPCWSTR devid, IMMDevice **device, SDL_bool iscapture)
+{
+    HRESULT ret;
+
+    SDL_assert(device != NULL);
+
+    if (devid == NULL) {
+        const EDataFlow dataflow = iscapture ? eCapture : eRender;
+        ret = IMMDeviceEnumerator_GetDefaultAudioEndpoint(enumerator, dataflow, SDL_IMMDevice_role, device);
+    } else {
+        ret = IMMDeviceEnumerator_GetDevice(enumerator, devid, device);
+    }
+
+    if (FAILED(ret)) {
+        SDL_assert(*device == NULL);
+        return WIN_SetErrorFromHRESULT("WASAPI can't find requested audio endpoint", ret);
+    }
+    return 0;
+}
+
+typedef struct
+{
+    LPWSTR devid;
+    char *devname;
+    WAVEFORMATEXTENSIBLE fmt;
+    GUID dsoundguid;
+} EndpointItem;
+
+static int SDLCALL sort_endpoints(const void *_a, const void *_b)
+{
+    LPWSTR a = ((const EndpointItem *)_a)->devid;
+    LPWSTR b = ((const EndpointItem *)_b)->devid;
+    if (!a && b) {
+        return -1;
+    } else if (a && !b) {
+        return 1;
+    }
+
+    while (SDL_TRUE) {
+        if (*a < *b) {
+            return -1;
+        } else if (*a > *b) {
+            return 1;
+        } else if (*a == 0) {
+            break;
+        }
+        a++;
+        b++;
+    }
+
+    return 0;
+}
+
+static void
+EnumerateEndpointsForFlow(const SDL_bool iscapture)
+{
+    IMMDeviceCollection *collection = NULL;
+    EndpointItem *items;
+    UINT i, total;
+
+    /* Note that WASAPI separates "adapter devices" from "audio endpoint devices"
+       ...one adapter device ("SoundBlaster Pro") might have multiple endpoint devices ("Speakers", "Line-Out"). */
+
+    if (FAILED(IMMDeviceEnumerator_EnumAudioEndpoints(enumerator, iscapture ? eCapture : eRender, DEVICE_STATE_ACTIVE, &collection))) {
+        return;
+    }
+
+    if (FAILED(IMMDeviceCollection_GetCount(collection, &total))) {
+        IMMDeviceCollection_Release(collection);
+        return;
+    }
+
+    items = (EndpointItem *)SDL_calloc(total, sizeof(EndpointItem));
+    if (!items) {
+        return;  /* oh well. */
+    }
+
+    for (i = 0; i < total; i++) {
+        EndpointItem *item = items + i;
+        IMMDevice *device = NULL;
+        if (SUCCEEDED(IMMDeviceCollection_Item(collection, i, &device))) {
+            if (SUCCEEDED(IMMDevice_GetId(device, &item->devid))) {
+                GetMMDeviceInfo(device, &item->devname, &item->fmt, &item->dsoundguid);
+            }
+            IMMDevice_Release(device);
+        }
+    }
+
+    /* sort the list of devices by their guid so list is consistent between runs */
+    SDL_qsort(items, total, sizeof(*items), sort_endpoints);
+
+    /* Send the sorted list on to the SDL's higher level. */
+    for (i = 0; i < total; i++) {
+        EndpointItem *item = items + i;
+        if ((item->devid) && (item->devname)) {
+            SDL_IMMDevice_Add(iscapture, item->devname, &item->fmt, item->devid, &item->dsoundguid, notification_client.useguid);
+        }
+        SDL_free(item->devname);
+        CoTaskMemFree(item->devid);
+    }
+
+    SDL_free(items);
+    IMMDeviceCollection_Release(collection);
+}
+
+void
+SDL_IMMDevice_EnumerateEndpoints(SDL_bool useguid)
+{
+    notification_client.useguid = useguid;
+
+    EnumerateEndpointsForFlow(SDL_FALSE);  /* playback */
+    EnumerateEndpointsForFlow(SDL_TRUE);  /* capture */
+
+    /* if this fails, we just won't get hotplug events. Carry on anyhow. */
+    IMMDeviceEnumerator_RegisterEndpointNotificationCallback(enumerator, (IMMNotificationClient *)&notification_client);
+}
+
+SDL_AudioFormat
+WaveFormatToSDLFormat(WAVEFORMATEX *waveformat)
+{
+    if ((waveformat->wFormatTag == WAVE_FORMAT_IEEE_FLOAT) && (waveformat->wBitsPerSample == 32)) {
+        return AUDIO_F32SYS;
+    } else if ((waveformat->wFormatTag == WAVE_FORMAT_PCM) && (waveformat->wBitsPerSample == 16)) {
+        return AUDIO_S16SYS;
+    } else if ((waveformat->wFormatTag == WAVE_FORMAT_PCM) && (waveformat->wBitsPerSample == 32)) {
+        return AUDIO_S32SYS;
+    } else if (waveformat->wFormatTag == WAVE_FORMAT_EXTENSIBLE) {
+        const WAVEFORMATEXTENSIBLE *ext = (const WAVEFORMATEXTENSIBLE *)waveformat;
+        if ((SDL_memcmp(&ext->SubFormat, &SDL_KSDATAFORMAT_SUBTYPE_IEEE_FLOAT, sizeof(GUID)) == 0) && (waveformat->wBitsPerSample == 32)) {
+            return AUDIO_F32SYS;
+        } else if ((SDL_memcmp(&ext->SubFormat, &SDL_KSDATAFORMAT_SUBTYPE_PCM, sizeof(GUID)) == 0) && (waveformat->wBitsPerSample == 16)) {
+            return AUDIO_S16SYS;
+        } else if ((SDL_memcmp(&ext->SubFormat, &SDL_KSDATAFORMAT_SUBTYPE_PCM, sizeof(GUID)) == 0) && (waveformat->wBitsPerSample == 32)) {
+            return AUDIO_S32SYS;
+        }
+    }
+    return 0;
+}
+
+#endif /* (defined(__WIN32__) || defined(__GDK__)) && HAVE_MMDEVICEAPI_H */
--- a/src/core/windows/SDL_immdevice.h
+++ b/src/core/windows/SDL_immdevice.h
@@ -0,0 +1,43 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef SDL_IMMDEVICE_H
+#define SDL_IMMDEVICE_H
+
+#include "SDL_atomic.h"
+#include "SDL_audio.h"
+
+#define COBJMACROS
+#include <mmdeviceapi.h>
+#include <mmreg.h>
+
+int SDL_IMMDevice_Init(void);
+void SDL_IMMDevice_Quit(void);
+int SDL_IMMDevice_Get(LPCWSTR devid, IMMDevice **device, SDL_bool iscapture);
+void SDL_IMMDevice_EnumerateEndpoints(SDL_bool useguid);
+
+SDL_AudioFormat WaveFormatToSDLFormat(WAVEFORMATEX *waveformat);
+
+/* these increment as default devices change. Opened default devices pick up changes in their threads. */
+extern SDL_atomic_t SDL_IMMDevice_DefaultPlaybackGeneration;
+extern SDL_atomic_t SDL_IMMDevice_DefaultCaptureGeneration;
+
+#endif /* SDL_IMMDEVICE_H */