Moved mouse/keyboard detection to a separate thread on Windows

Getting device names can hang for a long time on certain devices, so make sure this is done on a separate thread to avoid blocking initialization and the main loop.

Fixes https://github.com/libsdl-org/SDL/issues/12913

src/core/windows/SDL_hid.c

@@ -175,12 +175,39 @@ static CM_Register_NotificationFunc CM_Register_Notification;
 static CM_Unregister_NotificationFunc CM_Unregister_Notification;
 static HCMNOTIFICATION s_DeviceNotificationFuncHandle;
 static Uint64 s_LastDeviceNotification = 1;
+static HANDLE s_HotplugEvent = INVALID_HANDLE_VALUE;
+static SDL_AtomicInt s_HotplugRunning;
+static SDL_Thread *s_HotplugThread;
+
+#ifdef SDL_VIDEO_DRIVER_WINDOWS
+// Defined in SDL_windowsevents.c
+extern void WIN_CheckKeyboardAndMouseHotplug(bool hid_loaded);
+#endif
+
+static int SDLCALL DeviceHotplugThread(void *unused)
+{
+    bool hid_loaded = WIN_LoadHIDDLL();
+
+    // Always run the initial device detection
+    do {
+#ifdef SDL_VIDEO_DRIVER_WINDOWS
+        WIN_CheckKeyboardAndMouseHotplug(hid_loaded);
+#endif
+        WaitForSingleObject(s_HotplugEvent, INFINITE);
+    } while (SDL_GetAtomicInt(&s_HotplugRunning));
+
+    if (hid_loaded) {
+        WIN_UnloadHIDDLL();
+    }
+    return 0;
+}
 
 static DWORD CALLBACK SDL_DeviceNotificationFunc(HCMNOTIFICATION hNotify, PVOID context, CM_NOTIFY_ACTION action, PCM_NOTIFY_EVENT_DATA eventData, DWORD event_data_size)
 {
     if (action == CM_NOTIFY_ACTION_DEVICEINTERFACEARRIVAL ||
         action == CM_NOTIFY_ACTION_DEVICEINTERFACEREMOVAL) {
         s_LastDeviceNotification = SDL_GetTicksNS();
+        SetEvent(s_HotplugEvent);
     }
     return ERROR_SUCCESS;
 }
@@ -192,6 +219,11 @@ void WIN_InitDeviceNotification(void)
         return;
     }
 
+    // Start the device hotplug thread
+    SDL_SetAtomicInt(&s_HotplugRunning, true);
+    s_HotplugEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
+    s_HotplugThread = SDL_CreateThread(DeviceHotplugThread, "DeviceHotplugThread", NULL);
+
     cfgmgr32_lib_handle = LoadLibraryA("cfgmgr32.dll");
     if (cfgmgr32_lib_handle) {
         CM_Register_Notification = (CM_Register_NotificationFunc)GetProcAddress(cfgmgr32_lib_handle, "CM_Register_Notification");
@@ -225,6 +257,12 @@ void WIN_QuitDeviceNotification(void)
     // Make sure we have balanced calls to init/quit
     SDL_assert(s_DeviceNotificationsRequested == 0);
 
+    // Stop the device hotplug thread
+    SDL_SetAtomicInt(&s_HotplugRunning, false);
+    SetEvent(s_HotplugEvent);
+    SDL_WaitThread(s_HotplugThread, NULL);
+    s_HotplugThread = NULL;
+
     if (cfgmgr32_lib_handle) {
         if (s_DeviceNotificationFuncHandle && CM_Unregister_Notification) {
             CM_Unregister_Notification(s_DeviceNotificationFuncHandle);

src/video/windows/SDL_windowsevents.c

@@ -852,8 +852,6 @@ void WIN_PollRawInput(SDL_VideoDevice *_this, Uint64 poll_start)
     data->last_rawinput_poll = poll_finish;
 }
 
-#endif // !defined(SDL_PLATFORM_XBOXONE) && !defined(SDL_PLATFORM_XBOXSERIES)
-
 static void AddDeviceID(Uint32 deviceID, Uint32 **list, int *count)
 {
     int new_count = (*count + 1);
@@ -878,7 +876,6 @@ static bool HasDeviceID(Uint32 deviceID, const Uint32 *list, int count)
     return false;
 }
 
-#if !defined(SDL_PLATFORM_XBOXONE) && !defined(SDL_PLATFORM_XBOXSERIES)
 static char *GetDeviceName(HANDLE hDevice, HDEVINFO devinfo, const char *instance, Uint16 vendor, Uint16 product, const char *default_name, bool hid_loaded)
 {
     char *vendor_name = NULL;
@@ -964,8 +961,9 @@ static char *GetDeviceName(HANDLE hDevice, HDEVINFO devinfo, const char *instanc
     return name;
 }
 
-void WIN_CheckKeyboardAndMouseHotplug(SDL_VideoDevice *_this, bool initial_check)
+void WIN_CheckKeyboardAndMouseHotplug(bool hid_loaded)
 {
+    SDL_VideoDevice *_this = SDL_GetVideoDevice();
     PRAWINPUTDEVICELIST raw_devices = NULL;
     UINT raw_device_count = 0;
     int old_keyboard_count = 0;
@@ -977,18 +975,13 @@ void WIN_CheckKeyboardAndMouseHotplug(SDL_VideoDevice *_this, bool initial_check
     int new_mouse_count = 0;
     SDL_MouseID *new_mice = NULL;
 
-    if (!_this->internal->detect_device_hotplug) {
+    if (!_this ||
+        SDL_strcmp(_this->name, "windows") != 0 ||
+        !_this->internal->detect_device_hotplug ||
+        _this->internal->gameinput_context) {
         return;
     }
 
-    // Check to see if anything has changed
-    static Uint64 s_last_device_change;
-    Uint64 last_device_change = WIN_GetLastDeviceNotification();
-    if (!initial_check && last_device_change == s_last_device_change) {
-        return;
-    }
-    s_last_device_change = last_device_change;
-
     if ((GetRawInputDeviceList(NULL, &raw_device_count, sizeof(RAWINPUTDEVICELIST)) == -1) || (!raw_device_count)) {
         return; // oh well.
     }
@@ -1010,7 +1003,6 @@ void WIN_CheckKeyboardAndMouseHotplug(SDL_VideoDevice *_this, bool initial_check
     old_keyboards = SDL_GetKeyboards(&old_keyboard_count);
     old_mice = SDL_GetMice(&old_mouse_count);
 
-    bool hid_loaded = WIN_LoadHIDDLL();
     for (UINT i = 0; i < raw_device_count; i++) {
         RID_DEVICE_INFO rdi;
         char devName[MAX_PATH] = { 0 };
@@ -1077,9 +1069,6 @@ void WIN_CheckKeyboardAndMouseHotplug(SDL_VideoDevice *_this, bool initial_check
             break;
         }
     }
-    if (hid_loaded) {
-        WIN_UnloadHIDDLL();
-    }
 
     for (int i = old_keyboard_count; i--;) {
         if (!HasDeviceID(old_keyboards[i], new_keyboards, new_keyboard_count)) {
@@ -2718,10 +2707,6 @@ void WIN_PumpEvents(SDL_VideoDevice *_this)
         }
     }
 
-    if (!_this->internal->gameinput_context) {
-        WIN_CheckKeyboardAndMouseHotplug(_this, false);
-    }
-
     WIN_UpdateIMECandidates(_this);
 
 #endif // !defined(SDL_PLATFORM_XBOXONE) && !defined(SDL_PLATFORM_XBOXSERIES)

src/video/windows/SDL_windowsevents.h

@@ -30,7 +30,6 @@ extern HINSTANCE SDL_Instance;
 extern LRESULT CALLBACK WIN_KeyboardHookProc(int nCode, WPARAM wParam, LPARAM lParam);
 extern LRESULT CALLBACK WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
 extern void WIN_PollRawInput(SDL_VideoDevice *_this, Uint64 poll_start);
-extern void WIN_CheckKeyboardAndMouseHotplug(SDL_VideoDevice *_this, bool initial_check);
 extern void WIN_PumpEvents(SDL_VideoDevice *_this);
 extern void WIN_PumpEventsForHWND(SDL_VideoDevice *_this, HWND hwnd);
 extern void WIN_SendWakeupEvent(SDL_VideoDevice *_this, SDL_Window *window);

src/video/windows/SDL_windowsvideo.c

@@ -636,9 +636,6 @@ static bool WIN_VideoInit(SDL_VideoDevice *_this)
     WIN_InitKeyboard(_this);
     WIN_InitMouse(_this);
     WIN_InitDeviceNotification();
-    if (!_this->internal->gameinput_context) {
-        WIN_CheckKeyboardAndMouseHotplug(_this, true);
-    }
 #endif
 
     SDL_AddHintCallback(SDL_HINT_WINDOWS_RAW_KEYBOARD, UpdateWindowsRawKeyboard, _this);