From bc623d1af6774b4b557bffe2a53adac5c273db92 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Mon, 16 Feb 2026 10:35:38 -0800
Subject: [PATCH] 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 | 38 +++++++++++++++++++++++++++
src/video/windows/SDL_windowsevents.c | 27 +++++--------------
src/video/windows/SDL_windowsevents.h | 1 -
src/video/windows/SDL_windowsvideo.c | 3 ---
4 files changed, 44 insertions(+), 25 deletions(-)
diff --git a/src/core/windows/SDL_hid.c b/src/core/windows/SDL_hid.c
index f4bd5cef95264..1f629d58d2174 100644
--- a/src/core/windows/SDL_hid.c
+++ b/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);
diff --git a/src/video/windows/SDL_windowsevents.c b/src/video/windows/SDL_windowsevents.c
index 1155ba59c9841..3e9be16b92050 100644
--- a/src/video/windows/SDL_windowsevents.c
+++ b/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)
diff --git a/src/video/windows/SDL_windowsevents.h b/src/video/windows/SDL_windowsevents.h
index d49518b8f75d9..45f5527dc658c 100644
--- a/src/video/windows/SDL_windowsevents.h
+++ b/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);
diff --git a/src/video/windows/SDL_windowsvideo.c b/src/video/windows/SDL_windowsvideo.c
index b7e4991bee413..056a69883acf9 100644
--- a/src/video/windows/SDL_windowsvideo.c
+++ b/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);