From 10d038e43f5f339bae967db5c6c88f4a05153feb Mon Sep 17 00:00:00 2001
From: Megamouse <studienricky89@googlemail.com>
Date: Fri, 24 Jan 2025 19:01:16 +0100
Subject: [PATCH] Qt: Fix device notification registration segfault

The main window does not exist if we boot with no-gui
---
 rpcs3/rpcs3qt/gui_application.cpp | 69 ++++++++++++++++++++++++-------
 rpcs3/rpcs3qt/gui_application.h   |  4 ++
 2 files changed, 59 insertions(+), 14 deletions(-)

diff --git a/rpcs3/rpcs3qt/gui_application.cpp b/rpcs3/rpcs3qt/gui_application.cpp
index e25c0627f4..7c01333540 100644
--- a/rpcs3/rpcs3qt/gui_application.cpp
+++ b/rpcs3/rpcs3qt/gui_application.cpp
@@ -76,10 +76,7 @@ gui_application::~gui_application()
 	discord::shutdown();
 #endif
 #ifdef _WIN32
-	if (m_device_notification_handle && !UnregisterDeviceNotification(m_device_notification_handle))
-	{
-		gui_log.error("UnregisterDeviceNotification() failed: %s", fmt::win_error{GetLastError(), nullptr});
-	}
+	unregister_device_notification();
 #endif
 }
 
@@ -205,17 +202,9 @@ bool gui_application::Init()
 #ifdef _WIN32 // Currently only needed for raw mouse input on windows
 	installNativeEventFilter(&m_native_event_filter);
 
-	// Enable usb device hotplug events
-	// Currently only needed for hotplug on windows, as libusb handles other platforms
-	DEV_BROADCAST_DEVICEINTERFACE notification_filter {};
-	notification_filter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
-	notification_filter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
-	notification_filter.dbcc_classguid = GUID_DEVINTERFACE_USB_DEVICE;
-
-	m_device_notification_handle = RegisterDeviceNotification(reinterpret_cast<HWND>(m_main_window->winId()), &notification_filter, DEVICE_NOTIFY_WINDOW_HANDLE);
-	if (!m_device_notification_handle )
+	if (m_main_window)
 	{
-		gui_log.error("RegisterDeviceNotification() failed: %s", fmt::win_error{GetLastError(), nullptr});
+		register_device_notification(m_main_window->winId());
 	}
 #endif
 
@@ -491,11 +480,26 @@ std::unique_ptr<gs_frame> gui_application::get_gs_frame()
 	}
 
 	m_game_window = frame;
+	ensure(m_game_window);
+
+#ifdef _WIN32
+	if (!m_show_gui)
+	{
+		register_device_notification(m_game_window->winId());
+	}
+#endif
 
 	connect(m_game_window, &gs_frame::destroyed, this, [this]()
 	{
 		gui_log.notice("gui_application: Deleting old game window");
 		m_game_window = nullptr;
+
+#ifdef _WIN32
+		if (!m_show_gui)
+		{
+			unregister_device_notification();
+		}
+#endif
 	});
 
 	return std::unique_ptr<gs_frame>(frame);
@@ -1234,3 +1238,40 @@ bool gui_application::native_event_filter::nativeEventFilter([[maybe_unused]] co
 
 	return false;
 }
+
+#ifdef _WIN32
+void gui_application::register_device_notification(WId window_id)
+{
+	if (m_device_notification_handle) return;
+
+	gui_log.notice("Registering device notifications...");
+
+	// Enable usb device hotplug events
+	// Currently only needed for hotplug on windows, as libusb handles other platforms
+	DEV_BROADCAST_DEVICEINTERFACE notification_filter {};
+	notification_filter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
+	notification_filter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
+	notification_filter.dbcc_classguid = GUID_DEVINTERFACE_USB_DEVICE;
+
+	m_device_notification_handle = RegisterDeviceNotification(reinterpret_cast<HWND>(window_id), &notification_filter, DEVICE_NOTIFY_WINDOW_HANDLE);
+	if (!m_device_notification_handle )
+	{
+		gui_log.error("RegisterDeviceNotification() failed: %s", fmt::win_error{GetLastError(), nullptr});
+	}
+}
+
+void gui_application::unregister_device_notification()
+{
+	if (m_device_notification_handle)
+	{
+		gui_log.notice("Unregistering device notifications...");
+
+		if (!UnregisterDeviceNotification(m_device_notification_handle))
+		{
+			gui_log.error("UnregisterDeviceNotification() failed: %s", fmt::win_error{GetLastError(), nullptr});
+		}
+
+		m_device_notification_handle = {};
+	}
+}
+#endif
diff --git a/rpcs3/rpcs3qt/gui_application.h b/rpcs3/rpcs3qt/gui_application.h
index f766c3b9c2..a09e7bb895 100644
--- a/rpcs3/rpcs3qt/gui_application.h
+++ b/rpcs3/rpcs3qt/gui_application.h
@@ -121,9 +121,13 @@ private:
 	u64 m_pause_delayed_tag = 0;
 	typename Emulator::stop_counter_t m_emu_focus_out_emulation_id{};
 	bool m_is_pause_on_focus_loss_active = false;
+
 #ifdef _WIN32
+	void register_device_notification(WId window_id);
+	void unregister_device_notification();
 	HDEVNOTIFY m_device_notification_handle {};
 #endif
+
 private Q_SLOTS:
 	void OnChangeStyleSheetRequest();
 	void OnShortcutChange();