Make sure we don't call the graphics driver after process detach.

dlls/user/driver.c

@@ -137,6 +137,13 @@ static const USER_DRIVER *load_driver(void)
     return driver;
 }
 
+/* unload the graphics driver on process exit */
+void USER_unload_driver(void)
+{
+    /* make sure we don't try to call the driver after it has been detached */
+    USER_Driver = &null_driver;
+}
+
 
 /**********************************************************************
  * Null user driver

dlls/user/user_main.c

@@ -228,6 +228,9 @@ BOOL WINAPI DllMain( HINSTANCE inst, DWORD reason, LPVOID reserved )
     case DLL_THREAD_DETACH:
         thread_detach();
         break;
+    case DLL_PROCESS_DETACH:
+        USER_unload_driver();
+        break;
     }
     return ret;
 }

dlls/user/user_private.h

@@ -159,6 +159,8 @@ typedef struct tagUSER_DRIVER {
 
 extern const USER_DRIVER *USER_Driver;
 
+extern void USER_unload_driver(void);
+
 struct received_message_info;
 struct hook16_queue_info;