user32: Use wait_graphics_driver_ready() in load_desktop_driver().

dlls/user32/driver.c

@@ -55,7 +55,7 @@ static BOOL load_desktop_driver( HWND hwnd, HMODULE *module )
     USER_CheckNotLock();
 
     strcpy( driver_load_error, "The explorer process failed to start." );  /* default error */
-    SendMessageW( hwnd, WM_NULL, 0, 0 );  /* wait for the desktop process to be ready */
+    wait_graphics_driver_ready();
 
     guid_atom = HandleToULong( GetPropW( hwnd, L"__wine_display_device_guid" ));
     lstrcpyW( key, L"System\\CurrentControlSet\\Control\\Video\\{" );

dlls/user32/sysparams.c

@@ -583,7 +583,7 @@ static void release_display_device_init_mutex( HANDLE mutex )
 }
 
 /* Wait until graphics driver is loaded by explorer */
-static void wait_graphics_driver_ready(void)
+void wait_graphics_driver_ready(void)
 {
     static BOOL ready = FALSE;
 

dlls/user32/user_private.h

@@ -258,6 +258,7 @@ extern void move_window_bits( HWND hwnd, struct window_surface *old_surface,
 extern void move_window_bits_parent( HWND hwnd, HWND parent, const RECT *window_rect,
                                      const RECT *valid_rects ) DECLSPEC_HIDDEN;
 extern void update_window_state( HWND hwnd ) DECLSPEC_HIDDEN;
+extern void wait_graphics_driver_ready(void) DECLSPEC_HIDDEN;
 extern void *get_hook_proc( void *proc, const WCHAR *module, HMODULE *free_module ) DECLSPEC_HIDDEN;
 extern RECT get_virtual_screen_rect(void) DECLSPEC_HIDDEN;
 extern LRESULT call_current_hook( HHOOK hhook, INT code, WPARAM wparam, LPARAM lparam ) DECLSPEC_HIDDEN;