win32u: Introduce get_desktop_window.

dlls/win32u/class.c

@@ -285,7 +285,7 @@ ATOM WINAPI NtUserRegisterClassExWOW( const WNDCLASSEXW *wc, UNICODE_STRING *nam
     BOOL ret;
 
     /* create the desktop window to trigger builtin class registration */
-    if (!is_builtin && user_callbacks) user_callbacks->pGetDesktopWindow();
+    if (!is_builtin) get_desktop_window();
 
     if (wc->cbSize != sizeof(*wc) || wc->cbClsExtra < 0 || wc->cbWndExtra < 0 ||
         (!is_builtin && wc->hInstance == user32_module))  /* we can't register a class for user32 */
@@ -383,8 +383,8 @@ BOOL WINAPI NtUserUnregisterClass( UNICODE_STRING *name, HINSTANCE instance,
 {
     CLASS *class = NULL;
 
-    if (user_callbacks) /* create the desktop window to trigger builtin class registration */
-        user_callbacks->pGetDesktopWindow();
+    /* create the desktop window to trigger builtin class registration */
+    get_desktop_window();
 
     SERVER_START_REQ( destroy_class )
     {
@@ -423,7 +423,7 @@ ATOM WINAPI NtUserGetClassInfoEx( HINSTANCE instance, UNICODE_STRING *name, WNDC
     if (name->Buffer != (const WCHAR *)DESKTOP_CLASS_ATOM &&
         (IS_INTRESOURCE(name->Buffer) || name->Length != sizeof(messageW) ||
          wcsnicmp( name->Buffer, messageW, ARRAYSIZE(messageW) )))
-        user_callbacks->pGetDesktopWindow();
+        get_desktop_window();
 
     if (!(class = find_class( instance, name ))) return 0;
 

dlls/win32u/driver.c

@@ -64,8 +64,7 @@ const struct gdi_dc_funcs *get_display_driver(void)
 {
     if (user_driver == &lazy_load_driver)
     {
-        if (!user_callbacks || !user_callbacks->pGetDesktopWindow() ||
-            user_driver == &lazy_load_driver)
+        if (!get_desktop_window() || user_driver == &lazy_load_driver)
         {
             static struct user_driver_funcs empty_funcs;
             WARN( "failed to load the display driver, falling back to null driver\n" );

dlls/win32u/win32u_private.h

@@ -298,6 +298,7 @@ extern void user_check_not_lock(void) DECLSPEC_HIDDEN;
 
 /* window.c */
 struct tagWND;
+extern HWND get_desktop_window(void) DECLSPEC_HIDDEN;
 extern HWND is_current_thread_window( HWND hwnd ) DECLSPEC_HIDDEN;
 extern void flush_window_surfaces( BOOL idle ) DECLSPEC_HIDDEN;
 extern DWORD get_window_long( HWND hwnd, INT offset ) DECLSPEC_HIDDEN;

dlls/win32u/window.c

@@ -163,8 +163,7 @@ static HWND get_hwnd_message_parent(void)
 {
     struct user_thread_info *thread_info = get_user_thread_info();
 
-    if (!thread_info->msg_window && user_callbacks)
-        user_callbacks->pGetDesktopWindow();  /* trigger creation */
+    if (!thread_info->msg_window) get_desktop_window(); /* trigger creation */
     return thread_info->msg_window;
 }
 
@@ -186,8 +185,7 @@ static HWND get_full_window_handle( HWND hwnd )
 
     if (win == WND_DESKTOP)
     {
-        if (user_callbacks && LOWORD(hwnd) == LOWORD(user_callbacks->pGetDesktopWindow()))
-            return user_callbacks->pGetDesktopWindow();
+        if (LOWORD(hwnd) == LOWORD(get_desktop_window())) return get_desktop_window();
         else return get_hwnd_message_parent();
     }
 
@@ -619,7 +617,7 @@ static BOOL is_window_visible( HWND hwnd )
     {
         for (i = 0; list[i+1]; i++)
             if (!(get_window_long( list[i], GWL_STYLE ) & WS_VISIBLE)) break;
-        retval = !list[i+1] && (list[i] == user_callbacks->pGetDesktopWindow());  /* top message window isn't visible */
+        retval = !list[i+1] && (list[i] == get_desktop_window());  /* top message window isn't visible */
     }
     free( list );
     return retval;
@@ -648,7 +646,7 @@ static BOOL is_window_drawable( HWND hwnd, BOOL icon )
         for (i = 0; list[i+1]; i++)
             if ((get_window_long( list[i], GWL_STYLE ) & (WS_VISIBLE|WS_MINIMIZE)) != WS_VISIBLE)
                 break;
-        retval = !list[i+1] && (list[i] == user_callbacks->pGetDesktopWindow());  /* top message window isn't visible */
+        retval = !list[i+1] && (list[i] == get_desktop_window());  /* top message window isn't visible */
     }
     free( list );
     return retval;
@@ -689,7 +687,7 @@ static LONG_PTR get_window_long_size( HWND hwnd, INT offset, UINT size, BOOL ans
     if (offset == GWLP_HWNDPARENT)
     {
         HWND parent = NtUserGetAncestor( hwnd, GA_PARENT );
-        if (user_callbacks && parent == user_callbacks->pGetDesktopWindow())
+        if (parent == get_desktop_window())
             parent = get_window_relative( hwnd, GW_OWNER );
         return (ULONG_PTR)parent;
     }
@@ -706,7 +704,7 @@ static LONG_PTR get_window_long_size( HWND hwnd, INT offset, UINT size, BOOL ans
         {
         case GWL_STYLE:
             retval = WS_POPUP | WS_CLIPSIBLINGS | WS_CLIPCHILDREN; /* message parent is not visible */
-            if (user_callbacks && get_full_window_handle( hwnd ) == user_callbacks->pGetDesktopWindow())
+            if (get_full_window_handle( hwnd ) == get_desktop_window())
                 retval |= WS_VISIBLE;
             return retval;
         case GWL_EXSTYLE:

dlls/win32u/winstation.c

@@ -388,6 +388,15 @@ BOOL WINAPI NtUserSetObjectInformation( HANDLE handle, INT index, void *info, DW
     return ret;
 }
 
+HWND get_desktop_window(void)
+{
+    struct user_thread_info *thread_info = get_user_thread_info();
+
+    if (thread_info->top_window) return thread_info->top_window;
+    if (!user_callbacks) return 0;
+    return user_callbacks->pGetDesktopWindow();
+}
+
 static HANDLE get_winstations_dir_handle(void)
 {
     char bufferA[64];