Desktop window is repainted on WM_ERASEBKGND, it must never get a

dlls/user/painting.c

@@ -265,7 +265,7 @@ static BOOL send_erase( HWND hwnd, UINT flags, HRGN client_rgn,
             }
             if (!hdc_ret)
             {
-                if (need_erase)  /* FIXME: mark it as needing erase again */
+                if (need_erase && hwnd != GetDesktopWindow())  /* FIXME: mark it as needing erase again */
                     RedrawWindow( hwnd, NULL, client_rgn, RDW_INVALIDATE | RDW_ERASE | RDW_NOCHILDREN );
                 ReleaseDC( hwnd, hdc );
             }
@@ -282,7 +282,7 @@ static BOOL send_erase( HWND hwnd, UINT flags, HRGN client_rgn,
  *
  * Implementation of RDW_ERASENOW behavior.
  */
-void erase_now( HWND hwnd, UINT rdw_flags )
+static void erase_now( HWND hwnd, UINT rdw_flags )
 {
     HWND child;
     HRGN hrgn;
@@ -324,10 +324,13 @@ void erase_now( HWND hwnd, UINT rdw_flags )
  * HIWORD(lParam) = hwndSkip  (not used; always NULL)
  *
  */
-void update_now( HWND hwnd, UINT rdw_flags )
+static void update_now( HWND hwnd, UINT rdw_flags )
 {
     HWND child;
 
+    /* desktop window never gets WM_PAINT, only WM_ERASEBKGND */
+    if (hwnd == GetDesktopWindow()) erase_now( hwnd, rdw_flags | RDW_NOCHILDREN );
+
     /* loop while we find a child to repaint */
     for (;;)
     {

dlls/x11drv/desktop.c

@@ -44,8 +44,7 @@ static LRESULT WINAPI desktop_winproc( HWND hwnd, UINT message, WPARAM wParam, L
 
     case WM_ERASEBKGND:
         PaintDesktop( (HDC)wParam );
-        ValidateRect( hwnd, NULL );
-        break;
+        return TRUE;
 
     case WM_SYSCOMMAND:
         if ((wParam & 0xfff0) == SC_CLOSE) ExitWindows( 0, 0 );

server/window.c

@@ -1660,7 +1660,12 @@ DECL_HANDLER(get_update_region)
     else
     {
         if (reply->flags & UPDATE_NONCLIENT) validate_non_client( win );
-        if (reply->flags & UPDATE_ERASE) win->paint_flags &= ~PAINT_ERASE;
+        if (reply->flags & UPDATE_ERASE)
+        {
+            win->paint_flags &= ~PAINT_ERASE;
+            /* desktop window only gets erased, not repainted */
+            if (win == top_window) validate_whole_window( win );
+        }
     }
 }