[PATCH v2 4/7] win32u: GetUpdateRect() should clip update rectangle to the window client area.

[Dmitry Timoshkov]

From: Dmitry Timoshkov

Signed-off-by: Dmitry Timoshkov 
---
 dlls/win32u/dce.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/dlls/win32u/dce.c b/dlls/win32u/dce.c
index 6ff79c7b13a..9572053aa55 100644
--- a/dlls/win32u/dce.c
+++ b/dlls/win32u/dce.c
@@ -1446,14 +1446,21 @@ BOOL WINAPI NtUserGetUpdateRect( HWND hwnd, RECT *rect, BOOL erase )

if (rect && NtGdiGetRgnBox( update_rgn, rect ) != NULLREGION)
     {
-        HDC hdc = NtUserGetDCEx( hwnd, 0, DCX_USESTYLE );
-        DWORD layout = NtGdiSetLayout( hdc, -1, 0 );  /* map_window_points mirrors already */
         UINT win_dpi = get_dpi_for_window( hwnd );
-        map_window_points( 0, hwnd, (POINT *)rect, 2, win_dpi );
-        *rect = map_dpi_rect( *rect, win_dpi, get_thread_dpi() );
-        NtGdiTransformPoints( hdc, (POINT *)rect, (POINT *)rect, 2, NtGdiDPtoLP );
-        NtGdiSetLayout( hdc, -1, layout );
-        NtUserReleaseDC( hwnd, hdc );
+        RECT client_rect;
+
+        get_window_rects( hwnd, COORDS_SCREEN, NULL, &client_rect, win_dpi );
+        if (intersect_rect( rect, rect, &client_rect))
+        {
+            HDC hdc = NtUserGetDCEx( hwnd, 0, DCX_USESTYLE );
+            DWORD layout = NtGdiSetLayout( hdc, -1, 0 );  /* map_window_points mirrors already */
+
+            map_window_points( 0, hwnd, (POINT *)rect, 2, win_dpi );
+            *rect = map_dpi_rect( *rect, win_dpi, get_thread_dpi() );
+            NtGdiTransformPoints( hdc, (POINT *)rect, (POINT *)rect, 2, NtGdiDPtoLP );
+            NtGdiSetLayout( hdc, -1, layout );
+            NtUserReleaseDC( hwnd, hdc );
+        }
     }
     need_erase = send_erase( hwnd, flags, update_rgn, NULL, NULL );