server: Don't invalidate the newly exposed child region on the parent if it doesn't clip children.

dlls/user32/tests/msg.c

@@ -9302,8 +9302,6 @@ static void subtest_swp_paint_regions_( int line, int wrap_toplevel, LPCSTR pare
             }
             else
             {
-                todo_wine_if( !EqualRect( &rect_old, &rect_new ) &&
-                              (extest->style & WS_CLIPCHILDREN) == 0 && !is_composited )
                 ok( !!rgn_ok, "Parent update region shall match expected region\n" );
             }
 
@@ -9365,8 +9363,6 @@ static void subtest_swp_paint_regions_( int line, int wrap_toplevel, LPCSTR pare
             }
             else
             {
-                todo_wine_if( !EqualRect( &rect_old, &rect_new ) &&
-                              (extest->style & WS_CLIPCHILDREN) == 0 && !is_composited )
                 ok( !!rgn_ok, "Child update region shall match expected region\n" );
             }
 

server/window.c

@@ -1766,10 +1766,8 @@ static struct region *expose_window( struct window *win, const rectangle_t *old_
         offset_region( new_vis_rgn, win->window_rect.left - old_window_rect->left,
                        win->window_rect.top - old_window_rect->top  );
 
-        if (is_composited ? union_region( new_vis_rgn, old_vis_rgn, new_vis_rgn ) :
-            (win->parent->style & WS_CLIPCHILDREN) ?
-            subtract_region( new_vis_rgn, old_vis_rgn, new_vis_rgn ) :
-            xor_region( new_vis_rgn, old_vis_rgn, new_vis_rgn ))
+        if (is_composited ? union_region( new_vis_rgn, old_vis_rgn, new_vis_rgn )
+                          : subtract_region( new_vis_rgn, old_vis_rgn, new_vis_rgn ))
         {
             if (!is_region_empty( new_vis_rgn ))
             {