scroll window fix

[Aric Stewart]

finds the case where the scrolling amount exceeds the window but still falls
within the clipping rect. This generates an additional update region 
that needs
to be invalidated.
includes a test
---
  dlls/user32/painting.c  |   21 +++++++++++++++++++++
  dlls/user32/tests/win.c |    9 +++++++++
  2 files changed, 30 insertions(+), 0 deletions(-)
-------------- next part --------------
diff --git a/dlls/user32/painting.c b/dlls/user32/painting.c
index dbc8cfe..8a613cf 100644
--- a/dlls/user32/painting.c
+++ b/dlls/user32/painting.c
@@ -870,6 +870,27 @@ INT WINAPI ScrollWindowEx( HWND hwnd, IN
                 CombineRgn( hrgnWinupd, hrgnWinupd, hrgnTemp, RGN_OR );
             RedrawWindow( hwnd, NULL, hrgnTemp, rdw_flags);
             DeleteObject( hrgnClip );
+
+	    /* Catch the case where the scolling amount exceeds the size of the
+	     * original window. This generated a second update area that is the
+	     * location where the original scrolled content would end up.
+	     * This second region is not returned by the ScrollDC and sets
+	     * ScrollWindowEx apart from just a ScrollDC.
+	     * 
+	     * This has been verified with testing on windows. 
+	     */
+	    if (abs(dx) > abs(rc.right - rc.left) ||
+			    abs(dy) > abs(rc.bottom - rc.top))
+	    {
+        	DeleteObject( hrgnTemp );
+		hrgnTemp = CreateRectRgn(rc.left + dx,  rc.top + dy, rc.right+dx, rc.bottom + dy);
+		CombineRgn( hrgnTemp, hrgnTemp, hrgnClip, RGN_AND );
+		CombineRgn( hrgnUpdate, hrgnUpdate, hrgnTemp, RGN_OR );
+
+		if( !bOwnRgn)
+			CombineRgn( hrgnWinupd, hrgnWinupd, hrgnTemp, RGN_OR );
+	    }
+
         }
         DeleteObject( hrgnTemp );
     } else {
diff --git a/dlls/user32/tests/win.c b/dlls/user32/tests/win.c
index 951c6aa..cade032 100644
--- a/dlls/user32/tests/win.c
+++ b/dlls/user32/tests/win.c
@@ -2991,6 +2991,15 @@ static void test_scrollvalidate( HWND pa
     CombineRgn( exprgn, exprgn, tmprgn, RGN_OR);
     ok( EqualRgn( exprgn, hrgn), "wrong update region\n");
 
+    SetRect( &rc, 0,40, 100,60);
+    SetRect( &cliprc, 0,0, 100,100);
+    ScrollWindowEx( hwnd1, 0, -25, &rc, &cliprc, hrgn, &rcu, SW_INVALIDATE);
+    SetRectRgn( tmprgn, 0,15,98,35);
+    CombineRgn( exprgn, exprgn, tmprgn, RGN_OR);
+    SetRectRgn( tmprgn, 0, 40, 98, 60);
+    CombineRgn( exprgn, exprgn, tmprgn, RGN_OR);
+    ok( EqualRgn( exprgn, hrgn), "wrong update region in excessive scroll\n");
+    
     /* now test ScrollWindowEx with a combination of
      * WS_CLIPCHILDREN style and SW_SCROLLCHILDREN flag */
     /* make hwnd2 the child of hwnd1 */