From 1b6d127aee1210f8f9436b85bb34a9c416d0aaac Mon Sep 17 00:00:00 2001
From: Aric Stewart <aric@codeweavers.com>
Date: Tue, 13 Feb 2007 07:38:06 -0600
Subject: [PATCH] user32: Scroll window fix.

Fix 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.
---
 dlls/user32/painting.c  | 19 +++++++++++++++++++
 dlls/user32/tests/win.c |  9 +++++++++
 2 files changed, 28 insertions(+)

diff --git a/dlls/user32/painting.c b/dlls/user32/painting.c
index dbc8cfeb814..9fe6764344d 100644
--- a/dlls/user32/painting.c
+++ b/dlls/user32/painting.c
@@ -870,6 +870,25 @@ INT WINAPI ScrollWindowEx( HWND hwnd, INT dx, INT dy,
                 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))
+            {
+                SetRectRgn( hrgnTemp, 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 ef456cabe3e..9d07306bb1b 100644
--- a/dlls/user32/tests/win.c
+++ b/dlls/user32/tests/win.c
@@ -2991,6 +2991,15 @@ static void test_scrollvalidate( HWND parent)
     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 */