Fix wxClientDC::Clear() for scrolled windows in wxMSW.

Take the DC origin into account when clearing a window DC and not only a
memory one.

Closes #2048.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@75730 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -617,6 +617,7 @@ wxMSW:
 - Fix coordinates of EVT_MOUSEWHEEL in frames with toolbars (LtJax).
 - Support "show" verb as well as "open" in wxFileType (Eric Jensen).
 - Fix display of bitmaps with alpha in wxStaticBitmap (Artur Wieczorek).
+- Fix wxClientDC::Clear() for scrolled windows (Artur Wieczorek).
 - Make wxPrinterDC::DrawIcon() actually work (Artur Wieczorek).
 
 wxOSX:

src/msw/dc.cpp

@@ -694,11 +694,13 @@ void wxMSWDCImpl::Clear()
         if (!m_selectedBitmap.IsOk())
             return;
 
-        rect.left = -m_deviceOriginX; rect.top = -m_deviceOriginY;
-        rect.right = m_selectedBitmap.GetWidth()-m_deviceOriginX;
-        rect.bottom = m_selectedBitmap.GetHeight()-m_deviceOriginY;
+        rect.left = rect.top = 0;
+        rect.right = m_selectedBitmap.GetWidth();
+        rect.bottom = m_selectedBitmap.GetHeight();
     }
 
+    ::OffsetRect(&rect, -m_deviceOriginX, -m_deviceOriginY);
+
 #ifndef __WXWINCE__
     (void) ::SetMapMode(GetHdc(), MM_TEXT);
 #endif