From c5effe4953e557ef5ad8cfcddf2a4edb68e151df Mon Sep 17 00:00:00 2001
From: Vadim Zeitlin <vadim@wxwidgets.org>
Date: Mon, 5 Mar 2007 08:58:09 +0000
Subject: [PATCH] use virtual size for the size of the buffer when
 wxBUFFER_VIRTUAL_AREA style is used [backport from HEAD]

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@44609 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
---
 include/wx/dcbuffer.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/wx/dcbuffer.h b/include/wx/dcbuffer.h
index ef5383bbdf..0f4e896d9f 100644
--- a/include/wx/dcbuffer.h
+++ b/include/wx/dcbuffer.h
@@ -173,7 +173,7 @@ public:
         if( buffer.IsOk() )
             Init(&m_paintdc, buffer, style);
         else
-            Init(&m_paintdc, window->GetClientSize(), style);
+            Init(&m_paintdc, GetBufferedSize(window, style), style);
     }
 
     // If no bitmap is supplied by the user, a temporary one will be created.
@@ -184,7 +184,7 @@ public:
         if (style & wxBUFFER_VIRTUAL_AREA)
             window->PrepareDC( m_paintdc );
 
-        Init(&m_paintdc, window->GetClientSize(), style);
+        Init(&m_paintdc, GetBufferedSize(window, style), style);
     }
 
     // default copy ctor ok.
@@ -196,6 +196,15 @@ public:
         UnMask();
     }
 
+protected:
+    // return the size needed by the buffer: this depends on whether we're
+    // buffering just the currently shown part or the total (scrolled) window
+    static wxSize GetBufferedSize(wxWindow *window, int style)
+    {
+        return style & wxBUFFER_VIRTUAL_AREA ? window->GetVirtualSize()
+                                             : window->GetClientSize();
+    }
+
 private:
     wxPaintDC m_paintdc;