patch for bounding box initialization

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_2_BRANCH@7487 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dc.h

@@ -48,6 +48,7 @@ public:
     {
         m_clipping = FALSE;
         m_ok = TRUE;
+        m_isBBoxValid = FALSE;
 
         m_minX = m_minY = m_maxX = m_maxY = 0;
 
@@ -399,12 +400,24 @@ public:
     // ------------
 
     virtual void CalcBoundingBox(wxCoord x, wxCoord y)
+    {
+      if ( m_isBBoxValid )
       {
          if ( x < m_minX ) m_minX = x;
          if ( y < m_minY ) m_minY = y;
          if ( x > m_maxX ) m_maxX = x;
          if ( y > m_maxY ) m_maxY = y;
       }
+      else
+      {
+         m_isBBoxValid = TRUE;
+
+         m_minX = x;
+         m_minY = y;
+         m_maxX = x;
+         m_maxY = y;
+      }
+    }
 
     // Get the final bounding box of the PostScript or Metafile picture.
     wxCoord MinX() const { return m_minX; }
@@ -577,6 +590,7 @@ protected:
     bool m_ok:1;
     bool m_clipping:1;
     bool m_isInteractive:1;
+    bool m_isBBoxValid:1;
 
     // coordinate system variables