dc.SetPen(m_penBlack);
+#ifdef __WXMAC__
+ dc.SetLogicalFunction(wxCOPY);
+#else
// this seems to be closer than what Windows does than wxINVERT although
// I'm still not sure if it's correct
dc.SetLogicalFunction(wxAND_REVERSE);
+#endif
wxCoord z;
for ( z = x1 + 1; z < x2; z += 2 )