note about logical ops and DrawText under Windows

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_2_BRANCH@7570 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/latex/wx/dc.tex

@@ -348,6 +348,11 @@ the string. See \helpref{wxDC::GetTextExtent}{wxdcgettextextent} for how
 to get the dimensions of a text string, which can be used to position the
 text more precisely.
 
+{\bf NB:} under wxGTK the current 
+\helpref{logical function}{wxdcgetlogicalfunction} is used by this function
+but it is ignored by wxMSW. Thus, you should avoid using logical functions
+with this function in portable programs.
+
 \membersection{wxDC::EndDoc}\label{wxdcenddoc}
 
 \func{void}{EndDoc}{\void}