\subsection{Tweaking the appearance of bonds}
\label{sec:tweaking}

The plain command 

\lstinputlisting{morphine.sh}

produces 

\cfpic{morphine.tex}

which can be improved. First, we may want to give the double (and, if present, triple) bonds a more well-proportioned look. To do so, use option \lstinline!--fancy-bonds! or \lstinline!-f!:

\lstinputlisting{morphine-f.sh}

which gives

\cfpic{morphine-f.tex}

Note that the look of the double bonds involves some \tkz trickery; in the generated code, the double bonds are no longer represented by \lstinline!=! symbols but instead by something like \lstinline!-[:120,,,,drh]!. 

Next, the molecule contains two bonds that cross each other, and we would like to draw the vertical one in the foreground. To specify this bond, we need the numbers of the adjoining atoms. We first can let \mcf print the atom numbers:

\lstinputlisting{morphine-n.sh}

which gives 

\cfpic{morphine-n.tex}

The bond that we are looking at connects atoms 19 and 20. We now can use the \lstinline!-k! or \lstinline!--crossbond! option to put it in the foreground:

\lstinputlisting{morphine-k.sh}

which gives us 

\cfpic{morphine-k.tex}

To draw crossing bonds, atom numbers and proportioned double or triple bonds, \mcf relies on several custom macros and \tkz styles defined in the \texttt{mol2chemfig.sty} package. Accordingly, the generated code becomes a bit more verbose and less \chf-like. 

