Introduce 'zOrder' to give control over drawing order

chapters/annotations.tex

@@ -236,6 +236,7 @@ \subsubsection{Plot Curves}\label{plot-curves}
   expression x = time "X coordinate values";
   expression y "Y coordinate values";
   String legend "Legend";
+  Integer zOrder = 0 "Drawing order control";
 end Curve;
 \end{lstlisting}
 
@@ -256,6 +257,9 @@ \subsubsection{Plot Curves}\label{plot-curves}
 Variable replacements, as described in \cref{variable-replacements}, can be used in \lstinline!legend!.
 The order of presentation within the plot legend corresponds to order of appearance in the \lstinline!curves! of a \lstinline!Plot!.
 
+The \lstinline!zOrder! gives control over drawing order, with higher values corresponding to closer to front.
+Ties are resolved using order of appearance in the \lstinline!curves! of a \lstinline!Plot!, with later appearance corresponding to closer to front.
+
 \subsubsection{Escape Sequences}\label{text-markup-escape-sequences}
 
 In an attribute inside a figure where the variable replacements of \cref{variable-replacements} or the text markup of \cref{text-markup-in-captions} can be used, the following use of \firstuse[text markup escape sequence]{text markup escape sequences}\index{escape sequence!text markup} applies.