Overlays are mainly of interest for making slides, and the overlay macros
described in this section are mainly of interest to \TeX{} macro writers who
want to implement overlays in a slide macro package. For example, the
\LPack{seminar} package, a \LaTeX{} style for notes and slides, uses PSTricks to
implement overlays.
Overlays are made by creating an "`\Lcs{hbox}"' and then outputting the box several
times, printing different material in the box each time. The box is created by
the commands
\begin{lstlisting}
\psoverlaybox < stuff >\endpsoverlaybox
\end{lstlisting}
\LaTeX{} users can instead write:
\begin{lstlisting}
\begin{psoverlaybox} <stuff> \end{psoverlaybox}
\end{lstlisting}
The material for overlay \texttt{<number>} should go within the scope of the command
\Lcs{psoverlay}\Largb{number}
\texttt{<number>} can be any any number, after expansion. Anything not in the scope of any
\Lcs{psoverlay} command goes on overlay "`0"', and material within the scope of
\Lcs{psoverlay}\Largb{-1} goes on all the overlays. \Lcs{psoverlay}
commands can be nested and can be used in math mode.
The command
\Lcs{putoverlaybox}\Largb{number}
then prints overlay \texttt{<number>}.
%
Here is an example:
\begin{LTXexample}[pos=t]
\psoverlaybox
\psoverlay{-1}
\psframebox[framearc=.15,linewidth=1.5pt]{%
\psoverlay{0}
\parbox{3.5cm}{\raggedright
Foam Cups Damage Environment {\psoverlay{1} Less than
Paper Cups,} Study Says.}}
\endpsoverlaybox
