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% BEGIN semlayer.doc
%%
\def\fileversion{1.0}
\def\filedate{93/04/01}
%%
%% LaTeX style option `semlayer.sty'.
%% For use with LaTeX v2.09 and the `seminar' document style.
%%
%% COPYRIGHT 1993, by Timothy Van Zandt, Timothy.VAN-ZANDT@insead.edu
%%
%% This file may be distributed and/or modified under the conditions of
%% the LaTeX Project Public License, either version 1.2 of this license
%% or (at your option) any later version. The latest version of this
%% license is in:
%%
%% http://www.latex-project.org/lppl.txt
%%
%% and version 1.2 or later is part of all distributions of LaTeX version
%% 1999/12/01 or later.
%%
%%
% **************************************************************************
% This is `semlayer.doc', which contains the documented code for
% `semlayer.sty'. You can use it in this form as the input file
% `semlayer.sty'. You can also create a stripped input file using
% sem-make.tex. You can print the documented code using sem-code.tex.
% sem-make.tex and sem-code.tex are distributed with seminar.sty.
% **************************************************************************
%
% \EndDocPreamble
%
% \CheckSum{276}
% \CharacterTable
% {Upper-case \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
% Lower-case \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
% Digits \0\1\2\3\4\5\6\7\8\9
% Exclamation \! Double quote \" Hash (number) \#
% Dollar \$ Percent \% Ampersand \&
% Acute accent \' Left paren \( Right paren \)
% Asterisk \* Plus \+ Comma \,
% Minus \- Point \. Solidus \/
% Colon \: Semicolon \; Less than \<
% Equals \= Greater than \> Question mark \?
% Commercial at \@ Left bracket \[ Backslash \\
% Right bracket \] Circumflex \^ Underscore \_
% Grave accent \` Left brace \{ Vertical bar \|
% Right brace \} Tilde \~}
%
%
% \section{Overlays}
%
% The main thing that the "\process@slide" macro does is successively send the
% main slide and then each overlay and layer to a slide output routine. In
% order to make the definition of that macro easier to understand, we first
% set up the overlays interface.
%
% Overlays must be implemented by some extra macros, such as in
% "semcolor.sty". Specifically, the commands "\@overlay" and "\make@overlay"
% should be defined.
%
% The reason for including the interface in "seminar.sty" is to encourage
% those who implement overlays to use a uniform interface, and to illustrate
% how overlays work. To be honest, though, it may not be possible to implement
% overlays without PostScript or a graphics language with similar capabilities
% using the interface that is defined here and without rewriting the basic
% slides macros.
%
% This system of overlays is so good and the system using invisible fonts is
% so lousy, that no special provisions have been made for supporting the
% latter. Actually, overlay should (and could easily) be implemented as \TeX{}
% primitives, saving everyone a lot of trouble.
%
% The system for overlays is not explained here in great detail. See
% "semcolor.sty" and "pstricks.tex" for an example of how overlays can be
% implemented.
%
% \begin{macrocode}
\addto@hook\before@newslide{%
\global\def\overlay@list{}%
\setcounter{overlay}{0}}
% \end{macrocode}
%
% \begin{macro}{\process@slide,\overlay@loop,\layer@loop}
% "\process@slide" is the beginning of the ``output'' routine for slides.
% "\@slidebox" is copied to "\@@slidebox". The "\make@overlay#1" macro should
% set "\@slidebox" to the contents of "\@@slidebox", but with only the
% material for overlay "#1" visible.
% \begin{macrocode}
\newbox\@@slidebox
\def\process@@slide{%
\ifx\overlay@list\@empty
\finish@slide
\output@slide
\else
\setbox\@@slidebox\box\@slidebox
\make@overlay{0}%
\finish@slide
\output@slide
{\let\theoverlay\theslide\layer@loop{0}}%
\overlay@loop
\fi}
\def\overlay@loop{%
\begingroup
\overlay@prep
\c@overlay=1
\@whilenum\c@overlay<10
\do{%
\test@member{\the\c@overlay}{\overlay@list}%
\if@test
\make@overlay{\the\c@overlay}%
\finish@slide
\output@slide
\fi
\layer@loop{\the\c@overlay}%
\advance\c@overlay by 1}%
\endgroup}
\def\layer@loop#1{%
\begingroup
\layer@prep
\@for\currlayer:=\layer@list\do{%
\test@member{#1-\currlayer}{\overlay@list}%
\if@test
\make@overlay{#1-\currlayer}%
\finish@slide
\output@slide
\fi}%
\endgroup}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\layer@prep,\overlay@prep}
% \begin{macrocode}
\def\layer@prep{%
\ifarticle\pagestyle{\layer@pagestyle}\fi
\let\thepage\thelayer
\ifx\thelayerframe\@empty\else\let\theslideframe\thelayerframe\fi
\let\slidelabel\layerlabel}
\def\overlay@prep{%
\ifarticle\pagestyle{\overlay@pagestyle}\fi
\let\thepage\theoverlay
\ifx\theoverlayframe\@empty\else\let\theslideframe\theoverlayframe\fi
\let\slidelabel\overlaylabel}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\layerframe,\overlayframe}
% \begin{macrocode}
\def\layerframe{\@slideframe{layer}}
\def\overlayframe{\@slideframe{overlay}}
\def\thelayerframe{}
\def\theoverlayframe{}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\overlaylabel,\layerlabel}
% \begin{macrocode}
\def\overlaylabel{\bf Overlay \theoverlay}
\def\layerlabel{\bf Layer \thelayer}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\theoverlay,\thelayer}
% \begin{macrocode}
\newcounter{overlay}
\def\theoverlay{\theslide-\alph{overlay}}
\def\currlayer{}
\def\thelayer{\theoverlay-\currlayer}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ifoverlays,\iflayers}
% Overlays and layers can be turned on and off independently.
% \begin{macrocode}
\newif\ifoverlays
\newif\iflayers
\@ifundefined{@overlay}%
{\let\@overlay\relax}%
{\ifarticle\else\overlaystrue\layerstrue\fi}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\nooverlays@err,\@overlay}
% "\@overlay" is set to "\relax" if it is not defined, for easy error
% detection.
% \begin{macrocode}
\def\nooverlays@err{%
\@seminarerr{You need to use additional macros for overlays,
e.g., semcolor.sty}\@ehd
\global\overlaysfalse
\global\layersfalse}
\@ifundefined{@overlay}{}{}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\overlay}
% The "\overlay" command starts by checking that the argument is a number
% between 0 and 9. If so, "\@overlay" is invoked. Except for overlay 0, the
% counter for cross-references is set to "overlay", and its value is set to
% the argument of "\overlay".
% \begin{macrocode}
\def\overlay#1{%
\ifoverlays\ifx\@overlay\relax\nooverlays@err\fi\fi
\ifslide
\@tempcnta=#1
\@testfalse
\ifnum\@tempcnta>-1 \ifnum\@tempcnta<10 \@testtrue\fi\fi
\if@test
\c@overlay=\@tempcnta
\ifnum\c@overlay=0
\advance\c@slide by -1
\refstepcounter{slide}%
\else
\advance\c@overlay by -1
\refstepcounter{overlay}%
\ifoverlays
\xdef\overlay@list{\overlay@list,\the\c@overlay}%
\fi
\fi
\ifoverlays
\@overlay{\the\c@overlay}%
\fi
\else
\@seminarerr{\string\overlay\space argument must be
an integer between 0 and 9}\@eha
\fi
\else
\@seminarerr{\string\overlay\space can only be used
in slide environments}\@eha
\fi
\ignorespaces}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\colorlayers}
% Color layers use the same mechanism as overlays; only the interface differs.
% \begin{macrocode}
\def\colorlayers#1{%
\edef\@tempc{#1}%
\edef\layer@list{\layer@list,#1}%
\def\@tempa##1{%
\@namedef{##1}{%
\iflayers\ifx\@overlay\relax\nooverlays@err\fi\fi
\ifslide
\iflayers
\xdef\overlay@list{\overlay@list,\the\c@overlay-##1}%
\@overlay{\the\c@overlay-##1}%
\fi
\else
\@seminarerr{Color layer `##1' can only be used in
slide environments}\@eha
\fi}}
\@for\@tempb:=\@tempc\do{%
\expandafter\@tempa\expandafter{\@tempb}}}
\def\layer@list{}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\layerpagestyle,\overlaypagestyle}
% \begin{macrocode}
\def\overlaypagestyle#1{\@ifgoodps{#1}{\edef\overlay@pagestyle{#1}}}
\def\layerpagestyle#1{\@ifgoodps{#1}{\edef\layer@pagestyle{#1}}}
\overlaypagestyle{}
\layerpagestyle{}
% \end{macrocode}
% \end{macro}
%
\endinput
% END semlayer.doc
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