Re: \presentationstep

[David Munger <mungerd@users.sourceforge.net>]

Hi all,

Inspiring from Otared Kavian's code and Han's presentation styles with
support for steps, I cooked the following in order to solve the non
JavaScript version issue. I post it in case it could be useful to other
people.

This implementation supports an \{Only|From|Until}Step[n] syntax as well
as the simple \NextStep-style one.

Otared: Any comments or suggestions?

And here is an example of usage:

-------------------------------------------
\StartSteps[Slide Title]           % the title is passed to
                                   % the \Subject macro

\startitemize
\item Item 1
\OnlyStep[2]  {\item (oops!)}
\UntilStep[4] {\item Item 2*}
\FromStep[4]  {\item Item 2}
\stopitemize

\StopSteps
-------------------------------------------

And here is a mixed example:

-------------------------------------------
\StartSteps[Navier||Stokes equation]

\[
  \frac{D\vec u}{Dt} =
    \FromStep[2][reserve]{-{\red \frac1\rho \vec\nabla p}}
    \FromStep[3][reserve]{+\;{\green \vec g}}
    \FromStep[4][reserve]{+\;{\blue \frac1\rho \div S}}
\]

Momentum transport:	\NextStep
\item {\red   Pressure gradient}	\par\NextStep
\item {\green Gravity}                  \par\NextStep
\item {\blue  Stress (viscous, turbulent, Maxwell)}

\StopSteps
-------------------------------------------

And here's the code:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% steps for slides
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\unprotect

\newif\ifUseSteps
\UseStepstrue
% \UseStepsfalse


\long\def\StartSteps[#1]#2\StopSteps{%
  \let\steps@number\plusone%
  \let\steps@counter\plusone%
  \ifUseSteps%
    \loop%
      \let\steps@autocounter\zerocount%
      \Subject{#1}\par\steps@startstep#2\steps@stopstep%
      \steps@updatenumber\steps@autocounter%
    \ifnum\steps@counter<\steps@number%
      \increment\steps@counter%
    \repeat%
  \else%
    \Subject{#1}\par\steps@startstep#2\steps@stopstep%
  \fi}

\def\NextStep{\steps@stopstep\steps@startstep}

\def\OnlyStep[#1]{%
  \steps@updatenumber#1%
  \def\steps@cond{\steps@counter=#1}%
  \dosingleempty\steps@dostep}

\def\FromStep[#1]{%
  \steps@updatenumber#1%
  \let\steps@tmpcounter\zerocount%
  \increment(\steps@tmpcounter,#1-1)%
  \def\steps@cond{\steps@counter>\steps@tmpcounter}%
  \dosingleempty\steps@dostep}

\def\UntilStep[#1]{%
  \steps@updatenumber#1%
  \def\steps@cond{\steps@counter<#1}%
  \dosingleempty\steps@dostep}



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% internal macros
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\newcounter\steps@counter
\newcounter\steps@autocounter
\newcounter\steps@number
\newcounter\steps@tmpcounter

\def\steps@startstep{%
  \increment\steps@autocounter%
  \def\steps@hide{no}%
  \ifUseSteps%
    \ifnum\steps@autocounter>\steps@counter%
      \def\steps@hide{yes}%
    \fi%
  \fi%
  \starthidden}

\def\steps@stopstep{\stophidden}

\def\steps@updatenumber#1{\ifnum\steps@number<#1%
  \doglobal\let\steps@number\zerocount%
  \doglobal\increment(\steps@number,#1)\fi}

\defineframedtext
  [step@frame]
  [offset=overlay,width=broad,height=fit,frame=off]

\def\starthidden{\startstep@frame[empty=\steps@hide]}
\def\stophidden{\stopstep@frame}


\long\def\steps@dostep[#1]#2{%
  \processallactionsinset
    [#1]
    [	reserve=>\let\steps@next=\steps@dostepreserve,
	\s!default=>\let\steps@next=\steps@dostepnoreserve]
  \steps@next{#2}}

\long\def\steps@dostepreserve#1{%
  \def\steps@hide{no}%
  \ifUseSteps%
    \ifnum\steps@cond\else%
      \def\steps@hide{yes}%
    \fi%
  \fi%
  \ifmmode\expandafter\mframed\else\expandafter\framed\fi%
  [empty=\steps@hide,frame=off,offset=overlay]{#1}%
  \ifmmode\;\fi}

\long\def\steps@dostepnoreserve#1{%
  \def\steps@next{#1\ifmmode\;\fi}%
  \ifUseSteps%
    \ifnum\steps@cond\else\def\steps@next{\relax}\fi%
  \fi\steps@next}

\protect