Re: \presentationstep

[Otared Kavian <otared@wanadoo.fr>]

At 16:10 -0500 8/11/04, David Munger wrote:
>
>Argh... It's because of the line splits in email. I just put the file on
>my website:
>
>http://cfd.homelinux.org/tex/
>

Hi David and all ConTeXters,

I was away from my e-mail so I am late in answering.
Thank you for the file you put on your site. Indeed everything works 
as intended (the \placeformula no longer advances with each step), 
and I think one may suggest to Hans to include this in future 
distributions.

However, in the spirit of ConTeXters who are always asking for a 
step(!) towards perfectness, I let you know the following drawbacks 
of the macros:

1) Somehow the \FromStep[n][reserve] changes the internal mechanism 
of glue or spaces in displayed formulas. So one needs (as you do in 
your example) to add \; around operators such as +, -, =. Can one 
avoid this?

2) When one refers (see example below) with the command (\in[eq:NS]) 
to an equation which has been introduced with \placeformula[eq:NS] 
the interaction makes appear the first instance of that formula, 
which may be incomplete. Could one have a control over this, that is 
for instance, in this particular case, make appear the completed 
equation at the end of the slide made with \StartSteps[Navier||Stokes 
equation]?

Best regards: OK

%%%% file steps-david-3.tex
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% usage example
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\usemodule [pre-original]
\usemodule [rsteps]

\starttext
\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}
\HighlightStep[3]{\item
Here is another version of Navier-Stokes equation}
\stopitemize

\StopSteps


\StartSteps[Navier||Stokes equation]

\placeformula[eq:incompressibility]
\startformula
   \vec\nabla\cdot\vec u = 0
\stopformula

\placeformula[eq:NS]
\startformula
   \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 \vec\nabla\cdot S}}
\stopformula

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


\StopSteps

\StartSteps[Navier Stokes equation]


\placeformula[eq:div-nul]
\startformula
   \vec\nabla\cdot\vec u = 0
\stopformula


\placeformula[eq:NStokes]
\startformula
   { \partial u \over \partial t} - \Delta u
       \FromStep[1][reserve]{{\red  \; +\; (u\cdot \nabla)u}}
     \FromStep[2][reserve]{{\green \; +\;  \nabla p}}
     \FromStep[3][reserve]{{\blue \; =\;  f(t,x)}}
\stopformula

Comments:
\NextStep \item Nonlinear equation (same is true for equation 
(\in[eq:NS]) \par\NextStep
\item One should add initial conditions \par\NextStep
\item and boundary conditions

\StopSteps
\stoptext
%%%%%% end file steps-david-3.tex