Re: does metafun require texexec --final?

[Sanjoy Mahajan <sanjoy@mrao.cam.ac.uk>]

[Hans: Feature suggestion for figure inclusion at the end...]

I wrote:
> So, is --final a requirement when using metafun, or am I hacking
> around a problem I've caused by leaving something out?

An answer is that I should set \runMPgraphicstrue.  I thought it was
automatically set, half-remembering what Aditya said in the previous
thread on metafun.  So the following works (changing the r changes the
result right away without requiring --final or requiring two texexec
runs):

========= cut here ==================
\runMPgraphicstrue
\starttext

\startreusableMPgraphic{a}
r := 1cm;
fill fullcircle scaled r;
\stopreusableMPgraphic

\placefigure[force,none]{}{\reuseMPgraphic{a}}

the figure above should be a small circle

\stoptext
========= cut here ==================

To see where and when \runMPgraphicstrue was done, I looked into the
metafun interface code, and asked grep for help:

$ grep '\\runMPgraphicstrue' *.tex
s-pre-02.tex:113:%D switch \type {\runMPgraphicstrue} to the local file \type
supp-mps.tex:1195:%D \runMPgraphicstrue
supp-mps.tex:1209:%D \type{\runMPgraphicstrue}, the \METAPOST\ scratch file
supp-mps.tex:1653:%D \global\runMPgraphicstrue
supp-mps.tex:1991:   \runMPgraphicstrue

So it's commented-in only at line 1991, which is part of a new (to me)
method of figure inclusion: \startstaticMPgraphic, which says
"Dedicated to Aditya Mahajan. See meta-ini for usage", so I see how
Aditya would conclude that \runMPgraphicstrue is always true :-)

The following therefore also works to get instant updating, and is
more efficient than reusable MP graphics in that it reruns metapost on
included figures only when they change:

========= cut here ==================
% no need to set \runMPgraphicstrue
\starttext

% see how smart staticMPfigure is by changing r here but not
% in the figure definition itself.  Will it re-metapost the graphic?
% Answer: It's smart.
\startMPinclusions
r := 1cm;
\stopMPinclusions

\startstaticMPfigure{a}
fill fullcircle scaled r;
\stopstaticMPfigure

\placefigure[force,none]{}{\usestaticMPfigure[a]}

the figure above should be a small or large circle

\stoptext
========= cut here ==================

Which I just now see is on the Wiki page about metafun (I'd been
working from the excellent metafun manual).

It's doubly smart in that changing the papersize (which changes the
layout parameters, which are included in the metapost file) will rerun
the graphic, even if r stays the same.  So the graphic can base itself
on those parameters and be updated when needed.

Thanks, Hans and Aditya!

While experimenting with the methods of figure inclusion, I've been
changing among \reuseMPgraphic, \usestaticMPfigure, \useMPgraphic, and
\externalfigure to call up the figure.  Do all the figure labels live
in the same namespace?  In which case (warning: feature suggestion!)
when they are defined, e.g. with \useexternalfigure,
\startstaticMPfigure, ..., could the label have associated with it the
command that calls it up?  So one could do for all types:

\usefigure[thelabel]

and ConTeXt would figure out what kind of figure it is and turn
\usefigure into the appropriate one (\reuseMPgraphic, ...).  

Then speaking purely hypothetically of course: If, after learning
metafun, one decides to turn many external metapost figures into
metafun figures (and then static figures instead of reusable figures),
the figure placement commands don't have change.

-Sanjoy

`Never underestimate the evil of which men of power are capable.'
         --Bertrand Russell, _War Crimes in Vietnam_, chapter 1.