Re: simplifying repeated macro calls in metafun

[Hans Hagen <j.hagen@xs4all.nl>]

On 6/24/2021 5:42 AM, Aditya Mahajan wrote:
> On Wed, 23 Jun 2021, Aditya Mahajan wrote:
> 
>> On Thu, 24 Jun 2021, Jeong Dal wrote:
>>
>>> Now, I am trying to do the same thing using \startuseMPgraphic, but I don’t the correct result yet.
>>> Using \startuseMPgraphic, and \dorecurse, the code is simpler. But, it seems to me that \startanimation … \stopanimation is not working with \dorecurse{}{} …
>>> It just list all the graphics.
>>> Any hint is welcome.
>>
>> A while back, I wrote some code to easily generate metapost animations.
>>
>> https://adityam.github.io/context-blog/post/metapost-animation/
>>
>> I haven't used it much because I am mostly on linux, and its is a PITA to get an older version of Adobe Reader to work under wine.
> 
> Here's a version using these macros. It runs with MkIV but not with LMTX. Sorry, no time to debug what's going wrong in LMTX right now.
mp variable handling in lmtx is a bit more sophisticated

when we pass colors, numerics, dimensions there is some guess work going 
on wrt the type of the variable and on the average that works ok but in 
lmtx we can also fetch variables

so here is a basic setup for you (not much animation but it shows the idea

\unprotect

% this is similar to mkiv, although we add protection against
% overload; i should  still use the new argument handling here

\permanent\protected\def\startMPanimation
   {\dodoublegroupempty\meta_start_animation}

\permanent\protected\lettonothing\stopMPanimation

\def\meta_start_animation#1%
   {\normalexpanded{\meta_start_animation_indeed{#1}}}

\permanent\protected\def\meta_start_animation_indeed#1#2#3\stopMPanimation
 
{\gdefcsname\??mpgraphic#1\endcsname{\meta_handle_use_graphic{#1}{#2}{#3}}}

% this one is like yours too but it has more wrapping inside
% wrt namespace, picking up variables etc; as you can see,
% we just operate in the normal mp related variable namespace

\permanent\tolerant\protected\def\useMPanimation#=#*#=%
   {\meta_begin_graphic_group{#1}%
    \checkmpcategoryparent
    \let\currentmpcategory\currentMPgraphicname
    \setupcurrentmpcategory[#2]%
    \dorecurse{\mpcategoryparameter{n}}{%
       \letmpcategoryparameter{i}\recurselevel
       \begincsname\??mpgraphic#1\endcsname\empty
    }%
    \meta_end_graphic_group}

% so, the main thing here is that we added the loop and
% for convenience i store the current step

\protect

\starttext

\setupMPvariables
   [animation]
   [n=4]

% watch how we *pick up* a variable, no expansion mess, we
% avoid heuristics, it might even be faster (not that it
% matters because tex is already pretty fast)

\startMPanimation{circle}
     fill fullcircle scaled (10cm / mpvarn("i"));
\stopMPanimation

% there currently are mpvarn, mpvard, mpvars, mpvarb

\useMPanimation{circle}{n=4}

\stoptext



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