[NTG-context] How to run Typesetting in MetaPost example (MetaFun)?

Verhaag, G.C.H.M. verhaaggchm at ziggo.nl
Thu Jan 20 10:59:59 CET 2011


Aditya Mahajan wrote:

> On Tue, 18 Jan 2011, Verhaag, G.C.H.M. wrote:
>
>> Hi,
>>
>> I wanted to try (using ConTeXt minimals MkIV) the example on page 228 
>> of the MetaFun manual, dealing with typesetting in MetaPost.
>
>
> I haven't look at the metapost manual ... but
>
>> The code is given as:
>>
>> \resetMPdrawing
>> \startMPdrawing
>> picture pic[] ;
>> numeric wid[], len[], pos[], n ;
>> wid[0] := len[0] := pos[0] := n := 0 ;
>> \stopMPdrawing
>>
>> \def\whatever#1%
>> {\appendtoks#1\to\MPtoks
>> \setbox\MPbox=\hbox{\bfd\the\MPtoks}%
>> \startMPdrawing
>>  n := n + 1 ; len[n] := \the\wd\MPbox ;
>> \stopMPdrawing
>> \startMPdrawing[-]
>>  pic[n] := textext("\bfd\setstrut\strut#1") ;
>>  pic[n] := pic[n] shifted - llcorner pic[n] ;
>> \stopMPdrawing}
>>
>> \handletokens MetaPost is Fun!\with\whatever
>>
>> But is won't run. The following message is generated:
>
>
> The actual error message said
>
> ! Undefined control sequence.
> \@@toks ->\MPtoks
>
> So add
>
> \newtoks\MPtoks
>
> After which you get
>
> ! Undefined control sequence.
> \whatever ...endtoks #1\to \MPtoks \setbox \MPbox
>
> so add
>
> \newbox\MPbox
>
> After that the file compiles but you get an empty image. There are two 
> things missing in the code. First you don't tell actually draw the 
> metapost drawing. for that, add
>
> \MPdrawingdonetrue \getMPdrawing \resetMPdrawing
>
>
> Still an empty page. Again the pic[n] is calculated but never drawn. 
> So add
>
>   draw p[n] shifted (n*1cm,0) ;
>
> (or perhaps along a more sophisticated path),
>
> and now you have a working example:
>
> \newtoks\MPtoks
> \newbox\MPbox
>
> \resetMPdrawing
> \startMPdrawing
>   picture p[] ;
>   numeric wid[], len[], pos[], n ;
>   wid[0] := len[0] := pos[0] := n := 0 ;
> \stopMPdrawing
>
> \def\whatever#1%
> {\appendtoks#1\to\MPtoks
>  \setbox\MPbox=\hbox{\bfd\the\MPtoks}%
>  \startMPdrawing
>   n := n + 1 ; len[n] := \the\wd\MPbox ;
>   p[n] := textext("\bfd\setstrut\strut#1") ;
>   p[n] := p[n] shifted - llcorner p[n] ;
>   draw p[n] shifted (n*1cm,0) ;
>  \stopMPdrawing}
>
> \starttext
> \handletokens MetaPost is Fun!\with\whatever
>
> \MPdrawingdonetrue \getMPdrawing \resetMPdrawing
>
> \stoptext
>
> You could also have just used the macros from meta-txt:
>
> \useMPlibrary[txt]
>
> \startMPdefinitions
>   newpath RotPath ;
>   RotPath = fullcircle scaled 3cm ;
> \stopMPdefinitions
>
> \starttext
> \followtokens{Metapost is fun \quad}
> \stoptext
>
> @Hans: Perhaps we can have a more ConTeXtist interface to this macro:
>
> \definetextonepath
>    [whatever]
>    [color=...,
>     style=...,
>     mp=..., % path specification
>    ]
>
> \whatever{Metapost is fun}
>
> Aditya

Hi,

Okay, that makes things more clear, but couldn't find this in the 
manual! Maybe it is very obvious to someone more familiar with METAPOST.

Well, I also tried the nice macro example on page 232 of the MetaFun 
manual by Hans, and got of course the same problems. But after I added the

\newtoks\MPtoks
\newbox\MPbox

definitions to the file, it worked!

Also the Inkscape alternative is very useful, thanks for helping me out!

Regards,
Gerard


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