Re: [NTG-context] metafun & \sometxt: should black be "black" or "textcolor"?

6 Aug 2006


      Taco Hoekwater wrote:
...
Hi Mojca,
Mojca Miklavec wrote:
...
But the other \sometxt was indeed red - withcolor seems to work, but
only conditionally. And I have some weird examples of two texts one
after another. In some cases (if something else is drawn inbetween and
a color changed twice), then the second text will be black. But it's
quite unpredictable (that one might even be bug in my code, so I don't
want to complain before I have an example).
Ok, I looked into this again, and I was definately wrong.
The actual problem appears to be that metapost does not write a
color switch for 'black' when it appears at the start of a file,
it simply assumes the start color is black. This could be
considered a bug in MetaPost or a missing feature in ConTeXt
(i have not decided yet :-)).
Quick fix: You can start your MP code with an explicit color
initialization.
\startMPcode
      special "0 setgray";
      ......
   \stopMPcode
A hack, I know. MetaPost should be able to distinguish between
   draw p
and
   draw p withcolor (0,0,0)
but currently it can't (because the structure is initialized
as (0,0,0)). It is not quite a bug either, because there may
well be MP code out there that depends on this.
In fact, probably code by Knuth, Hobby, Jacko, and Hans ;-)
in meta-pdf.tex:

\chardef\blackoutMPgraphic\plusone

\def\finishMPgraphic
  {\stopMPresources
   \egroup
   \setbox\scratchbox\vbox
     {\forgetall
      \hbox
        {\PDFcode{q \MPxscale\space 0 0 \MPyscale\space \MPxoffset\space \MPyoffset\space cm}%
         \ifcase\blackoutMPgraphic\or\PDFcode{0 g 0 G}\fi
         \lower\MPyshift\box\scratchbox % unscaled shift
         \PDFcode{Q}}}%
   \ht\scratchbox\MPheight
   \wd\scratchbox\MPwidth
   \dp\scratchbox\zeropoint\relax
   \dopackageMPgraphic\scratchbox
   \egroup
   \endinput}


\starttext

\color[red]{\startMPcode
draw fullcircle scaled 5cm ;
draw btex test etex ;
\stopMPcode red}

\startreusableMPgraphic{test}
draw fullcircle scaled 5cm ;
draw btex test etex ;
\stopreusableMPgraphic

\color[red]{red \reuseMPgraphic{test} red}

\stoptext


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