ConTeXt : frame problems

Question

I'm trying to define fancy frames with ConTeXt, but I get some difficulties. Since I found many examples of this, I mainly used Metapost, but since I'm more of a TiKz adept, I don't really understand what is going on.

First I tried to use a framedtext environment, but it misbehaves when embedding a figure (which is something I often need). This is the frame as I'd like it.

\usesymbols[mvs]
\definesymbol[info][{\symbol[martinvogel 2][Info]}]

\startuseMPgraphic{mp:axiomframe}
  draw (OverlayWidth,OverlayHeight) -- (0,OverlayHeight) -- (0,0);
  draw (0.5pt,0) -- (OverlayWidth,0) -- (OverlayWidth,OverlayHeight-
    0.5pt) withpen pencircle scaled 1.2bp;
  fill OverlayBox withcolor 0.95 white;
  fill bbox textext.top("\tfd\symbol[info]") shifted 
   (0.5EmWidth,OverlayHeight-3ExHeight) withcolor white;
  draw textext.top("\tfd\symbol[info]") shifted 
   (0.5EmWidth,OverlayHeight-3ExHeight) ;
  setbounds currentpicture to OverlayBox ;
\stopuseMPgraphic
\defineoverlay[axiomframe][\useMPgraphic{mp:axiomframe}]
\defineframedtext[theoremFrame]
             [frame=off,
               rulethickness=1pt,
               offset=5pt,
               background=axiomframe,
               width=fit,
               location=middle]

\def\starttheorem{\dosingleempty\doStarttheorem}
\def\doStarttheorem[#1]{
  \starttheoremFrame
    \iffirstargument \hskip2em {\bfa #1} \\ \fi
}
\def\stoptheorem{\stoptheoremFrame}

\useexternalfigure[ctanlion]
  [http://www.ctan.org/lion/ctan_lion_350x350.png][width=5cm]

\starttext
\starttheorem[Hello]
  \placefigure[here,right,none]{}{\externalfigure[ctanlion]}
  \input knuth
\stoptheorem

Then I tried with a textbackground ; I changed the overlay and framedtext definitions with

\definetextbackground[theoremFrame]
                 [mp=mp:axiomframe,
             leftoffset=2\bodyfontsize,rightoffset=.5\bodyfontsize,
             topoffset=.5\bodyfontsize,bottomoffset=.5\bodyfontsize,
             before={\testpage[3]\blank},
             after={\blank[2*medium]},
             width=local]

This resolves the float problem, but leads to the following problem : the frame takes all the page instead of the required space, and I couldn't manage to get spaces on the edges :

Finally, I tried to modify the MP part using a document from Aditya :

\startuseMPgraphic{mp:axiomframe}
  path p;
  for i = 1 upto nofmultipars :
    p = (multipars[i] topenlarged 0pt bottomenlarged 0pt);
    fill p withcolor 0.95white ;
    draw p withcolor black withpen pencircle scaled 
     \MPvar{linewidth};
  endfor;
  fill bbox textext.top("\tfd\symbol[info]") shifted 
    (0.5EmWidth,OverlayHeight-3ExHeight) withcolor white;
  draw textext.top("\tfd\symbol[info]") shifted 
    (0.5EmWidth,OverlayHeight-3ExHeight) ;
  setbounds currentpicture to OverlayBox ;
\stopuseMPgraphic

But it doesn't behave well, and it doesn't seem to permit variable line thickness (and I couldn't find any documentation on the multipars array...)

Answer 1

I recommend using textbackground, because this can break across pages. Therefore I adapted Wolfgang's solution from Frame whole sections in ConTeXt.

\usesymbols[mvs]
\definesymbol[info][{\symbol[martinvogel 2][Info]}]

\startuseMPgraphic{mp:axiomframe}
  begingroup;
    for i=1 upto nofmultipars :
      % Draw the surrounding box
      path p;
      p := ( llcorner multipars[i]
             -- lrcorner multipars[i]
             -- urcorner multipars[i]
             -- ulcorner multipars[i]
             -- cycle )
             enlarged (EmWidth,EmWidth) ;
      fill p withcolor boxfillcolor ;
      draw p withcolor boxlinecolor ;
      draw (p cutbefore point 2 of p cutafter point 4 of p)
            withpen pencircle scaled 2pt
            withcolor boxlinecolor ;
      % Draw the info symbol
      picture pic;
      pic := textext.ulft("\tfd\symbol[info]");
      pic := pic shifted ulcorner multipars[i];
      fill bbox pic withcolor white;
      draw pic;
    endfor ;
  setbounds currentpicture to OverlayBox ;
  endgroup;
\stopuseMPgraphic

\definetextbackground
  [theoremFrame]
  [mp=mp:axiomframe,
   location=paragraph,
   backgroundcolor=green,
   framecolor=red,
   before={\testpage[3]\blank},
   after={\blank[2*medium]}]

\defineenumeration
  [theorem]
  [text=,
   number=no,
   title=yes,
   titledistance=2em,
   titleleft=,
   titleright=,
   before={\starttextbackground[theoremFrame]},
   after={\stoptextbackground}]

\useexternalfigure[ctanlion]
  [http://www.ctan.org/lion/ctan_lion_350x350.png][width=5cm]

\starttext
\starttheorem[title=Hello]
  \placefigure[here,right,none]{}{\externalfigure[ctanlion]}
  \input knuth
\stoptheorem

\input lorem

\starttheorem[title=Hello]
  \placefigure[here,right,none]{}{\externalfigure[ctanlion]}
  \input knuth
\stoptheorem
\stoptext