I tried the following code of yours, but I got “! undefined control sequence” error.
\setupbodyfont[pagella,11pt]
\setupcolors[state=start]
\defineframedtext
[MyFrame]
[before={\blank},
after={\blank},
frame=off,
background=MyFrame,
%width=\textwidth,
width=max,
height=fit,
style=italic]
\definelabel
[Définition]
[headstyle=\bf\smallcaps]
\startuseMPgraphic{MyFrame}
path b;
picture p;
%p := textext.rt("\white\Définition");
p := textext.rt("\white\framedtextparamemter{Title}");
%p := textext.rt("\white\getvariable{text}{text1}");
p := p shifted (2BodyFontSize,OverlayHeight-ypart center p+.25ExHeight);
b := boundingbox p leftenlarged .5EmWidth rightenlarged .5EmWidth;
fill OverlayBox withcolor lightgray; %\MPcolor{
fill b withcolor darkred;
draw bottomboundary OverlayBox withpen pencircle scaled 1pt withcolor
darkred;
draw topboundary OverlayBox withpen pencircle scaled 1pt withcolor
darkred;
draw p;
setbounds currentpicture to boundingbox currentpicture enlarged 2mm;
\stopuseMPgraphic
\defineoverlay
[MyFrame]
[\useMPgraphic{MyFrame}]
\starttext
\showframe
\startMyFrame[Title=Hans]
\input knuth
\stopMyFrame
\startMyFrame[Title=Hagen]
\input knuth
\stopMyFrame
\stoptext
…..
tex error > tex error on line 52 in file /Users/graph/Documents/TeXfiles/test.tex: ! Undefined control sequence
<argument> ... p := textext.rt("\white \framedtextparamemter
{Title}"); p := p shifted ...
\meta_process_graphic ...currentMPformat }data {#1
;}initializations {\meta_f...
\meta_handle_use_graphic ...a_process_graphic {#3}
\endgroup
\meta_use_graphic ...me \??mpgraphic #1\endcsname
\empty \meta_end_graphic_g...
<to be read again>
\else
\executedefinedoverlay ...e \everyoverlay #2\else
\lower \d_framed_target_dp...
...
l.52 \stopMyFrame
42
43 \defineoverlay
44 [MyFrame]
45 [\useMPgraphic{MyFrame}]
46
47 \starttext
48
49 \showframe
50 \startMyFrame[Title=Hans]
51 \input knuth
52 >> \stopMyFrame
53
54 \startMyFrame[Title=Hagen]
55 \input knuth
56 \stopMyFrame
57
58 \stoptext