Hi Fabrice,

In order to have the box aligned with the text, it is enough to use the  \lower command as in the exmaple below.
Best regards: Otared K.

%% begin
\startuniqueMPgraphic{MyShape}
	path p ; 
	p := unitsquare xscaled \overlaywidth yscaled \overlayheight ;
	pickup pencircle scaled \overlaylinewidth ;
	fill p withcolor \MPcolor{\overlaycolor} ;
	draw p withcolor \MPcolor{\overlaylinecolor} ;
\stopuniqueMPgraphic
\setuplayout[grid=yes]
\defineoverlay[MyBackgroundLayer][\uniqueMPgraphic{MyShape}]

\define[1]\MyExoCommand{%
	\lower\strutdepth\hbox{\startframed
		[background=MyBackgroundLayer,
		frame=off,
%		width=3cm,
		align=flushleft,
		backgroundcolor=darkred]
		{\white Exercice #1}
	\stopframed}
	}
\defineenumeration[ex]
	[text=,
	title=yes,
	titleleft=,
	titleright=,
	width=fit,
	alternative=top,
	number=yes,
	numbercommand=\MyExoCommand]


\showgrid
\starttext

\startex{Pour tous les candidats \hfill 5 points}
  \input ward
\stopex

\stoptext
%% end

> On 29 Jan 2017, at 23:04, Fabrice Couvreur <fabrice1.couvreur@gmail.com> wrote:
> 
> Hello Kavian,
> Thank you for your answer, it's good for the parentheses. For the command, I found only this which does not exactly answer what I want to do.
> Fabrice
> 
> \defineenumeration
>   [ex]
>   [text={Exercice},
>    headcommand=\EXFRAME,
>    titleleft=,
>    titleright=,
>    title=yes,
>    width=fit,
>    numberconversionset=ACCONVERSION,
>    alternative=top,
>    number=yes]
> 
> 2017-01-29 12:02 GMT+01:00 Otared Kavian <otared@gmail.com <mailto:otared@gmail.com>>:
> Hi Fabrice,
> 
> To suppress the parentheses in the title, you can use the keys titleleft and titleright as in the following:
> 
> \defineenumeration
>   [ex]
>   [text=Exercice,
>    title=yes,
>    titleleft=,
>    titleright=,
>    width=fit,
>    numberconversionset=ACCONVERSION,
>    alternative=top,
>    number=yes]
> 
> In order to put the word « Exercice » in the frame you should define a special command, for instance \MyTextCommand and the say text = \MyTextCommand
> 
> Best regrads: OK
> 
>> On 29 Jan 2017, at 09:07, Fabrice Couvreur <fabrice1.couvreur@gmail.com <mailto:fabrice1.couvreur@gmail.com>> wrote:
>> 
>> Hello,
>> I would like a title without the parentheses and the text "Exercice" in the frame with the number.
>> Thank you.
>> Fabrice
>> 
>> \defineframed
>>   [EXFRAME]
>>   [frame=off,
>>    offset=0pt,
>>    location=low,
>>    width=\struttotal,
>>    background=color,
>>    backgroundcolor=darkred,
>>    foregroundcolor=white,
>>    forgroundstyle=bold]
>> 
>> \defineprocessor[ACPROCESSOR][command=\EXFRAME]
>> \defineconversionset[ACCONVERSION][][ACPROCESSOR->n]
>> 
>> \defineenumeration
>>   [ex]
>>   [text=Exercice,
>>    title=yes,
>>    width=fit,
>>    numberconversionset=ACCONVERSION,
>>    alternative=top,
>>    number=yes]
>> 
>> \starttext
>> 
>> \startex{Pour tous les candidats \hfill 5 points}
>>   \input ward
>> \stopex
>> 
>> \stoptext
> 
> 
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