Hi Fabrice,

Your code works if you add 

	 setbounds currentpicture to OverlayBox ;

Indeed with this Metapost determines the boundaries of the rectangle of which you draw the left side.

Best regards: OK

> On 30 Aug 2015, at 09:50, Fabrice Couvreur <fabrice1.couvreur@gmail.com> wrote:
> 
> Hi,
> Hans Otared and thank you for your suggestions.
> A question for Hans : why my code does not give the expected result ?
> Fabrice
> 
> 2015-08-29 13:35 GMT+02:00 Hans Hagen <pragma@wxs.nl <mailto:pragma@wxs.nl>>:
> On 8/29/2015 1:11 PM, Otared Kavian wrote:
> Hi fabrice,
> 
> I dont’t know whether this the best solution, but you can use the following definition of the MPgraphic Funny:
> 
> \startuseMPgraphic{Funny}
>      interim linecap := butt ;
>      path p ;
>      p := unitsquare xyscaled (OverlayWidth,OverlayHeight) ;
>      drawoptions (withpen pencircle scaled 6.5pt withcolor \MPcolor{MyColorA}) ;
>      draw lrcorner p --urcorner p --ulcorner p withcolor white;
>      draw ulcorner p --llcorner p ;
> 
> \stopuseMPgraphic
> 
> \startuseMPgraphic{Funny}
>     interim linecap := butt ;
>     draw leftboundary OverlayBox ;
>     setbounds currentpicture to OverlayBox ;
> \stopuseMPgraphic
> 
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