vardef bouton(expr txt) =
    picture $;
    path $$;
    pair BLLC,BULC,BURC,BLRC;
    numeric RRAY,wray;
    wray = 4pt;
    RRAY = 1-1/sqrt(2);
    $ = thelabel(txt,(0,0)); % acquisition du texte à encadrer sous forme d'image
    BLLC = (0,0)  ; BULC = (0,14);
    BURC = (50,14); BLRC = (50,0);
    % construction du bord de la boîte
    $$ = (BLLC + (0,wray)) -- (BULC - (0,wray)) .. (BULC + RRAY*(wray,-wray)) .. 
	 (BULC + (wray,0)) -- (BURC - (wray,0)) .. (BURC - RRAY*(wray,wray)) .. 
	 (BURC - (0,wray)) -- (BLRC + (0,wray)) .. (BLRC + RRAY*(-wray,wray)) .. 
	 (BLRC - (wray,0)) -- (BLLC + (wray,0)) .. (BLLC + RRAY*(wray,wray)) .. cycle;
    fill $$ withcolor (1,1,0.7);
    draw $ shifted (25,7);
    draw $$ withcolor (0,0,.3) withpen pencircle scaled 1;
enddef;