vardef mycircle =
  save c ; picture c ; c := nullpicture ;
  addto c contour fullcircle scaled 2mm ;
  c
enddef ;

def test (expr m) expr p =
  path _p_ ; _p_ := p ;
  scantokens m
enddef ;

def only_clip text t =
  begingroup
    save c ; picture c ; c := mycircle ;
    clip c to bbox (c scaled 0.5) ;
    addto currentpicture also c t ;
    addto currentpicture doublepath _p_ t ;
  endgroup
enddef ;


def no_clip text t =
  begingroup
    save c; picture c ; c := mycircle ;
    addto currentpicture also c t ;
    addto currentpicture doublepath _p_ t ;
  endgroup
enddef ;


def draw_clip text t =
  begingroup
    save c ; picture c ; c := mycircle ;
    draw bbox (c scaled 0.5) ;
    clip c to bbox (c scaled 0.5) ;
    addto currentpicture also c t ;
    addto currentpicture doublepath _p_ t ;
  endgroup
enddef ;

beginfig(1)
  
  for macro = "only_clip", "no_clip", "draw_clip":
    test( macro ) (0,0) -- (1cm,0) dashed evenly ;
    % NOTE:
    % Drawing the label here makes the weird second dashed line go away.
    % label.rt(macro, (-5cm,0) );
    currentpicture := currentpicture shifted (-2cm,0) ;
    test( macro ) (0,0) -- (1cm,0) ;
    label.rt(macro, (-5cm,0) );
    currentpicture := currentpicture shifted(2cm,0.5cm );
  endfor

endfig ;
end