end
  elseif chord == 'C-m' then
    local drawing,i,shape = select_shape_at_mouse()
    if drawing then
      convert_horvert(drawing,i,shape)

end
-- turn a stroke into either a horizontal or vertical line
function convert_horvert(drawing, i, shape)
  local x1,y1 = shape[1].x, shape[1].y
  local x2,y2 = shape[#shape].x, shape[#shape].y
  if math.abs(x1-x2) > math.abs(y1-y2) then
    drawing.shapes[i] = {{x=x1, y=y1}, {x=x2, y=y1}}
  else
    drawing.shapes[i] = {{x=x1, y=y1}, {x=x1, y=y2}}
  end