# File gtk/sample/gtk-demo/cairo-line-cap.rb, line 19
    def draw(cr)
      cr.set_line_width(0.12)
      
      cr.set_line_cap(Cairo::LINE_CAP_BUTT) # default
      cr.move_to(0.25, 0.2)
      cr.line_to(0.25, 0.8)
      cr.stroke
      
      cr.set_line_cap(Cairo::LINE_CAP_ROUND)
      cr.move_to(0.5, 0.2)
      cr.line_to(0.5, 0.8)
      cr.stroke
      
      cr.set_line_cap(Cairo::LINE_CAP_SQUARE)
      cr.move_to(0.75, 0.2)
      cr.line_to(0.75, 0.8)
      cr.stroke
      
      # draw helping lines
      cr.set_source_rgba(1, 0.2, 0.2)
      cr.set_line_width(0.01)
      
      cr.move_to(0.25, 0.2)
      cr.line_to(0.25, 0.8)
      
      cr.move_to(0.5, 0.2)
      cr.line_to(0.5, 0.8)
      
      cr.move_to(0.75, 0.2)
      cr.line_to(0.75, 0.8)
      
      cr.stroke
    end