libharu：HPDFPage#set_line_join

everyday Ruby 
#!/usr/bin/env ruby

require "hpdf"

pdf  = HPDFDoc.new
page = pdf.add_page

page.set_line_width(30)

y = 100
[HPDFDoc::HPDF_MITER_JOIN,
 HPDFDoc::HPDF_ROUND_JOIN,
 HPDFDoc::HPDF_BEVEL_JOIN].each do |x|
  page.set_line_join(x)

  page.move_to(100, y)
  page.line_to(150, y+20)
  page.line_to(200, y)
  page.stroke
  y += 100
end

pdf.save_to_file(File.basename($0, ".rb") + ".pdf")

HPDFDoc::HPDF_BEVEL_JOIN の違いが良く分からない…