cairo and gtk on ruby

cairo and gtk

# -*- coding: utf-8 -*-
require 'cairo'
require 'gtk2'

format = Cairo::FORMAT_ARGB32
width = 300
height = 200
radius = height / 3
window = Gtk::Window.new('Graph')
window.set_default_size(width, height)
window.signal_connect('destroy') do
  Gtk.main_quit
end

area = Gtk::DrawingArea.new
area.signal_connect('expose_event') do
  context = area.window.create_cairo_context
  # background
  context.set_source_rgb(1, 1, 1) # white
  context.rectangle(0, 0, width, height)
  context.fill

  context.set_source_rgb(1, 0, 0) # red
  context.arc(width / 2, height / 2, radius, 0, 2 * Math::PI)
  context.fill
  # text string
  context.set_source_rgb(0, 0, 0)
  context.set_font_size( 12 )
context.move_to(0,100)
str = "文字コードの自動判別 -- Text String"
context.show_text( str )

end

window.add(area)
window.show_all

Gtk.main