#!/usr/bin/ruby
require "opengl"
require "glut"

STDOUT.sync=TRUE
disp = Proc.new {
  GL.Clear(GL::COLOR_BUFFER_BIT)
  GL.Begin(GL::TRIANGLES)
    GL.Color(0.0, 0.0, 1.0)
    GL.Vertex(0, 0)
    GL.Color(0.0, 1.0, 0.0)
    GL.Vertex(200, 200)
    GL.Color(1.0, 0.0, 0.0)
    GL.Vertex(20, 200)
  GL.End
  GL.Flush
}

reshape = Proc.new {|w, h|
  GL.Viewport(0, 0, w, h)
  GL.MatrixMode(GL::PROJECTION)
  GL.LoadIdentity
  GL.Ortho(0, w, 0, h, -1, 1)
  GL.Scale(1, -1, 1)
  GL.Translate(0, -h, 0)
}

GLUT.Init
a =  GLUT.CreateWindow("single triangle");
GLUT.DisplayFunc(disp);
GLUT.ReshapeFunc(reshape);
GLUT.MainLoop;