#!/usr/bin/env python

from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *
import math

window = 0                                             # glut window number
width, height = 500, 400                               # window size

def refresh2d(width, height):
  glViewport(0, 0, width, height)
  glMatrixMode(GL_PROJECTION)
  glLoadIdentity()
  glOrtho(0.0, width, 0.0, height, 0.0, 1.0)
  glMatrixMode (GL_MODELVIEW)
  glLoadIdentity()

def draw_circle(cx, cy, r, segments):
  theta = 2.0 * math.pi / segments
  tangetial_factor = math.tan(theta)
  radial_factor = math.cos(theta)
  x = float(r)
  y = 0.0
  glBegin(GL_LINE_LOOP)
  for index in range(segments):
    glVertex2f(x + cx, y + cy)
    tx = -y
    ty = x
    x += (tx * tangetial_factor)
    y += (ty * tangetial_factor)
    x *= radial_factor
    y *= radial_factor
  glEnd()

def draw_arc(cx, cy, r, start_angle, arc_angle, segments):
  theta = (arc_angle / float(segments)) -1
  tangetial_factor = math.tan(math.radians(theta))
  radial_factor = math.cos(math.radians(theta))
  x = r * math.cos(math.radians(float(start_angle)))
  y = r * math.sin(math.radians(float(start_angle)))
  glBegin(GL_LINE_STRIP)
  for index in range(segments):
    glVertex2f(x + cx, y + cy)
    tx = -y
    ty = x
    x += (tx * tangetial_factor)
    y += (ty * tangetial_factor)
    x *= radial_factor
    y *= radial_factor
  glEnd()

def draw_circle_slow(cx, cy, r, segments):
  glBegin(GL_LINE_LOOP)
  for index in range(segments):
    theta = 2.0 * math.pi * float(index) / float(segments)
    x = r * math.cos(theta)
    y = r * math.sin(theta)
    glVertex2f(x + cx, y + cy)
  glEnd()

def draw_rect(x, y, width, height):
  glBegin(GL_QUADS)                                  # start drawing a rectangle
  glVertex2f(x, y)                                   # bottom left point
  glVertex2f(x + width, y)                           # bottom right point
  glVertex2f(x + width, y + height)                  # top right point
  glVertex2f(x, y + height)                          # top left point
  glEnd()                                            # done drawing a rectangle

def draw_line(x1, y1, x2, y2):
  glBegin(GL_LINES)
  glVertex2f(x1, y1)
  glVertex2f(x2, y2)
  glEnd()

def draw():                                            # ondraw is called all the time
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) # clear the screen
  glLoadIdentity()                                   # reset position
  refresh2d(width, height)                           # set mode to 2d
  #glColor3f(0.0, 0.0, 1.0)                           # set color to blue
  #draw_rect(10, 10, 200, 100)                        # rect at (10, 10) with width 200, height 100
  glColor3f(1.0, 1.0, 1.0) # set color to white
  #draw_line(10, 250, 200, 250)
  #draw_line(200, 250, 200, 10)
  draw_circle(250.0, 200.0, 50.0, 64)
  # draw arc x center, y center, radius, start angle, included angle, number of segments
  draw_arc(250.0, 200.0, 150.0, 0.0, 180.0, 30)
  #glNormal3d(0.0, 0.0, 1.0)
  #draw_circle_slow(250.0, 250.0, 50.0, 8)
  glutSwapBuffers()                                  # important for double buffering

# initialization
glutInit()                                             # initialize glut
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH)
glutInitWindowSize(width, height)                      # set window size
glutInitWindowPosition(0, 0)                           # set window position
window = glutCreateWindow("Nuts.com")                  # create window with title
glutDisplayFunc(draw)                                  # set draw function callback
#glutIdleFunc(draw)                                     # draw all the time
glutMainLoop()                                         # start everything