import sys, math, time
from OpenGL.GLUT import *
from OpenGL.GL import *
from OpenGL.GLU import *
import Image

useViewport = False
useScissor = False

def draw():
    glDisable(GL_SCISSOR_TEST)
    glClearColor(1,0,0,0)
    glClear(GL_COLOR_BUFFER_BIT)
    if useViewport:
        glViewport(100,100,350,350)
    else:
        glViewport(0,0,glutGet(GLUT_WINDOW_WIDTH),glutGet(GLUT_WINDOW_HEIGHT))
    if useScissor:
        glScissor(100,100,350,350)
        glEnable(GL_SCISSOR_TEST)
    else:
        glDisable(GL_SCISSOR_TEST)
    glClearColor(0,0,0,0)
    glClear(GL_COLOR_BUFFER_BIT)
    glBegin(GL_TRIANGLES)
    glVertex2f(-1.2,-1.2)
    glVertex2f(1.2,-1.2)
    glVertex2f(0,1.2)
    glEnd()
    glutSwapBuffers()

def keyboard(key, x, y):
    global useViewport, useScissor
    if key == chr(27):
        sys.exit(0)
    elif key == 'v':
        useViewport = not useViewport
    elif key == 's':
        useScissor = not useScissor

def idle():
    glutPostRedisplay()

glutInit([])
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB)
glutInitWindowSize(500, 500)
glutInitWindowPosition(0,0)
glutCreateWindow(sys.argv[0])
glutDisplayFunc(draw)
glutKeyboardFunc(keyboard)
glutIdleFunc(idle)
glutMainLoop()