from OpenGL.GL import *       # import the main gl library, e.g., glViewport
from OpenGL.GLU import *      # import the gl utility library, e.g., gluOrtho2D
from OpenGL.GLUT import *     # import GL Utility Toolkit, windowing lib, e.g., glutCreateWindow

def display():
    print 'display'
    # clear up the color array
    glClear( GL_COLOR_BUFFER_BIT )
    # give an array of 2D vertices
    glVertexPointerf( [[0.1, 0.9],
                       [0.9, 0.1]] )
    # draw lines, starting from zero, use two vertices
    glDrawArrays( GL_LINES, 0, 2 )
    # same for a different array
    glVertexPointerf( [[0.1, 0.1],
                       [0.9, 0.9]] )
    glDrawArrays( GL_LINES, 0, 2 )
    # tell opengl to draw all the commands that were passed in
    glFlush()

def myInit():
    # set up the background color to red, alpha zero
    glClearColor( 1,0,0,0 )
    # set the current drawing color to white
    glColor3( 1,1,1 )
    # enable the use of vertex arrays
    glEnableClientState( GL_VERTEX_ARRAY )
    
def reshape(w,h):
    print 'reshape'
    # set up the viewport to be the full window
    glViewport( 0,0,w,h )
    # start changing the projection matrix
    glMatrixMode( GL_PROJECTION )
    # clear it to identity matrix
    glLoadIdentity()
    # multiply the identity matrix with a matrix that uses
    # orthographic projection, sets the coordinate system
    # from 0 to 1 in both x and y
    gluOrtho2D( 0,1,0,1 )
    # usually we only modify modelview matrix in the programs,
    # so set the matrixmode to modelview so don't accidentally
    # change the projection matrix
    glMatrixMode( GL_MODELVIEW )

def mouse(button, state, x, y):
    print 'mouse', button, state, x, y

def motion(x, y):
    print 'motion', x, y

def kb(key, x, y):
    print 'kb', key, ord(key), x, y

def main():
    # initialized glut library
    glutInit( [] )
    # prepare for the window you are going to ask for
    glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB )
    glutInitWindowSize( 300,300 )
    glutInitWindowPosition( 300,100 )
    # get the window, give it a title string
    glutCreateWindow( 'Hello GLUT!' )
    # set up the callback functions for various events
    glutReshapeFunc( reshape )
    glutDisplayFunc( display )
    glutMouseFunc( mouse )
    glutMotionFunc( motion )
    glutKeyboardFunc( kb )
    # call my own init to set up basic opengl state
    myInit()
    # release control to the glut main event loop
    glutMainLoop()

# after all the functions have been declared, just call the main() function
# note that main is not a special name like in C or Java
main()