#!/usr/bin/env python

"""
This program draws a single red rectangle in a blue background.
It is a demonstration of the structure needed to mix
Python + PyQt (for the window control) + PyOpenGL.
Code includes commented-out lines to use the more efficient
OpenGL Displays lists.
"""

#import pydoc #Not used

__author__= "Joseph O'Rourke"
__version__ = "1.0"
__date__= "31Aug06"

import sys
#import math #Not used
from qt import *
from qtgl import *
from OpenGL.GL import *

##############################################################################
def rect():
    """
    Draw a single rectangle in the first quadrant.
    Assumes [0,1]^3 coordinate system.
    """
    glColor3f (1.0, 0.0, 0.0) #Red
    glBegin(GL_POLYGON)
    glVertex3f (0.25, 0.25, 0.0)
    glVertex3f (0.75, 0.25, 0.0)
    glVertex3f (0.75, 0.75, 0.0)
    glVertex3f (0.25, 0.75, 0.0)
    glEnd()


##############################################################################
class MyWidget(QGLWidget):
    """
    All the stuff necessary to make Qt + QtOpenGL work together
    """
        
    def __init__(self,parent=None,name=None):
        QGLWidget.__init__(self,parent,name)
        self.startTimer(100) # milliseconds

    def timerEvent(self,event):
        self.updateGL()

    def paintGL(self):
        """
        What to do when the screen is repainted: draw the rectangle.
        """
        glClear( GL_COLOR_BUFFER_BIT )
        rect()
        #How to do it instead via a CallList:
        #glCallList(self.rect1)
        
    def resizeGL(self,width,height):
        """
        What to do when the window is resized: reset coord system etc.
        """
        w = width / float(height)
        h = 1.0

        glViewport( 0, 0, width, height )
        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
        glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0) # Use orthog proj, [0,1]^3
        # Note: first four numbers are xmin, xmax, ymin, ymax.
        glMatrixMode(GL_MODELVIEW)
        glLoadIdentity()

    def initializeGL(self):
        """
        Upon first invocation
        """
        glClearColor(0.0, 0.0, 1.0, 0.0)

        #This is how to set up a display list, whose invocation by glCallList
        #would display the rectangle:
        #self.rect1=glGenLists(1)
        #glNewList(self.rect1,GL_COMPILE)
        #rect()
        #glEndList()


##############################################################################
if __name__=='__main__':
      QApplication.setColorSpec(QApplication.CustomColor)
      app=QApplication(sys.argv)

      if not QGLFormat.hasOpenGL():
            raise 'No Qt OpenGL support.'

      widget=MyWidget()
      app.setMainWidget(widget)
      widget.show()
      app.exec_loop()