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


class frameRateClock:
    def __init__(self):
        self.frameCount = 0
        self.startTime = time.time()
        self.fps = 0
        self.framesToCount = 50
    def update(self):
        t = time.time()
        self.frameCount = self.frameCount + 1
        if self.frameCount == self.framesToCount:
            self.fps = float(self.framesToCount) / (t - self.startTime)
            self.startTime = t
            self.frameCount = 0

fpsclock = frameRateClock()
numTriangles = 1000

def draw():
    glClear(GL_COLOR_BUFFER_BIT)
    glViewport(0, 40, glutGet(GLUT_WINDOW_WIDTH), glutGet(GLUT_WINDOW_HEIGHT)-40)
    glBegin(GL_TRIANGLES)
    for i in range(0,numTriangles):
        glColor3f(random.random(), random.random(), random.random())
        glVertex2f(random.uniform(-1,1), random.uniform(-1,1))
        glVertex2f(random.uniform(-1,1), random.uniform(-1,1))
        glVertex2f(random.uniform(-1,1), random.uniform(-1,1))
    glEnd()
    glViewport(0, 0, glutGet(GLUT_WINDOW_WIDTH), 40)
    glColor3f(1,1,1)
    glRasterPos2f(-0.95, -0.95)
    drawBitmapString('%d triangles, %.2f fps' % (numTriangles, fpsclock.fps))
    glutSwapBuffers()
    fpsclock.update()

def drawBitmapString(text, font=GLUT_BITMAP_TIMES_ROMAN_24):
    for c in text:
        glutBitmapCharacter(font, ord(c))

def keyboard(key, x, y):
    global numTriangles
    if key == chr(27):
        sys.exit(0)
    elif key == '=':
        numTriangles += 1000
    elif key == '-':
        if numTriangles > 1000:
            numTriangles -= 1000

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()