coordinates changed when migrating from pygame+rabbyt to pyglet+rabbyt

I'm working on a 2D game and decided to switch from SDL to OpenGL. I took rabbyt as an opengl wrapper for rendering my sprites and using pymunk (chipmunk) for my physics. I used pygame for creating the window and rabbyt for drawing the sprites on the screen.

I discovered that with pygame+rabbyt the (0,0) coordinate is in the middle of the screen. I liked that fact, because the coordinate representation in the physics engine were the same as in my graphics engine (I don't have to recalculate the coordinates when rendering the sprites).

Then I switched to pyglet because I wanted to draw lines with OpenGL - and discovered that suddenly the (0,0) coordinate was at the bottom left of the screen.

I suspected that that has something to do with the glViewport function, but only rabbyt executes that function, pyglet touches it only when the window is resized.

How can I set the (0,0) coordinate at the middle of the Screen?

I'm not very familiar with OpenGL and couldn't find anything after several hours googling and trial&error... I hope someone can help me :)

Edit: Some additional information :)

This is my pyglet screen initialization code:

self.window = Window(width=800, height=600)
rabbyt.set_viewport((800,600))
rabbyt.set_default_attribs()

This is my pygame screen initialization code:

display = pygame.display.set_mode((800,600), \
  pygame.OPENGL | pygame.DOUBLEBUF)
rabbyt.set_viewport((800, 600))
rabbyt.set_default_attribs()

Edit 2: I looked at the sources of pyglet and pygame and didn't discover anything in the screen initialization code that has something to do with the OpenGL viewport... Here is the source of the two rabbyt functions:

def set_viewport(viewport, projection=None):
    """
    ``set_viewport(viewport, [projection])``

    Sets how coordinates map to the screen.

    ``viewport`` gives the screen coordinates that will be drawn to.  It
    should be in either the form ``(width, height)`` or
    ``(left, top, right, bottom)``

    ``projection`` gives the sprite coordinates that will be mapped to the
    screen coordinates given by ``viewport``.  It too should be in one of the
    two forms accepted by ``viewport``.  If ``projection`` is not given, it
    will default to the width and height of ``viewport``.  If only the width
    and height are given, ``(0, 0)`` will be the center point.
    """
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    if len(viewport) == 4:
        l, t, r, b = viewport
    else:
        l, t = 0, 0
        r, b = viewport
    for i in (l,t,r,b):
        if i < 0:
            raise ValueError("Viewport values cannot be negative")
    glViewport(l, t, r-l, b-t)

    if projection is not None:
        if len(projection) == 4:
            l, t, r, b = projection
        else:
            w,h = projection
            l, r, t, b = -w/2, w/2, -h/2, h/开发者_开发技巧2
    else:
        w,h = r-l, b-t
        l, r, b, t = -w/2, w/2, -h/2, h/2
    glOrtho(l, r, b, t, -1, 1)
glMatrixMode(GL_MODELVIEW)
glLoadIdentity()

def set_default_attribs():
    """
    ``set_default_attribs()``

    Sets a few of the OpenGL attributes that sprites expect.

    Unless you know what you are doing, you should call this at least once
    before rendering any sprites.  (It is called automatically in
    ``rabbyt.init_display()``)
    """
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE)
    glEnable(GL_BLEND)
    #glEnable(GL_POLYGON_SMOOTH)

Thanks, Steffen

As l33tnerd suggested the origin can be placed at the center with glTranslatef... I added the following below my screen initialization code:

pyglet.gl.glTranslatef(width/2, height/2, 0)

Thanks!