pyglet: on_resize breaks graphics

I’m writing an application with pyglet where all rendered objects are children of the window class. I’m trying to draw a simple rectangle, but using on_resize seems to break everything. There’s no error message, it just doesn’t draw the rectangle.

This is my file structure:

main.py
lib
 |-- window.py
 |-- quad.py

This code doesn’t work, but if I remove the on_resize methods it does:

-------------
FILE: main.py
-------------

import pyglet
import lib

window = lib.window.Window(1280, 720)

window.add_object(lib.quad.Quad())

pyglet.app.run()


-------------------
FILE: lib/window.py
-------------------

import pyglet

from . import quad

class Window(pyglet.window.Window):
    def __init__(self, w, h):
        super().__init__(width=w, height=h)
        self.objects = []

    def on_draw(self):
        for obj in self.objects:
            obj.on_draw()

    def on_resize(self, width, height):
        for obj in self.objects:
            obj.on_resize(width, height)

    def add_object(self, obj):
        self.objects.extend([obj])


-------------
FILE: lib/quad.py
-------------

import pyglet
import pyglet.gl

class Quad():
    def __init__(self):
        self.quad = pyglet.graphics.vertex_list(4, ('v2i', (10, 10,  100, 10, 100, 100, 10, 100)), ('c3B', (0, 0, 255, 0, 0, 255, 0, 255, 0,  0, 255, 0)))

    def on_draw(self):
        self.quad.draw(pyglet.gl.GL_QUADS)

    def on_resize(self, width, height):
        pass

I would like to be able to keep rendered objects as children of the window class, since that makes running event handlers much easier. Is there any way that I can make this work with the on_resize handler? Any help is appreciated.

EDIT: I tried removing on_resize from the Quad class, and making on_resize do nothing in the Window class. It seems like the existence of the on_resize function is the issue–if on_resize exists, pyglet wont draw the rectangle.

Answer

In the on_resize method add the glViewport function call. And also don’t forget to set up an orthogonal projection. Take a look at my code, it draws a triangle at the center of the screen.

from pyglet.gl import *

class Triangle:
    def __init__(self):
        self.vertices = pyglet.graphics.vertex_list(3, ('v3f', [0,0,0, 300,0,0, 150,300,0]),
                                                       ('c3B', [255,0,0, 0,255,0, 0,0,255]))

    def draw(self):
        self.vertices.draw(GL_TRIANGLES)


class MyWindow(pyglet.window.Window):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.set_minimum_size(400, 300)
        glClearColor(0.2, 0.25, 0.2, 1.0)

        glOrtho(0, 1280, 0, 720, -10, 10) # setup orthogonal projection

        self.triangle = Triangle()

    def on_draw(self):
        self.clear()
        glPushMatrix()
        glTranslatef(640-150 ,360-150, 0) # translate the Triangle to the center
        self.triangle.draw()
        glPopMatrix()

    def on_resize(self, width, height):
        glViewport(0, 0, width, height) # resize the viewport


if __name__ == "__main__":
    MyWindow(1280, 720, 'My window', resizable=True)
    pyglet.app.run()