Working custom pyglet class.

3d.py

import pyglet, math
from pyglet.gl import *
key = pyglet.window.key

from pyglet import app
from pyglet.libs.win32 import _user32
from pyglet.libs.win32.constants import *
from pyglet.libs.win32.winkey import *
from pyglet.libs.win32.types import *

#window = pyglet.window.Window(width=800, height=600)

class main(pyglet.window.Window):
	def __init__ (self):
		super(main, self).__init__(800, 800, fullscreen = False)
		self.x, self.y = 0, 0
		self.alive = 1
		width, height = 800,600
		self.bg = pyglet.image.load('./grid.png')
		self.bg.scale = max(max(width, self.bg.width)/min(width, self.bg.width), max(self.bg.height, height)/min(self.bg.height, height))
		self.bg.texture.width = width
		self.bg.texture.height = height
		self.bg.width = width
		self.bg.height = height

		self.pos = 0
		self.lines = [[114,23], [361,122], [134,222], [250,432], [323,133], [145,155]]

	def on_draw(self):
		self.render()

	def on_close(self):
		self.alive = 0

	def draw_line(self, xy, dxy, color=(1, 0.2, 0.2, 1)):
		glColor4f(color[0], color[1], color[2], color[3])
		glBegin(GL_LINES)
		glVertex2f(xy[0], xy[1])
		glVertex2f(dxy[0], dxy[1])
		glEnd()

	def on_mouse_drag(self, x, y, dx, dy, button, modifiers):
		pass
	def on_mouse_press(self, x, y, button, modifiers):
		pass
	def on_mouse_release(self, x, y, button, modifiers):
		pass
	def on_mouse_motion(self, x, y, dx, dy):
		pass

	def on_key_release(self, symbol, modifiers):
		pass

	def on_key_press(self, symbol, modifiers):
		if symbol == key.ESCAPE: # [ESC]
			self.alive = 0

	def render(self):
		self.clear()
		self.bg.blit(0,0)

		prev = None
		self.pos += 1
		if self.pos >= len(self.lines): self.pos = 0

		for line in self.lines[:self.pos]:
			if prev is None:
				prev = [line, ]
				continue

			self.draw_line(prev[-1], line)
			prev.append(line)

		self.flip()

	def run(self):
		while self.alive == 1:
			self.render()

			# -----------> This is key <----------
			# This is what replaces pyglet.app.run()
			# but is required for the GUI to not freeze
			#
			#app.platform_event_loop.start()
			#self._allow_dispatch_event = True
			#self.dispatch_pending_events()
			#msg = MSG()
			#while _user32.PeekMessageW(byref(msg), 0, 0, 0, PM_REMOVE):
			#	_user32.TranslateMessage(byref(msg))
			#	_user32.DispatchMessageW(byref(msg))
			#	break
			#self._allow_dispatch_event = False
			
			print('Dispatching')
			event = self.dispatch_events()
			print('Done')

x = main()
x.run()