Traceback (most recent call last):
File "_ctypes/callbacks.c", line 234, in 'calling callback function'
File "C:\Users\Greg\AppData\Local\Programs\Python\Python36\lib\site-packages\pyglet\window\win32\__init__.py", line 656, in f
result = event_handler(msg, wParam, lParam)
File "C:\Users\Greg\AppData\Local\Programs\Python\Python36\lib\site-packages\pyglet\window\win32\__init__.py", line 992, in _event_size
self.switch_to()
File "C:\Users\Greg\AppData\Local\Programs\Python\Python36\lib\site-packages\pyglet\window\win32\__init__.py", line 328, in switch_to
self.context.set_current()
File "C:\Users\Greg\AppData\Local\Programs\Python\Python36\lib\site-packages\pyglet\gl\win32.py", line 243, in set_current
super(Win32Context, self).set_current()
File "C:\Users\Greg\AppData\Local\Programs\Python\Python36\lib\site-packages\pyglet\gl\base.py", line 327, in set_current
raise RuntimeError('Canvas has not been attached')
RuntimeError: Canvas has not been attached