"Task exception was never retrieved" and "TypeError" while zooming

[bewantbe]

Steps to reproduce:
(use Chrome/Firefox as the default browser)
(in Win10 cmdline)

D:\code\py>python
Python 3.6.7 (v3.6.7:6ec5cf24b7, Oct 20 2018, 13:35:33) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import vpython
>>> vpython.__version__
'7.5.1'
>>> vpython.sphere()
<vpython.vpython.sphere object at 0x000001FB85AD1A90>
>>>

Now a browser is opened and the sphere is shown correctly. Zoom in the object sufficiently (probably with other operations, with touch screen), the following will then repeatedly shown:

Task exception was never retrieved
future: <Task finished coro=<WSserver.onMessage() done, defined at C:\Users\xyy82\AppData\Roaming\Python\Python36\site-packages\vpython\no_notebook.py:154> exception=TypeError('must be real number, not NoneType',)>
Traceback (most recent call last):
  File "C:\Users\xyy82\AppData\Roaming\Python\Python36\site-packages\vpython\no_notebook.py", line 187, in onMessage
	await loop.run_in_executor(None, GW.handle_msg, msg)
  File "C:\Program Files\Python36\lib\concurrent\futures\thread.py", line 56, in run
	result = self.fn(*self.args, **self.kwargs)
  File "C:\Users\xyy82\AppData\Roaming\Python\Python36\site-packages\vpython\vpython.py", line 393, in handle_msg
	cvs.handle_event(evt)
  File "C:\Users\xyy82\AppData\Roaming\Python\Python36\site-packages\vpython\vpython.py", line 3159, in handle_event
	evt['pos'] = list_to_vec(pos)
  File "C:\Users\xyy82\AppData\Roaming\Python\Python36\site-packages\vpython\vpython.py", line 177, in list_to_vec
	return vector(L[0], L[1], L[2])
  File "vpython/cyvector.pyx", line 29, in vpython.cyvector.vector.__init__
TypeError: must be real number, not NoneType

[BruceSherwood]

I verify seeing this error. As you imply, the bug appears only if zooming by touching the screen, not if using a mouse or touch pad. No idea what the cause is.

[BruceSherwood]

I verify that the same bug occurs with GlowScript VPython, so it is a problem with the GlowScript library, not with the Python code.

[bewantbe]

Should I file another bug in vpython/glowscript? Note that all I know about glowscript is it's the backend of the vpython, actually I don't even know how to reproduce this bug directly in glowscript.

I use touch screen often, so fixing this bug would have a great help to me.

PS: it is very nice to see that vpython is now again as easy to use as the old python module visual. Thank you for your works.

[BruceSherwood]

No need to file another report.