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Weird rendering problem occasionally

Weird rendering problem occasionally

by Wesley Burr -
Number of replies: 7
Hi, all,

My GoogleFu has failed me, and I can't find anyone else this has applied to. We're running ~ 600 quizzes per week in WeBWorK, and in the last two weeks I've had two students who've had questions not render properly. Refreshing / logging back in doesn't seem to work. It's a gateway/quiz setup, 15 minute limit. They've both seem something like the attached image, where all the options of the multiple choice are replaced by "[math]".

In the second case, I know the student's details: he was running the latest version of Google Chrome on Mac OSX 10.12. I don't recall the first time it happened.

Unfortunately, with the randomization of questions, it's hard to be able to tell what the solutions for a given student should be, so I've just overwritten the score for these two students. I'd like to figure out what's going on, though, so I can fix it in general, or at least have a workaround for the TAs to use.

Any thoughts?


Attachment ww_render.jpg
In reply to Wesley Burr

Re: Weird rendering problem occasionally

by Wesley Burr -
The problem that rendered weirdly is attached. Nothing odd that I can see, and it worked for the other 599-odd students.
In reply to Wesley Burr

Re: Weird rendering problem occasionally

by Danny Glin -
Does it render properly when you act as the student and view the problem? If so, it's probably at least partly related to the browser.

This happens to me every once in a while, and usually refreshing the page fixes it. I suspect that in the cases I've seen it has been a result of the connection being interrupted while MathJax is being loaded. I think I've seen the same thing when the page load times out before MathJax is loaded.

If refreshing doesn't work, try holding down "shift" and refreshing the page. This forces a reload of not only the page itself, but all the dependencies including the javascript.
In reply to Danny Glin

Re: Weird rendering problem occasionally

by Wesley Burr -
It does appear fine for me, and fine for the majority of the students in the class. The forced-reload is a good suggestion. I'll pass it on to my TAs and see if it fixes the problems in future.

I can always try Paul's suggestion of just using rendered images as well, although the MathJax is nicer if it can be reliable.
In reply to Wesley Burr

Re: Weird rendering problem occasionally

by Davide Cervone -
Are the students using their own computers, or are they campus-owned ones? If it is their own, they may have disabled javascript (e.g., via a "NoScript" plugin). That would prevent MathJax from running. Some browsers also allow javascript to be turned of in their preferences.

Finally, if neither of those is the problem, try opening the browser console window (on the Mac, use command-C to open the console) and see of there are any error messages there. If not, type in

MathJax.Message.Log()

and see if there are any error messages there. These might give you a hint about what is happening.
In reply to Davide Cervone

Re: Weird rendering problem occasionally

by Wesley Burr -
They're using their own laptops. And I often don't have access to them in the moment (they're at workshops with the TAs). Thanks for the hint about checking to see if MathJax is erroring: it's a good thought.
In reply to Wesley Burr

Re: Weird rendering problem occasionally

by Paul Pearson -
Hi Wesley,

Here's a temporary fix: switch the display mode from "MathJax" to "Images" in the course configuration. MathJax is rendered in the client's browser, while images are generated on the server and delivered to the client.

Also, I've had the same problem, would like to know why MathJax is doing this, and would like to know other solutions to this problem.

Best regards,

Paul Pearson
In reply to Wesley Burr

Re: Weird rendering problem occasionally

by John Travis -
I believe this is due to the order in which the page is fetched and the MathJax fonts are fetched. If the page gets there first, then this could happen. Most of the time the math gets inserted eventually. If you reload the page, it should work (at least that appears to work for me.)