WeBWorK Problems

Graphics won't load

Graphics won't load

by Tamara Lakins -
Number of replies: 3

I've had several students who report that the plots in my webwork assignments are not loading.  I am attaching a screen shot so you can see what's happening.  Here are the URLs for some of these problems:




I have advised students to use the latest version of Chrome or Firefox as their browser.  Two of the students experiencing this problem reported that they are using Windows 10.  I am using webwork on a MacBook Air using firefox, and the graphics load fine for me.

Thanks in advance for any ideas you may have for fixing this problem.

Attachment hw2screenshot.png
In reply to Tamara Lakins

Re: Graphics won't load

by Danny Glin -

I believe that the issue is that the MAA server is configured to use SSL to serve pages securely (i.e. using https), but the image files are being sent insecurely (i.e. using http).  Some browsers are more strict than others about viewing pages that have a combination of secure and insecure elements, and it looks like Chrome is refusing to load images in a secure page if the images are not sent securely.

I was able to reproduce this behaviour with Chrome, while Safari didn't complain.

I have reported the issue to the MAA.  Hopefully they will be able to fix it.

In reply to Danny Glin

Re: Graphics won't load

by Sean Fitzpatrick -

I just ran into this on my server: graphics were loading fine until a couple of weeks ago, but this week we discovered they were being blocked.

The relevant lines in localOverrides.conf look like something that was leftover from an older version of WeBWorK (there's no way that it would have occurred to me to server images using a different port). Commenting them out has fixed the problem.

What I had:

$webworkDirs{htdocs_temp}  =  '/var/www/html/wwtmp';
#$webworkURLs{htdocs_temp}   = '/wwtmp';
$webworkURLs{htdocs_temp}  = 'https://webwork.uleth.ca:8443/wwtmp';
$webworkDirs{equationCache} = "$webworkDirs{htdocs_temp}/equations";
$webworkURLs{equationCache} = "$webworkURLs{htdocs_temp}/equations";
$courseDirs{html_temp}  =  "/var/www/html/wwtmp/$courseName";
#$courseURLs{html_temp}   = "/wwtmp/$courseName";
$courseURLs{html_temp}   = "https://webwork.uleth.ca:8443/wwtmp/$courseName";
# Location of MathJax script, used for the MathJax display mode.
#$webworkURLs{MathJax}       = 'https://webwork.uleth.ca:8443/webwork2_files/mathjax/es5/tex-chtml.js';

But I tried using the defaults in localOverrides.conf.dist, and that doesn't work either.

Does anyone have any insight on the correct configuration when using SSL? (Maybe this would be solved by a wildcard certificate, but let's assume that's not an option.)