Troubleshooting Equation Images
webwork2/lib/WeBWorK/Constants.pm). After that, you should see directories like
ImageGenerator.xxxxxx accumulating in
webwork2/tmp/. These contain files that ImageGenerator uses in generating each equation image:
equation.tex- TeX source file
equation.log- log file written by LaTeX
equation.dvi- DVI file generated by LaTeX
latex.err- messages written to STDOUT and STDERR by LaTeX
dvipng.err- messages written to STDOUT and STDERR by dvipng
latex.errdon't exist, this indicates that LaTeX was never invoked. I'm not sure what would cause this.
equation.logdoesn't exist, then LaTeX was invoked, but probably never ran. Check for a properly installed
latexand make sure that the path to
latex.errfor errors. These might indicate problems in the TeX code being sent to LaTeX for processing. The errors might be in the equation itself in the PG file, or in the TexPreamble or TexPostamble, which are defined in
equation.dvidoes not exist, then LaTeX was not able to interpret its input successfully. Read
equation.dviin a DVI viewer and see if it contains a properly rendered equation.
The PNG file that
dvipng produces is moved from the
ImageGenerator.xxxxxx directory and renamed, so you'll have to look at the HTML source of the problem page to find its name. It'll be something like
e40d5b21c65856b95bbc6f4dfced571.png. (That's the SHA-1 hash of the TeX equation followed by
1.png.) Make sure that file exists in
webwork2/htdocs/tmp/equations/. Check its permissions. Make sure it is web-accessible (check
http://yourserver/webwork2_files/tmp/equations/filename.png). See if it's a valid PNG, and see if it contains the proper equation image.
Inappropriate ioctl for device
This seems to occur when very old versions of
dvipng are in use, and the easiest way to resolve it is to upgrade to the latest version. If that is not possible, try the following:
[In ImageGenerator.pm I] had [to] use the command my $dvipngCommand = "cd $wd && $dvipng " . $DvipngArgs . " equation.dvi > dvipng.out 2> dvipng.err"; i.e. pass it equation.dvi rather than equation. Probably my old version of dvipng requires this. There certainly can't be any harm in this, correct? The newer versions of dvipng must accept this, correct?