Fix feedback previews when the display mode is "images".

[drgrice1]

Currently if the display mode is "images", then the student and correct answer previews don't work. The images are never actually rendered, thus the image files are never created, and so the alt value is shown which is the original TeX for the answer. The reason for this is that the image generator runs before the post content processor runs. So equation images in the problem are rendered, but not those in the feedback. That was done because of the hack of inserting the string MaRkEr followed by the image number hash when the image is initially inserted into the problem text, and then later replacing that with the alignment styel when the image is rendered. That results in invalid HTML which Mojo::DOM doesn't like.

To fix the issue the MaRkEr hack is reworked. Instead of that string, a data-imagegen-alignment-marker attribute is used whose value is the image number hash. Since that is valid HTML, Mojo::DOM is fine with it and leaves it as it is. So the image generator can now be run after the post content processor runs, and that renders the images in feedback as well.

Care is needed for the images in feedback when the data-imagegen-alignment-marker is replaced. Since the rendered img tag is inside the data-bs-content attribute of the feedback button, it is HTML encoded. So instead of double quotes, the HTML double quote escape character (") is used.

Another option would be to eliminate the "images" display mode. Clearly no one is using it, since I think this bug would have been noticed rather quickly when WeBWorK and PG 2.19 were released if anyone was using it.

[somiaj]

Aren't images for formulas also going to have accessibility issues? This could be another reason to drop support for them.

[drgrice1]

The images do provide an alt attribute. The alt attribute is the LaTeX that is used to generate the equation. That may not be very good, but it is something.

[pstaabp]

I think removing images would be fine. Are there any reasons for anyone to use images?

That being said, shouldn't the images setting in the Display Settings of the User Settings switch this?

I did this and MathJax still shows up. I had to uncheck MathJax in the Course Configuration to get images to display.

That being said, this does fix the problem.

[drgrice1]

When you change the "Display Settings" from the "User Settings" page, it does change the display mode that is used. However, there are some cases where the previous setting will persist after you make that change. For example, if you have a problem open in one tab and have navigated around using page links (so that the displayMode URL parameter is added), and then open the user settings in another tab, then the setting in the prior tab will stay with the old setting because the displayMode URL parameter is overriding the database setting.

[somiaj]

I am still in favor of removing images display mode altogether, but this is a good fix and we can decide about removing this at a later time.

[drgrice1]

Yeah, I think it would be good to leave the image generator in working order before we remove it!