Noticed in Mahara 1.10; testing on 15.04 and 15.10 needed:
When a page contains many embedded PDFs, the following can happen (all at once):
- some PDFs are displayed
- others show an error message
- others show a Mahara login box
- you can be logged out completely
An initial investigation couldn't replicate the issue successfully and it seemed to happen intermittently. From what we gathered, it seems to be a rendering / loading / overloading issue: Too many instances of pdf.js try to be loaded at the same time causing timeouts and other weird behavior.
I see two possibilities:
1. Limit the number of PDFs that can be embedded on a page
2. Load PDF blocks progressively one after the other
I don't know if the second option would mitigate the problem or not. The first one could be limiting user's creativity, but would prevent endless waiting for a page to load with the content.
Further insight is needed before a final decision can be made on how to continue from here.
This does indeed sound like a rendering issue with too much browser resource being taken up to handle the pdfs. I suspect the bigger the pdf the more resources it will take to render.
So having 6 small pdfs may work fine but 3 big pdfs fail as each page of the pdf takes resources to render.
So it might be easiest to have a warning in the pdf configuration form warning about the resource intensiveness.