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This isn't a question about implementing LTI, but rather, observed behavior in Canvas. Our institution has a home-grown LTI tool that serves thousands of LTI launches in Canvas every day without issue. But very occasionally and inconsistently, the LTI tool will run into an error where the LTI POST parameters sent from Canvas are not present on launch. This happens maybe a few times across thousands of launches, and it's happening for LTI embeds that are otherwise fully operational. I can see from our error logs that Canvas sends a POST request with no parameters to our LTI endpoint, for a student who had previously had a successful LTI launch in the same session, and when the student refreshes the page, the next LTI launch is valid and works. It tends to just happen once for a user rather than be repeated behavior, so I'm doubtful that this issue is being caused by the user, but it's always a possibility. Has anyone else observed this behavior? Is this something that could maybe be caused by peculiar user behavior, or is it just the occasional flake-out from Canvas? Is there anything I can do to prevent this error? It's a little concerning to me that an empty launch can happen, and that it happens so inconsistently, which makes it nearly impossible to debug. Thank you! ... View more

Just about every API call that I need to make a quizzing app is working, except for the one to answer questions. I'm using the following API call: Canvas LMS REST API Documentation My first question is: which ID should I use for the submission and for the quiz questions that I am submitting? In the QuizSubmission object, there is both an id and a submission_id. In the QuizQuestion object, there is both an id and assessment_question_id. The API documentation does not explicitly specify which of these myriad IDs to use. Which ID should I use for submissions and which ID should I use for quiz questions? Beyond that, I have tried every permutation of quiz/submission ID possible and am still getting an error back from the API. I get an error_report_id in the response, but I see no documentation anywhere about how to access an error report. I was able to find a related thread on the google forums (Google Groups ), but the route for /error_reports/id that was specified there results in an error saying that I don't have permissions to access the page. Even the highest-level admin for our Canvas instance runs into the same permissions error. Does anyone know of a way to see the error reports? Depending on which permutation of quiz/submission ID that I send to the API, the error that I get is either "The specified resource does not exist" or "internal_server_error." Neither of which is very helpful for solving my problem. Considering that this is the only API call that I've had to make so far with a nested array (for the question IDs and answers), that might be the issue (or a red herring...). I'm using PHP and cURL for my API calls, and using http_build_query() for my post parameters, which theoretically should be able to handle the nested arrays without a problem. I'm pretty stumped on what the issue might be. Thoughts? Thank you! ... View more

I've run into a couple of issues with the height of SCORM assignments that are a pretty big impediment to the courses that I'm working on. 1) The .tool_content_wrapper height of the containing iframe in Canvas is often much too large for my SCORM content. It seems like Canvas is dynamically setting this number using javascript, and I was wondering where this number is coming from and if it could be made smaller. At the moment, there's such an exorbitant amount of whitespace beneath the content that it appears to students that content is missing from the page that wasn't loaded properly. 2) Dovetailing into the first issue is that, although I am successfully able to send a postMessage to Canvas to resize the iframe to the SCORM content's actual height (allow external tool to resize iframe · instructure/canvas-lms@834aba7 · GitHub ), the content area is not being repainted after my postMessage is sent. This is a little tricky to explain, but I'll do my best. Going back to my first point, the original size of the iframe is much too large. So, inside of the html page I'm serving my SCORM content on, I've sent a postMessage to Canvas after my content has loaded, to set the height of the containing iframe for my content. The containing iframe successfully changes to the proper size. However, the larger space that the iframe originally took up does not get repainted. There's a large expanse of whitespace beneath the SCORM frameset where the original iframe was originally painted. I don't seem to have this issue with any LTI tools I've created or used, but maybe I've just been lucky. I know that SCORM is technically being served in an LTI wrapper. I'm curious if the issue might have to do with SCORM being served in a frameset instead of just an iframe, like an LTI tool, or if there's some other issue at play that Canvas could potentially fix. As an example, here's a screenshot of what I'm talking about with the whitespace not being repainted. Just to make the issue super clear with a bit of an exaggeration, I uploaded a SCORM package where the height I'm sending in the postMessage is just 30px. The sliver of dark blue in the screenshot is my SCORM tool. Yet the height of the content area is still huge, from where the iframe/frameset was originally painted. (And just to anticipate a possible question...yes, the height that is painted here in the content area is not due to the min-height of 450px for #main. I can see in dev tools that the whitespace that appears is much taller than 450px.) This vast expanse of whitespace is obviously an issue for the look of the page. It might not always be as exaggerated as my example, but I've had issues with run-of-the-mill SCORM exports where hundreds of pixels of whitespace was appearing that should not be there. This seems like more of an issue for Canvas than something that I could fix on my end, but if anyone has ideas, I'd sure appreciate it. Thank you! ... View more