Parent Page Reload From LTI

[aday]

Hi,

I am trying to force the parent page to reload from the LTI

We have some functionally in our LTI that hides and shows some menu items in a course when it is run.

When the process is done I would like to refresh the parent page so update the menus.

I have tried 

 parent.postMessage(JSON.stringify(
        {
            subject: "lti.pageRefresh"
        }), "*");

and I get no errors but nothing happens. Am I doing this wrong or is refresh a page not supported (I thought I read that it was)

Any ideas?

[matthew_buckett]

The documentation for the window postMessage support is at: https://canvas.instructure.com/doc/api/file.lti_window_post_message.html

I can't see any reference to supporting `lti.pageRefresh` messages there. I don't think you can use plain JS to do this because of cross origin restrictions, your LTI tool will be considered to be in a different origin to Canvas and so blocked.

Ways around this:

• Add a listener for a custom postMessage object that reloads the current window, this should be added to the JavaScript for the Canvas theme. Then in your LTI tool send the custom messages.
• Pass across enough information in LTI variables so you can calculate the current Canvas URL (eg if you only support the course placement then Canvas.externalTool.global_id, Canvas.api.domain, Canvas.course.id should be enough) then do `window.top.location = 'https://inst.instructure.com/courses/1234/external_tools/5678'` and that should reload the LTI tool.

It would be good if this was supported fully by Instructure without hacks like this.

[matthew_buckett]

Alternatively if you are happy for the user to leave your LTI then redirecting them to the LTI return URL (supplied in both LTI 1.1 and 1.3 launch parameters by default) will cause the page to reload and so show the updated course menu items.