We use the WPF EO component as the user interface for a line-of-business application (currently using 21.2.47, as delivered by Nuget).

The application is wrapped in an installer using WiX.

We see that sometimes (but not all the time), after the first install of the application the web page fails to load.

i.e. we do:
webControl.WebView.Url = newUrl;

where newUrl is a locally held file ("i.e. file:///C:/Program%20Files/path/to/our/html/file.html").

We then never see any LoadCompleted or LoadFailed event. If we close the app (Alt-F4) and launch it again, it works as expected.

If I install with the Debugger enabled (i.e. ShowDebugUI of true), I can see the WebView instance and within the Chrome Debugger I can see the HTML page has been loaded. No errors are listed in the console.

Doing a window.location.reload or F5 within the debugger seems to cause Chrome to refetch the HTML/CSS/JS, but we still never get a LoadCompleted or LoadFailed event.

Any tips about how to go about debugging this?

What is the internal logic that triggers the LoadCompleted or LoadFailed events?

Sorry, last post for now.

Looking at document.readyState using the Chrome Debugger console shows "complete"

Thanks, I'll attempt to produce a test case, though this may be tricky.

In the mean time, I've done some more investigation.

We were using the LoadCompleted callback to trigger the application to move to the next stage of initialization (i.e. we wait until the browser has fully finished loading, then we pass it a chunk of "configuration" JSON to finish the process).

I've now amended this, so instead, we invoke some JavaScript when the browser fires windows.OnLoad() (rather than waiting for LoadCompleted). This JavaScript then invokes a function registered with RegisterJSExtensionFunction.

We seem to always get this invocation on the C# side, so I believe the browser always completes loading. In this modified code, we then use QueueScriptCall to pass the "configuration" JSON back to the browser (as we can't EvalScript from within a callback registered with RegisterJSExtensionFunction). However, this QueueScriptCall sometimes fails (or at least, doesn't get invoked).

I'm assuming that whatever is blocking the LoadCompleted from firing is also causing whatever has been queued by QueueScriptCall to not run.

What is the logic behind LoadCompleted (as it seems to be more than just repeating windows.onLoad())? Is there any linkage between LoadCompleted not firing and JavaScript enqueued using QueueScriptCall being blocked?

I'm beginning to wonder if I have a stray call to QueueScriptCall prior to getting the LoadCompleted event. Is it valid to call QueueScriptCall prior to LoadCompleted or could this be causing the issue I'm seeing?

Thanks for the information :)

I found that, under rare circumstances, we may queue some JavaScript using QueueScriptCalls very early in the loading process (i.e. before LoadCompleted had fired).

Having put protection around this (so we only queue up JavaScript after getting LoadCompleted), we are no longer seeing an issue.

We have logging attached to LoadFailed and were never seeing that get called. It feels like there is some interaction between the Loader and script engine, if we enqueue script calls while the load is in progress.

I'll try and simulate this by performing some QueueScriptCalls while loading is occurring and see if I can get it to reliably fail (i.e. no LoadCompleted or LoadFailed)

Thanks for the additional information. What do you do in your QueueScriptCall? Does the problem occurs if you do something "harmless" like QueueScriptCall("var i = 0;")?

The issue still occurs with QueueScriptCall("var i = 0;").