[WebView2SampleWinComp] Reentrancy issue when printing from context menu or “ctrl + p”

[franzi-ko]

Description

Running our WebView2 application using Visual Studio triggers a breakpoint when Windows save dialog is shown upon JavaScript print call. Crash won’t occur if no debugger is attached. Bug is reproducible with WebView2SampleWinComp when printing from context menu or “ctrl + p”.

Version
SDK: 1.0.1722.45
Runtime: 114.0.1823.58
Framework: Win32
OS: Win10

Repro Steps

• Start WebView2SampleWinComp from VS
• Open context menu and click “Print” or use “ctrl + p” directly
• Print preview dialog opens
• Select “Save as PDF”
• Save dialog opens
• Wait around 20 seconds until breakpoint is triggered with the following error message:

"Running a message loop synchronously in an event handler in Webview can cause reentrancy issue. Please refer to https://docs.microsoft.com/en-us/microsoft-edge/webview2/concepts/threading-model#re-entrancy for more information about threading model in WebView2 and how to enable native code debugging for this scenario."

Bug was not reproducible with WebView2APISample.

AB#45258108

[novac42]

Thanks for reporting the issue. I've assigned a dev to help look into this.

[vickiez]

Hi @franzi-ko, this sounds like a bug in our sample app - we'll investigate and get back to you. Are you able to repro the issue consistently?

[franzi-ko]

Hi @vickiez, thanks for investigating. I doubt that it is only a bug in the sample app as the same bug is reproducible with our WebView2 application. Please find the call stack of both the sample app and our app attached.

Yes, I can reproduce the bug consistently.

[JosephJin0815]

Hi @franzi-ko,
I don't see this reentrancy issue.

I've ran WebView2SampleWinComp in debug mode in Visual Studio with
Runtime: 114.0.1823.86
SDK: 1.0.1722.45 or 1.0.1823.32

Each time I can get the PDF downloaded immediately. Also there's no breakpoint triggered with several minutes' waiting.

Does this issue still exist in your webview2 application? If so, can you switch newer version of runtime and SDK which I've provided?

[franzi-ko]

Hi @JosephJin0815,

I switched to the newer version of runtime and SDK like you suggested. I can still consistently reproduce the bug.

It is important that you don't download the PDF immediately. You need to wait around 20 seconds with the Windows Save dialog being open. The breakpoint is triggered by the Save dialog which seems to be opened synchronously instead of asynchronously.

[castorix]

Same bug when dragging anything above other apps (like Google logo or text), after a few seconds (Runtime 143.0.3650.96)