WebView not displaying when applying AdditionalBrowserArguments

[RickStrahl]

I'm trying to apply browser arguments to preview auto-play behavior for media elements in the browser using the --disable-features startup flag.

I'm using the code like the following:

// must create a data folder if running out of a secured folder that can't write like Program Files
var browserFolder = Path.Combine(mmApp.Configuration.InternalCommonFolder, mmApp.Constants.WebViewEnvironmentFolderName);

var env = await CoreWebView2Environment.CreateAsync(
    userDataFolder: browserFolder, options:   new CoreWebView2EnvironmentOptions
    {
        AdditionalBrowserArguments = "--disable-features=\"PreloadMediaEngagementData, MediaEngagementBypassAutoplayPolicies\"", 
    }
);
await WebBrowser.EnsureCoreWebView2Async(env);

When I use this (or several other startup flags I've tried, my WebView control fails to initialize and I get a blank WebView canvas - the browser appears to not load. I also don't get an error or a trigger in the BrowserProcessFailed event.

I'm not sure whether I'm using the Arguments option correctly and haven't been able to dig up any examples.

Expected behavior

• Should work 😄

• If it fails should throw or have some indiciation on what failed

• WebView Control WPF (1.0.1901.177

• .NET 7.0

• Windows 11

[aluhrs13]

Are you listening to CoreWebView2InitializationCompleted (https://learn.microsoft.com/en-us/dotnet/api/microsoft.web.webview2.wpf.webview2.corewebview2initializationcompleted?view=webview2-dotnet-1.0.1901.177#microsoft-web-webview2-wpf-webview2-corewebview2initializationcompleted) at all? If there's a failure during initialization that's where it would show up.

If I had to guess based off what you've shared - Do you have a WebView2 already created with that userDataFolder, but with different AdditionalBrowserArguments?

[RickStrahl]

Do you have a WebView2 already created with that userDataFolder, but with different AdditionalBrowserArguments?

Yes. It's in Markdown Monster and it's the previewer which gets loaded after the editor both of which use a WebView (multiples).

Do they all have to be exactly the same? I thought that each instance is starting a new process...

I'll check into thte initialization event and see if I get more info.

[aluhrs13]

That's likely the problem, you'd see an initialization error of 0x8007139F (ERROR_INVALID_STATE) if that's the case. The table at the bottom of the docs for EnsureCoreWebView2Async mentions it.

As far as processes - Each WV2 creates a new renderer process, each UserDataFolder (UDF) creates a new browser process and AdditionalBrowserArguments essentially sets global state for the browser process. Every WV2 created with that UDF needs to have the same EnvironmentOptions / CreationProperties or it will fail. We chose to fail in this case since the AdditionalBrowserArguments can't/won't be respected due to the process already existing.

There is confusion around it sometimes and it's not perfect for every use-case - For your use-case, what would your preferred behavior be if we can't respect your EnvironmentOptions due to a conflict with existing processes? Some suggestions we've seen in the past include a setting to ignore the options if they differ, automatical create a new UDF (#3668), or somehow attempt to restart all the WV2s for the UDF.