CefBrowserHost::CreateBrowser call failed when trying to reuse BrowserSettings instance

[PitySOFT]

• What version of the product are you using?

  • Nuget 71.0.0

• What architecture x86 or x64?

  • x86

• On what operating system?

  • Win 8 and Win10

• Are you using WinForms, WPF or OffScreen?

  • WPF with WindowsFormsHost

• What steps will reproduce the problem?

  • I have two instances of CefSharp with different CefSettings, because I can't change the settings on runtime. Depending on some data I choose what instance to show. Till version 71.0 the code where si make the swap between those two instances works great. But with version 71.0 it breaks with the exception attached below.

  • I try to set the Child of a WindowsFormsHost with an instance of a ChromiumWebBrowser with the following code MyFormsHost.Child = my ChromiumWebBrowser;

• What is the expected output? What do you see instead?

  • The application crashes because on unhandled exception.

• Please provide any additional information below.

  • System.InvalidOperationException
    HResult=0x80131509
    Message=CefBrowserHost::CreateBrowser call failed, review the CEF log file for more details.
    Source=CefSharp.Core
    StackTrace:
    at CefSharp.ManagedCefBrowserAdapter.CreateBrowser(IWindowInfo windowInfo, BrowserSettings browserSettings, RequestContext requestContext, String address) in c:\projects\cefsharp\cefsharp.core\managedcefbrowseradapter.cpp:line 29

  • The debug.log file is empty

• Does this problem also occur in the CEF Sample Application from.

  • The examples are not relevant to this because I used 2 instances of CefSharp

[amaitland]

Can you please fork https://github.com/cefsharp/CefSharp.MinimalExample and provide an example that reproduce your problem.

Using the WinForms version in a WPF app using WindowsFormsHost works as expected for me.

Without an example that actually reproduces your problem there is anything I can do.

[amaitland]

@PitySOFT Are you able to provide an example that reproduces your problem? I'll be releasing 71.0.1 bug fix packages in a few days, if you can provide an example in the next 48hrs I'll see if this is fixable, otherwise it'll have to wait for the next major release.

[PitySOFT]

Hi, didn't had time to make the example. I will come back with it when I'm ready to reproduce. Please release the 17.0.1 don't wait for me. Thanks.

[PitySOFT]

Hi,

I manage to reproduce the crash in a minimal project.

You have the project here.

Binary file removed

With Cef 69.0.0 will work fine, but using 71.0.0 will crash.

[merceyz]

No binary files, fork the minimal project instead and provide that as a link

[PitySOFT]

This is ok?

https://github.com/PitySOFT/CefSharp.MinimalExample

[merceyz]

Yes, thank you.

The issue is you're reusing the browser settings, the settings are disposed of after the browser is created at:

CefSharp/CefSharp.WinForms/ChromiumWebBrowser.cs

Lines 649 to 653 in 6f6ca94

	if (browserSettings != null)
	{
	browserSettings.Dispose();
	browserSettings = null;
	}

This was added in 4a41fdf for WinForms

[amaitland]

Reusing browser settings is problematic, so making them single use only.

Need an additional check and throw exception if they're disposed, will add that shortly..

Thanks for taking the time to reproduce 👍

[merceyz]

The OffScreen version already checks this[1], seems the check is missing for WPF and WinForms

1:

CefSharp/CefSharp.OffScreen/ChromiumWebBrowser.cs

Lines 382 to 385 in 6f6ca94

	else if(browserSettings.IsDisposed)
	{
	throw new ObjectDisposedException("browserSettings", "The BrowserSettings reference you have passed has already been disposed. You cannot reuse the BrowserSettings class");
	}

[amaitland]

Now that browser creation is common between WPF, informs and OffScreen checks can be made in

CefSharp/CefSharp.Core/ManagedCefBrowserAdapter.cpp

Line 26 in 6f6ca94

if (browserSettings == nullptr)

In WinForms it might make sense to remove the setter for browser settings.

Will provide full analysis for discussion when I am in front of a computer

[PitySOFT]

Thanks for information, I confirm that not using the same BrowserSettings works.

For the same example code I have some issues with onscreen keyboard for touch screens. I know that it's hard to test because the lack of the touch screens but maybe you can check something in the code.

On CefSharp 65.0.1 the keyboard works perfect, but:

• on 67.0.0 when the onscreen keyboard appears the sides of the keyboard are transparent but after a short period the sides becomes white.
• on 69.0.0 and 71.0.0 keyboard appears with transparent on sides, then this becomes white and then the keyboard will disappear.

I can provide videos for all situations.

[amaitland]

Any problems with the onscreen keyboard would need to be fixed in CEF/Chromium, see https://github.com/cefsharp/CefSharp/blob/master/CONTRIBUTING.md#cefsharp-vs-chromium-embedded-frameworkcef

[amaitland]

Firstly it's possible to reuse a CefBrowserSettings instance, it's just a struct, the problem lies with the BrowserSettings wrapper and how we control the freeing of unmanaged resources. Typically I've taken the approach to be fairly aggressive with cleaning up resources, occasionally this makes things harder to use, reduces the likeliness of hard to track down memory leaks. (CEF has just made some improvements for tracking down stray references, hopefully this improves things going forward, see https://bitbucket.org/chromiumembedded/cef/issues/2593/improvements-for-debugging-cefrefptr).

Every so often I would see users attempting to reuse a BrowserSettings instance in the following scenario.

• Create BrowserSettings
• Assign to ChromiumWebBrowser
• Dispose of ChromiumWebBrowser
• Assign BrowserSettings to new ChromiumWebBrowser instance, browser creation fails (slightly different set of steps to reproduce, same outcome as this particular issue).

My initial reaction was to simply things and just have a one to one mapping of BrowserSettings to ChromiumWebBrowser instance.

How important is it to reuse a BrowserSettings instance? Open to discussion on this one. We can remove the Dispose calls from the browser and rely on the User/Garbage Collector to handle the object, it's a wrapper around a every basic struct, doesn't hold any external references, so the GC should deal with it nicely, unlike other objects, having it leak won't stop CEF from shutting down properly. So perhaps the simplest and most flexible option is to remove all these additional checks and Dispose calls?

[amaitland]

Having through about it I'm think of removing the restrictions and remove the code to Dispose of the BrowserSettings from the ChromiumWebBrowser instances. Will rely on GC/User to Dispose of the BrowserSettings object.

[amaitland]

Ended up going with what I think should be a happy medium. If CefSharp creates the BrowserSettings instance for you then it will automatically be Disposed. If you create the BrowserSettings instance yourself then either call Dispose explicitly or let the GC collect the object.

Changes were made to WPF, WinForms and OffScreen so they are now all consistent. Passing an already Disposed instance of BrowserSettings to the underlying CreateBrowser method will result in an ObjectDisposedException.

[merceyz]

Changes were made to WPF, WinForms and OffScreen so they are now all consistent

@amaitland Any reason it wasn't implemented in the underlying CreateBrowser method?

[amaitland]

@amaitland Any reason it wasn't implemented in the underlying CreateBrowser method?

@merceyz Excellent suggestion 👍 Follow up commit d2d1e6f

Error message improved slightly.

[merceyz]

Excellent, however I was thinking it would be better to move all of it into that method. So that the same logic isn't repeated over all implementations

[amaitland]

Excellent, however I was thinking it would be better to move all of it into that method. So that the same logic isn't repeated over all implementations

What logic are you referring to?

[merceyz]

CefSharp/CefSharp.OffScreen/ChromiumWebBrowser.cs

Lines 401 to 404 in 86b2d8c

	if (browserSettings == null)
	{
	browserSettings = new BrowserSettings(frameworkCreated: true);
	}

This could be handled in the managedCefBrowserAdapter, meaning the new constructor and property can be removed

[amaitland]

This could be handled in the managedCefBrowserAdapter, meaning the new constructor and property can be removed

Yes it could. That wasn't the plan though. that would be a breaking change forcing users to always create BrowserSettings objects.

Code like https://github.com/cefsharp/CefSharp/blob/cefsharp/67/CefSharp.Wpf.Example/Views/BrowserTabView.xaml.cs#L28 would all of a sudden be a NullReferenceException.