Feature Request - Add the ability to automatically merge `enable-features/disable-features` command-line args with existing values

[SLT-World]

Is there an existing issue for this?

• I have searched both open/closed issues, no issue already exists.

CefSharp Version

147.0.10

Operating System

Windows 11

Architecture

x64

.Net Version

.NET 8.0

Implementation

WPF HwndHost

Reproduction Steps

• Configure CefSharp to use the Chrome runtime style: CefSharpSettings.RuntimeStyle = CefRuntimeStyle.Chrome;
• Add a disable-features command-line argument, any value will crash the application: CefCommandLineArgs.Add("disable-features", "GlobalMediaControls");
• Initialize CEF.
• Create a ChromiumWebBrowser instance.
• Crash observed.

Made a minimal reproducable repository demonstrating this issue: https://github.com/SLT-World/CefSharpRuntimeCrash/blob/main/MainWindow.xaml.cs

Expected behavior

The browser should not crash when using Chrome runtime style together with the disable-features flag.

Perhaps related, the supplied disable-features list should be merged, similar to the behavior observed in cefclient.exe in Other information below.

Actual behavior

When using the Chrome runtime style, adding any value to disable-features causes the application to crash during browser creation.

Issue appears to be specific to the Chrome runtime style and does not occur when using the Alloy runtime style. App manifest does not have an effect.

Additionally, the disable-features list are not merged correctly with an existing list. There are 2 completedly separate disable-features.

Regression?

Unsure.

Known Workarounds

Avoid using the disable-features flag when running with the Chrome runtime style.

Using Alloy runtime style avoids the crash entirely, even with the disable-features flag.

Does this problem also occur in the CEF Sample Application

No

Other information

I was unable to replicate the issue with cefclient.exe on the same version 147.0.10 so I believe this may be a CefSharp issue.
I used the following command: cefclient.exe --multi-threaded-message-loop --no-sandbox --enable-chrome-runtime --disable-features=GlobalMediaControls.
I can assure that cefclient was running in Chrome runtime style as the chrome://extensions page exists.

Furthermore, in cefclient.exe, GlobalMediaControls is merged as --disable-features=GlicActorUi,AutofillActorMode,LensOverlay,GlobalMediaControls, seen in chrome://version.

The existing disable-features seems to originate from https://github.com/chromiumembedded/cef/blob/58fa5d380aeaf56691ed5652ccec9386a7cc7d19/libcef/common/chrome/chrome_main_delegate_cef.cc#L357

Unfortunately, I lack the skills to further investigate or debug it myself beyond this point.

[voidmaster000]

Cannot replicate it on my side.

[amaitland]

Furthermore, in cefclient.exe, GlobalMediaControls is merged as --disable-features=GlicActorUi,AutofillActorMode,LensOverlay,GlobalMediaControls, seen in chrome://version

CEF doesn't provide a public API to my knowledge that allows for merging. You can ask on https://www.magpcss.org/ceforum/index.php for a second opinion.

You need to load the browser, get the features that are already disabled, then include those in your disable-features.

Additionally, the disable-features list are not merged correctly with an existing list. There are 2 completedly separate disable-features.

Last one should win. So you need to have your disable-features include all the ones that CEF has already disabled.

I was unable to replicate the issue with cefclient.exe on the same version 147.0.10 so I believe this may be a CefSharp issue.

Based on the information provided I don't believe this is a bug in CefSharp.

[SLT-World]

You need to load the browser, get the features that are already disabled, then include those in your disable-features.
Last one should win. So you need to have your disable-features include all the ones that CEF has already disabled.

Thank you very much, this resolved the issue.

It appears that the crash was caused by GlicActorUi not being included in my disable-features list.
Including GlicActorUi like so prevented the crash when using the Chrome runtime style.

Settings.CefCommandLineArgs.Add("disable-features", "EnableHangWatcher,GlicActorUi,AutofillActorMode,LensOverlay,AnyOtherFlagHere");

Perhaps CEF's disable-features is overridden when there's 2 disable-features, so I encountered the crash when I only supplied GlobalMediaControls to disable-features.
It would be ideal for CefSharp to somehow merge CEF's disable-features automatically to prevent any future issues similar to this, but it works for the time being.

[amaitland]

It would be ideal for CefSharp to somehow merge CEF's disable-features automatically to prevent any future issues similar to this, but it works for the time being.

I don't remember CEF providing an API for removing a switch, looks like there is now

https://cef-builds.spotifycdn.com/docs/147.0/classCefCommandLine.html#a82dac176ee3b7a2d1e08731871e7e768

So this maybe possible, though automatically merging would remove the ability to replace what is there if you didn't like the defaults, so that would need to be configurable.

So we might be able to implement something.

CefSharp/CefSharp.Core.Runtime/Internals/CefSharpApp.h

Line 210 in fd87988

if (kvp->Key == "disable-features" || kvp->Key == "enable-features")

I'll reopen this issue to track that work.

[amaitland]

We could add CefSharpSettings.MergeFeaturesCommandLineArgs with a default to true to allow users to opt out.

If key exists, then get it's value, remove it, merge in the user supplied args.

[SLT-World]

Submitted a pull request #5245 which should include the appriopriate changes, CefSharpSettings.MergeFeaturesCommandLineArgs and merging.

I was able to build and modify CefSharp after much difficulty.
Encountered and resolved an unclear duplication issue with the merging.
Successfully tested with some local modifications in CefSharp.Wpf.HwndHost.Example, not included in the PR.

[SLT-World]

In regards to the duplication issue, it appears that disable-features is processed twice during merging?

The following is only an example for debugging, not included in the PR:

if (kvp->Key == "disable-features" || kvp->Key == "enable-features")
{
    if (CefSharpSettings::MergeFeaturesCommandLineArgs)
    {
        CefString existingValue = commandLine->GetSwitchValue(name);
        if (existingValue.empty())
        {
            commandLine->AppendSwitchWithValue(name, value);
        }
        else
        {
            commandLine->RemoveSwitch(name);
            commandLine->AppendSwitchWithValue(name, StringUtils::ToNative(StringUtils::ToClr(existingValue) + ",|," + kvp->Value));
        }
    }
    else
    {
        commandLine->RemoveSwitch(name);
        commandLine->AppendSwitchWithValue(name, value);
    }
}

settings.CefCommandLineArgs.Add("disable-features", "GlicActorUi,GlobalMediaControls,Test,EnableHangWatcher");
CefSharpSettings.MergeFeaturesCommandLineArgs = true;

This causes chrome://version to display:

--disable-features=EnableHangWatcher,GlicActorUi,AutofillActorMode,LensOverlay,|,GlobalMediaControls,Test,|,GlicActorUi,GlobalMediaControls,Test,EnableHangWatcher

Based on the ,|, separators, the merge logic seems to executes twice.
The first time is properly de-duplicated after AppendSwitchWithValue.
The second time is not de-duplicated.

I am unable to differentiate the second time in the code, so the current PR workaround prevents duplication by relying on a string-based list check.

For optimization, some modifications could probably be made to reject the unnecessary second time, therefore removing the extra processing of a string-based list check.
But sadly that is beyond my C++ knowledge.