[Webkit-unassigned] [Bug 233419] New: WKWebView microphone access not working on background

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=233419

            Bug ID: 233419
           Summary: WKWebView microphone access not working on background
           Product: WebKit
           Version: Other
          Hardware: iPhone / iPad
                OS: iOS 15
            Status: NEW
          Severity: Blocker
          Priority: P2
         Component: WebKit API
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: franz at taptanium.com

What's happening: We're loading a WebRTC-based mobile-optimized chat web app into WKWebView which allows users to toggle on their microphone and talk to others in a virtual room. The WKWebView gets added as a subview to the root view controller's root view. We also want camera access, but I'm focusing on getting the microphone to work correctly for now.

However, upon sending the app to the background, all audio as well as the microphone stops working.
Expected behavior: Audio and microphone continue to work as the user backgrounds the app.

Under "Signing & Capabilities", we're specifying these Background Modes:
+ Audio, AirPlay, and Picture in Picture
+ Voice over IP

The .entitlements file specifies:
  com.apple.security.network.client = 1
  com.apple.security.device.camera = YES
  com.apple.security.device.audio-input = YES

Side note: Editing the capabilities does not seem to change the .entitlements file in consistent ways, so I'm not sure this is a potential part of the problem.

While running the app on a device in Debug, the console shows these suspicious logs:

[assertion] Error acquiring assertion: <Error Domain=RBSServiceErrorDomain Code=1 "(originator doesn't have entitlement com.apple.runningboard.assertions.webkit AND originator doesn't have entitlement com.apple.multitasking.systemappassertions)" UserInfo={NSLocalizedFailureReason=(originator doesn't have entitlement com.apple.runningboard.assertions.webkit AND originator doesn't have entitlement com.apple.multitasking.systemappassertions)}>

[ProcessSuspension] 0x102cbca50 - ProcessAssertion: Failed to acquire RBS assertion 'WebKit Media Playback' for process with PID=476, error: Error Domain=RBSServiceErrorDomain Code=1 "(originator doesn't have entitlement com.apple.runningboard.assertions.webkit AND originator doesn't have entitlement com.apple.multitasking.systemappassertions)" UserInfo={NSLocalizedFailureReason=(originator doesn't have entitlement com.apple.runningboard.assertions.webkit AND originator doesn't have entitlement com.apple.multitasking.systemappassertions)}

The mentioned entitlements com.apple.runningboard.assertions.webkit and com.apple.multitasking.systemappassertions seem to be private / undocumented. I've tried adding them anyways just to see whether that helps, and uninstalled the app to get a fresh install. It didn't work. So I attempted submitting a release build to TestFlight, but App Store Connect rejected the build due to unsupported use of these entitlements.

I also tried keeping the WKWebView alive by repeatedly injecting JavaScript evaluating "1*1" every 0.2 seconds, as some suggested. This didn't help either.

Is there any way to keep WebRTC and the microphone alive while a WKWebView-based app enters the background?

I consider it a blocking bug, as it not being able to background the app while talking to others makes it useless in productivity contexts (which is the app's focus).

If I've missed something, I'd be glad to hear about it.

Thanks

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