Navigation support for upcoming Element Call Picture in Picture mode. (#3174)

ElementX/Sources/Screens/CallScreen/CallScreenViewModel.swift

@@ -14,6 +14,7 @@
 // limitations under the License.
 //
 
+import AVKit
 import CallKit
 import Combine
 import SwiftUI
@@ -23,6 +24,7 @@ typealias CallScreenViewModelType = StateStoreViewModel<CallScreenViewState, Cal
 class CallScreenViewModel: CallScreenViewModelType, CallScreenViewModelProtocol {
     private let elementCallService: ElementCallServiceProtocol
     private let roomProxy: RoomProxyProtocol
+    private let isPictureInPictureEnabled: Bool
     
     private let widgetDriver: ElementCallWidgetDriverProtocol
     
@@ -45,12 +47,14 @@ class CallScreenViewModel: CallScreenViewModelType, CallScreenViewModelProtocol
          clientID: String,
          elementCallBaseURL: URL,
          elementCallBaseURLOverride: URL?,
+         elementCallPictureInPictureEnabled: Bool,
          colorScheme: ColorScheme,
          appHooks: AppHooks) {
         guard let deviceID = clientProxy.deviceID else { fatalError("Missing device ID for the call.") }
         
         self.elementCallService = elementCallService
         self.roomProxy = roomProxy
+        isPictureInPictureEnabled = elementCallPictureInPictureEnabled
         
         widgetDriver = roomProxy.elementCallWidgetDriver(deviceID: deviceID)
         
@@ -151,6 +155,23 @@ class CallScreenViewModel: CallScreenViewModelType, CallScreenViewModelProtocol
                     syncUpdateCancellable = nil
                 }
             }, receiveValue: { _ in })
+        
+        // Use did start otherwise there's a black box left on the screen during the pip controller animation.
+        NotificationCenter.default.publisher(for: .init("AVPictureInPictureControllerDidStartNotification"))
+            .sink { [weak self] notification in
+                guard let self else { return }
+                let controller = notification.object as? AVPictureInPictureController
+                actionsSubject.send(.pictureInPictureStarted(controller))
+            }
+            .store(in: &cancellables)
+        
+        NotificationCenter.default.publisher(for: .init("AVPictureInPictureControllerWillStopNotification"))
+            .sink { [weak self] _ in
+                guard let self else { return }
+                actionsSubject.send(.pictureInPictureStopped)
+                Task { try await self.state.bindings.javaScriptEvaluator?("controls.disableCompatPip()") }
+            }
+            .store(in: &cancellables)
     }
     
     override func process(viewAction: CallScreenViewAction) {
@@ -158,6 +179,8 @@ class CallScreenViewModel: CallScreenViewModelType, CallScreenViewModelProtocol
         case .urlChanged(let url):
             guard let url else { return }
             MXLog.info("URL changed to: \(url)")
+        case .navigateBack:
+            handleBackwardsNavigation()
         }
     }
     
@@ -171,6 +194,29 @@ class CallScreenViewModel: CallScreenViewModelType, CallScreenViewModelProtocol
     
     // MARK: - Private
     
+    private func handleBackwardsNavigation() {
+        #if targetEnvironment(simulator)
+        if UIDevice.current.isPhone {
+            MXLog.warning("The iPhone simulator doesn't support PiP.")
+            actionsSubject.send(.dismiss)
+            return
+        }
+        #endif
+        
+        guard isPictureInPictureEnabled, state.url != nil else {
+            actionsSubject.send(.dismiss)
+            return
+        }
+        
+        Task {
+            try await state.bindings.javaScriptEvaluator?("controls.enableCompatPip()")
+            // Enable this check when implemented on web.
+            // if result as? Bool != true {
+            //    actionsSubject.send(.dismiss)
+            // }
+        }
+    }
+    
     private func setAudioEnabled(_ enabled: Bool) async {
         let message = ElementCallWidgetMessage(direction: .toWidget,
                                                action: .mediaState,