Handle macOS stream errors (#776)

Resolves #331 

Handles stream errors in a way similar to iOS broadcast (by unpublishing
the track so it won't get stuck).

Author: pblazej

.changes/turn-off-display

@@ -0,0 +1 @@
+patch type="fixed" "Screen sharing getting stuck on macOS when the display is turned off"

Sources/LiveKit/Track/Capturers/MacOSScreenCapturer.swift

@@ -101,7 +101,7 @@ public class MacOSScreenCapturer: VideoCapturer, @unchecked Sendable {
         }
 
         // Why does SCStream hold strong reference to delegate?
-        let stream = SCStream(filter: filter, configuration: configuration, delegate: nil)
+        let stream = SCStream(filter: filter, configuration: configuration, delegate: self)
         try stream.addStreamOutput(self, type: .screen, sampleHandlerQueue: nil)
         if #available(macOS 13.0, *) {
             try stream.addStreamOutput(self, type: .audio, sampleHandlerQueue: nil)
@@ -200,6 +200,18 @@ extension MacOSScreenCapturer {
     }
 }
 
+// MARK: - SCStreamDelegate
+
+@available(macOS 12.3, *)
+extension MacOSScreenCapturer: SCStreamDelegate {
+    public func stream(_: SCStream, didStopWithError error: Error) {
+        log("Stream stopped with error: \(error)", .error)
+        Task {
+            try await stopCapture()
+        }
+    }
+}
+
 // MARK: - SCStreamOutput
 
 @available(macOS 12.3, *)

Sources/LiveKit/TrackPublications/LocalTrackPublication.swift

@@ -119,6 +119,17 @@ extension LocalTrackPublication: VideoCapturerDelegate {
                 try await participant.unpublish(publication: self)
             }
         }
+        // A similar check for macOS may be triggered e.g. when the display is powered off.
+        #elseif os(macOS)
+        if #available(macOS 12.3, *), state == .stopped, capturer is MacOSScreenCapturer {
+            Task {
+                guard let participant = try await self.requireParticipant() as? LocalParticipant else {
+                    return
+                }
+
+                try await participant.unpublish(publication: self)
+            }
+        }
         #endif
     }
 }