Bring managed iOS client to feature parity

clients/apple/dotnet/VoiceCat.iOS/BroadcastAudioPump.cs

@@ -12,8 +12,12 @@ internal sealed class BroadcastAudioPump : IAsyncDisposable
     private Task worker = Task.CompletedTask;
     private VoiceCatClient? client;
     private uint streamId;
+    private bool active;
     private readonly short[] scratch = new short[Frame * 2];
 
+    internal event Action? Changed;
+    internal bool IsActive => active;
+
     internal void Start(VoiceCatClient owner) { client = owner; worker = RunAsync(stop.Token); }
 
     private async Task RunAsync(CancellationToken token)
@@ -35,12 +39,12 @@ internal sealed class BroadcastAudioPump : IAsyncDisposable
         using MemoryMappedViewAccessor view = map.CreateViewAccessor(0, Header + Capacity * sizeof(short), MemoryMappedFileAccess.ReadWrite);
         if (view.ReadUInt32(0) != Magic || view.ReadUInt32(4) != Version) throw new InvalidDataException("Unsupported broadcast ring.");
         bool active = view.ReadUInt32(16) != 0;
-        if (!active) { StopStream(); return; }
+        if (!active) { StopStream(); SetActive(false); return; }
         VoiceCatClient owner = client ?? throw new IOException("Client disconnected.");
         if (streamId == 0)
         {
             StreamInfo stream = await owner.StartStreamAsync(StreamKind.StreamScreenAudio, "Screen audio", 2, token).ConfigureAwait(false);
-            streamId = stream.StreamId; view.Write(32, view.ReadUInt64(24));
+            streamId = stream.StreamId; view.Write(32, view.ReadUInt64(24)); SetActive(true);
         }
         ulong write = view.ReadUInt64(24), read = view.ReadUInt64(32);
         if (write - read > Capacity) read = write - Capacity;
@@ -63,8 +67,10 @@ internal sealed class BroadcastAudioPump : IAsyncDisposable
         try { client.StopStream(id); } catch (Exception exception) when (exception is IOException or InvalidOperationException) { }
     }
 
+    private void SetActive(bool value) { if (active == value) return; active = value; Changed?.Invoke(); }
+
     public async ValueTask DisposeAsync()
     {
-        stop.Cancel(); try { await worker.ConfigureAwait(false); } catch (OperationCanceledException) { } StopStream(); stop.Dispose();
+        stop.Cancel(); try { await worker.ConfigureAwait(false); } catch (OperationCanceledException) { } StopStream(); SetActive(false); stop.Dispose();
     }
 }