Fixed occasional COMException in GetSpotifyVolumeObject (#222)

* Added volume controls in Example app

* Fixed occasional COMException when using Get- or SetSpotifyVolume

This exception only happens if Spotify is using an audio device different from the default one. Such a thing is only possible (as of v1.0.75.483.g7ff4a0dc) when using the "--enable-audio-graph" command line argument, that makes available the "Playback device" advanced option in Spotify.

Author: aleab

SpotifyAPI.Example/LocalControl.Designer.cs

@@ -72,6 +72,8 @@ public void UpdateInfos()
 
             if (status.Track != null) //Update track infos
                 UpdateTrack(status.Track);
+
+            RefreshVolumeMixerVolume();
         }
 
         public async void UpdateTrack(Track track)
@@ -106,6 +108,11 @@ public void UpdatePlayingStatus(bool playing)
             isPlayingLabel.Text = playing.ToString();
         }
 
+        public void RefreshVolumeMixerVolume()
+        {
+            volumeMixerLabel.Text = _spotify.GetSpotifyVolume().ToString(CultureInfo.InvariantCulture);
+        }
+
         private void _spotify_OnVolumeChange(object sender, VolumeChangeEventArgs e)
         {
             if (InvokeRequired)
@@ -178,6 +185,24 @@ private void skipBtn_Click(object sender, EventArgs e)
             _spotify.Skip();
         }
 
+        private void volumeUpBtn_Click(object sender, EventArgs e)
+        {
+            float currentVolume = _spotify.GetSpotifyVolume();
+            float newVolume = currentVolume + 2.0f;
+            _spotify.SetSpotifyVolume(newVolume >= 100.0f ? 100.0f : newVolume);
+
+            RefreshVolumeMixerVolume();
+        }
+
+        private void volumeDownBtn_Click(object sender, EventArgs e)
+        {
+            float currentVolume = _spotify.GetSpotifyVolume();
+            float newVolume = currentVolume - 2.0f;
+            _spotify.SetSpotifyVolume(newVolume <= 0.0f ? 0.0f : newVolume);
+
+            RefreshVolumeMixerVolume();
+        }
+
         private static String FormatTime(double sec)
         {
             TimeSpan span = TimeSpan.FromSeconds(sec);

SpotifyAPI.Example/LocalControl.cs

@@ -67,11 +67,13 @@ internal static void MuteSpotify(bool mute)
             Marshal.ReleaseComObject(volume);
         }
 
-        private static ISimpleAudioVolume GetSpotifyVolumeObject() {
-            return (from p in Process.GetProcessesByName(SpotifyProcessName)
-                    let vol = GetVolumeObject(p.Id)
-                    where vol != null
-                    select vol).FirstOrDefault();
+        private static ISimpleAudioVolume GetSpotifyVolumeObject()
+        {
+            var audioVolumeObjects = from p in Process.GetProcessesByName(SpotifyProcessName)
+                                     let vol = GetVolumeObject(p.Id)
+                                     where vol != null
+                                     select vol;
+            return audioVolumeObjects.FirstOrDefault();
         }
 
         private static ISimpleAudioVolume GetVolumeObject(int pid)
@@ -81,10 +83,59 @@ private static ISimpleAudioVolume GetVolumeObject(int pid)
             IMmDevice speakers;
             deviceEnumerator.GetDefaultAudioEndpoint(EDataFlow.ERender, ERole.EMultimedia, out speakers);
 
+            string defaultDeviceId;
+            speakers.GetId(out defaultDeviceId);
+
+            ISimpleAudioVolume volumeControl = GetVolumeObject(pid, speakers);
+            Marshal.ReleaseComObject(speakers);
+
+            if (volumeControl == null)
+            {
+                // If volumeControl is null, then the process's volume object might be on a different device.
+                // This happens if the process doesn't use the default device.
+                // 
+                // As far as Spotify is concerned, if using the "--enable-audio-graph" command line argument,
+                // a new option becomes available in the Settings that makes it possible to change the playback device.
+
+                IMmDeviceCollection deviceCollection;
+                deviceEnumerator.EnumAudioEndpoints(EDataFlow.ERender, EDeviceState.Active, out deviceCollection);
+
+                int count;
+                deviceCollection.GetCount(out count);
+                for (int i = 0; i < count; i++)
+                {
+                    IMmDevice device;
+                    deviceCollection.Item(i, out device);
+
+                    string deviceId;
+                    device.GetId(out deviceId);
+
+                    try
+                    {
+                        if (deviceId == defaultDeviceId)
+                            continue;
+
+                        volumeControl = GetVolumeObject(pid, device);
+                        if (volumeControl != null)
+                            break;
+                    }
+                    finally
+                    {
+                        Marshal.ReleaseComObject(device);
+                    }
+                }
+            }
+            
+            Marshal.ReleaseComObject(deviceEnumerator);
+            return volumeControl;
+        }
+
+        private static ISimpleAudioVolume GetVolumeObject(int pid, IMmDevice device)
+        {
             // activate the session manager. we need the enumerator
             Guid iidIAudioSessionManager2 = typeof(IAudioSessionManager2).GUID;
             object o;
-            speakers.Activate(ref iidIAudioSessionManager2, 0, IntPtr.Zero, out o);
+            device.Activate(ref iidIAudioSessionManager2, 0, IntPtr.Zero, out o);
             IAudioSessionManager2 mgr = (IAudioSessionManager2)o;
 
             // enumerate sessions for on this device
@@ -105,23 +156,20 @@ private static ISimpleAudioVolume GetVolumeObject(int pid)
 
                 if (cpid == pid)
                 {
-                    volumeControl = (ISimpleAudioVolume) ctl;
+                    volumeControl = (ISimpleAudioVolume)ctl;
                     break;
                 }
                 Marshal.ReleaseComObject(ctl);
             }
             Marshal.ReleaseComObject(sessionEnumerator);
             Marshal.ReleaseComObject(mgr);
-            Marshal.ReleaseComObject(speakers);
-            Marshal.ReleaseComObject(deviceEnumerator);
             return volumeControl;
         }
 
         [ComImport]
         [Guid("BCDE0395-E52F-467C-8E3D-C4579291692E")]
         private class MMDeviceEnumerator
         {
-
         }
 
         private enum EDataFlow
@@ -140,10 +188,21 @@ private enum ERole
             ERoleEnumCount
         }
 
+        [Flags]
+        private enum EDeviceState
+        {
+            Active = 0x00000001,
+            Disabled = 0x00000002,
+            NotPresent = 0x00000004,
+            UnPlugged = 0x00000008,
+            All = 0x0000000F
+        }
+
         [Guid("A95664D2-9614-4F35-A746-DE8DB63617E6"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
         private interface IMmDeviceEnumerator
         {
-            int NotImpl1();
+            [PreserveSig]
+            int EnumAudioEndpoints(EDataFlow dataFlow, EDeviceState stateMask, [Out] out IMmDeviceCollection deviceCollection);
 
             [PreserveSig]
             int GetDefaultAudioEndpoint(EDataFlow dataFlow, ERole role, out IMmDevice ppDevice);
@@ -154,6 +213,21 @@ private interface IMmDevice
         {
             [PreserveSig]
             int Activate(ref Guid iid, int dwClsCtx, IntPtr pActivationParams, [MarshalAs(UnmanagedType.IUnknown)] out object ppInterface);
+
+            int OpenPropertyStore_NotImpl();
+
+            [PreserveSig]
+            int GetId([Out, MarshalAs(UnmanagedType.LPWStr)] out string ppstrId);
+        }
+
+        [Guid("0BD7A1BE-7A1A-44DB-8397-CC5392387B5E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
+        private interface IMmDeviceCollection
+        {
+            [PreserveSig]
+            int GetCount(out int deviceCount);
+
+            [PreserveSig]
+            int Item(int deviceIndex, [Out] out IMmDevice device);
         }
 
         [Guid("77AA99A0-1BD6-484F-8BC7-2C654C9A9B6F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]