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.

SpotifyAPI.Example/LocalControl.Designer.cs

@@ -61,6 +61,10 @@
             this.artistLinkLabel = new System.Windows.Forms.LinkLabel();
             this.titleLinkLabel = new System.Windows.Forms.LinkLabel();
             this.smallAlbumPicture = new System.Windows.Forms.PictureBox();
+            this.volumeDownBtn = new System.Windows.Forms.Button();
+            this.volumeUpBtn = new System.Windows.Forms.Button();
+            this.label9 = new System.Windows.Forms.Label();
+            this.volumeMixerLabel = new System.Windows.Forms.Label();
             ((System.ComponentModel.ISupportInitialize)(this.bigAlbumPicture)).BeginInit();
             this.groupBox1.SuspendLayout();
             this.trackInfoBox.SuspendLayout();
@@ -69,7 +73,7 @@
             // 
             // bigAlbumPicture
             // 
-            this.bigAlbumPicture.Location = new System.Drawing.Point(327, 13);
+            this.bigAlbumPicture.Location = new System.Drawing.Point(330, 13);
             this.bigAlbumPicture.Name = "bigAlbumPicture";
             this.bigAlbumPicture.Size = new System.Drawing.Size(640, 640);
             this.bigAlbumPicture.TabIndex = 2;
@@ -77,6 +81,10 @@
             // 
             // groupBox1
             // 
+            this.groupBox1.Controls.Add(this.volumeMixerLabel);
+            this.groupBox1.Controls.Add(this.label9);
+            this.groupBox1.Controls.Add(this.volumeUpBtn);
+            this.groupBox1.Controls.Add(this.volumeDownBtn);
             this.groupBox1.Controls.Add(this.repeatShuffleLabel);
             this.groupBox1.Controls.Add(this.label6);
             this.groupBox1.Controls.Add(this.versionLabel);
@@ -428,6 +436,50 @@
             this.smallAlbumPicture.TabIndex = 5;
             this.smallAlbumPicture.TabStop = false;
             // 
+            // volumeDownBtn
+            // 
+            this.volumeDownBtn.Font = new System.Drawing.Font("Microsoft Sans Serif", 8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
+            this.volumeDownBtn.Location = new System.Drawing.Point(247, 134);
+            this.volumeDownBtn.Margin = new System.Windows.Forms.Padding(0);
+            this.volumeDownBtn.Name = "volumeDownBtn";
+            this.volumeDownBtn.Size = new System.Drawing.Size(65, 24);
+            this.volumeDownBtn.TabIndex = 32;
+            this.volumeDownBtn.Text = "Volume-";
+            this.volumeDownBtn.UseVisualStyleBackColor = true;
+            this.volumeDownBtn.Click += new System.EventHandler(this.volumeDownBtn_Click);
+            // 
+            // volumeUpBtn
+            // 
+            this.volumeUpBtn.Font = new System.Drawing.Font("Microsoft Sans Serif", 8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
+            this.volumeUpBtn.Location = new System.Drawing.Point(247, 110);
+            this.volumeUpBtn.Margin = new System.Windows.Forms.Padding(0);
+            this.volumeUpBtn.Name = "volumeUpBtn";
+            this.volumeUpBtn.Size = new System.Drawing.Size(65, 24);
+            this.volumeUpBtn.TabIndex = 33;
+            this.volumeUpBtn.Text = "Volume+";
+            this.volumeUpBtn.UseVisualStyleBackColor = true;
+            this.volumeUpBtn.Click += new System.EventHandler(this.volumeUpBtn_Click);
+            // 
+            // label9
+            // 
+            this.label9.AutoSize = true;
+            this.label9.Font = new System.Drawing.Font("Microsoft Sans Serif", 10F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
+            this.label9.Location = new System.Drawing.Point(7, 117);
+            this.label9.Name = "label9";
+            this.label9.Size = new System.Drawing.Size(155, 17);
+            this.label9.TabIndex = 34;
+            this.label9.Text = "Volume Mixer\'s volume:";
+            // 
+            // volumeMixerLabel
+            // 
+            this.volumeMixerLabel.AutoSize = true;
+            this.volumeMixerLabel.Font = new System.Drawing.Font("Microsoft Sans Serif", 10F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
+            this.volumeMixerLabel.Location = new System.Drawing.Point(168, 117);
+            this.volumeMixerLabel.Name = "volumeMixerLabel";
+            this.volumeMixerLabel.Size = new System.Drawing.Size(13, 17);
+            this.volumeMixerLabel.TabIndex = 35;
+            this.volumeMixerLabel.Text = "-";
+            // 
             // LocalControl
             // 
             this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
@@ -483,5 +535,9 @@
         private System.Windows.Forms.Label label6;
         private System.Windows.Forms.Label repeatShuffleLabel;
         private System.Windows.Forms.Label advertLabel;
+        private System.Windows.Forms.Button volumeUpBtn;
+        private System.Windows.Forms.Button volumeDownBtn;
+        private System.Windows.Forms.Label volumeMixerLabel;
+        private System.Windows.Forms.Label label9;
     }
 }

SpotifyAPI.Example/LocalControl.cs

@@ -72,6 +72,8 @@ namespace SpotifyAPI.Example
 
             if (status.Track != null) //Update track infos
                 UpdateTrack(status.Track);
+
+            RefreshVolumeMixerVolume();
         }
 
         public async void UpdateTrack(Track track)
@@ -106,6 +108,11 @@ namespace SpotifyAPI.Example
             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 @@ namespace SpotifyAPI.Example
             _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/Local/VolumeMixerControl.cs

@@ -67,11 +67,13 @@ namespace SpotifyAPI.Local
             Marshal.ReleaseComObject(volume);
         }
 
-        private static ISimpleAudioVolume GetSpotifyVolumeObject() {
+        private static ISimpleAudioVolume GetSpotifyVolumeObject()
-            return (from p in Process.GetProcessesByName(SpotifyProcessName)
+        {
+            var audioVolumeObjects = from p in Process.GetProcessesByName(SpotifyProcessName)
                                      let vol = GetVolumeObject(p.Id)
                                      where vol != null
-                    select vol).FirstOrDefault();
+                                     select vol;
+            return audioVolumeObjects.FirstOrDefault();
         }
 
         private static ISimpleAudioVolume GetVolumeObject(int pid)
@@ -81,10 +83,59 @@ namespace SpotifyAPI.Local
             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
@@ -112,8 +163,6 @@ namespace SpotifyAPI.Local
             }
             Marshal.ReleaseComObject(sessionEnumerator);
             Marshal.ReleaseComObject(mgr);
-            Marshal.ReleaseComObject(speakers);
-            Marshal.ReleaseComObject(deviceEnumerator);
             return volumeControl;
         }
 
@@ -121,7 +170,6 @@ namespace SpotifyAPI.Local
         [Guid("BCDE0395-E52F-467C-8E3D-C4579291692E")]
         private class MMDeviceEnumerator
         {
-
         }
 
         private enum EDataFlow
@@ -140,10 +188,21 @@ namespace SpotifyAPI.Local
             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 @@ namespace SpotifyAPI.Local
         {
             [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)]