Patch to add MIDI output support to keijiro's MidiInput for Unity (https://github.com/keijiro/unity-midi-input)

unity-midi-input-ouput.diff

--- a/UnityMidiReceiver/UnityMidiReceiver.cpp
+++ b/UnityMidiReceiver/UnityMidiReceiver.cpp
@@ -37,6 +37,7 @@ namespace
 
     // MIDI device handle vector.
 	std::vector<HMIDIIN> handles;
+	std::vector<HMIDIOUT> outDeviceHandles;
 
     // Incoming MIDI message queue.
     std::queue<Message> messageQueue;
@@ -86,6 +87,18 @@ namespace
 
             handles.push_back(handle);
         }
+
+		auto outDeviceCount = midiOutGetNumDevs();
+		for (auto i = 0U; i < outDeviceCount; i++)
+		{
+			HMIDIOUT handle;
+			DWORD_PTR callback = reinterpret_cast<DWORD_PTR>(MyMidiInProc);
+			// DWORD_PTR instance = reinterpret_cast<DWORD_PTR>(&messageDelegate);
+			MMRESULT result = midiOutOpen(&handle, i, callback, NULL, CALLBACK_FUNCTION);
+			assert(result == MMSYSERR_NOERROR);
+
+			outDeviceHandles.push_back(handle);
+		}
     }
 }
 
@@ -146,3 +159,24 @@ extern "C" uint64_t EXPORT_API UnityMIDIReceiver_DequeueIncomingData()
 
     return m.uint64Value;
 }
+
+// BOOKMARK
+extern "C" void EXPORT_API UnityMIDIReceiver_Send(uint8_t aStatus, uint8_t aData1, uint8_t aData2)
+{
+	std::string errorString;
+	MMRESULT result;
+
+	// Pack MIDI bytes into double word.
+	DWORD packet;
+	unsigned char *ptr = (unsigned char *)&packet;
+	ptr[0] = aStatus;
+	ptr[1] = aData1;
+	ptr[2] = aData2;
+
+	// Send the message immediately.
+	for (auto& handle : outDeviceHandles)
+	{
+		result = midiOutShortMsg(handle, packet);
+		assert(result == MMSYSERR_NOERROR);
+	}
+}

--- a/Assets/Scripts/MidiInput.cs
+++ b/Assets/Scripts/MidiInput.cs
@@ -70,6 +70,15 @@ public class MidiInput : MonoBehaviour
             return 0.0f;
         }
     }
+
+    public static void SetCC(int channel, int value) {
+        uint status = 0xb0;
+        Send(status, (uint) channel, (uint) value);
+    }
+
+    public static void Send (uint status, uint data1, uint data2) {
+        _Send(status, data1, data2);
+    }
     #endregion
 
     #region MIDI message sturcture
@@ -245,6 +254,9 @@ public class MidiInput : MonoBehaviour
     [DllImport ("UnityMIDIReceiver", EntryPoint="UnityMIDIReceiver_DequeueIncomingData")]
     public static extern ulong DequeueIncomingData ();
 
+    [DllImport ("UnityMIDIReceiver", EntryPoint="UnityMIDIReceiver_Send")]
+    public static extern void _Send (uint status, uint data1, uint data2);
+
     [DllImport ("UnityMIDIReceiver")]
     private static extern System.IntPtr UnityMIDIReceiver_GetEndpointName (uint id);