Added an AudioProcessorPlayer::setMidiOutput() method for forwarding MIDI messages from the AudioProcessor and updated the standalone plugin holder to use this

modules/juce_audio_plugin_client/Standalone/juce_StandaloneFilterWindow.h

@@ -118,7 +118,6 @@ public:
     //==============================================================================
     virtual void createPlugin()
     {
-
       #if JUCE_MODULE_AVAILABLE_juce_audio_plugin_client
         processor.reset (::createPluginFilterOfType (AudioProcessor::wrapperType_Standalone));
       #else
@@ -427,7 +426,8 @@ private:
               deviceSelector (deviceManagerToUse,
                               minAudioInputChannels, maxAudioInputChannels,
                               minAudioOutputChannels, maxAudioOutputChannels,
-                              true, false,
+                              true,
+                              (pluginHolder.processor.get() != nullptr && pluginHolder.processor->producesMidi()),
                               true, false),
               shouldMuteLabel  ("Feedback Loop:", "Feedback Loop:"),
               shouldMuteButton ("Mute audio input")
@@ -508,10 +508,12 @@ private:
         emptyBuffer.clear();
 
         player.audioDeviceAboutToStart (device);
+        player.setMidiOutput (deviceManager.getDefaultMidiOutput());
     }
 
     void audioDeviceStopped() override
     {
+        player.setMidiOutput (nullptr);
         player.audioDeviceStopped();
         emptyBuffer.setSize (0, 0);
     }

modules/juce_audio_utils/players/juce_AudioProcessorPlayer.cpp

@@ -88,6 +88,15 @@ void AudioProcessorPlayer::setDoublePrecisionProcessing (bool doublePrecision)
     }
 }
 
+void AudioProcessorPlayer::setMidiOutput (MidiOutput* midiOutputToUse)
+{
+    if (midiOutput != midiOutputToUse)
+    {
+        const ScopedLock sl (lock);
+        midiOutput = midiOutputToUse;
+    }
+}
+
 //==============================================================================
 void AudioProcessorPlayer::audioDeviceIOCallback (const float** const inputChannelData,
                                                   const int numInputChannels,
@@ -163,6 +172,9 @@ void AudioProcessorPlayer::audioDeviceIOCallback (const float** const inputChann
                     processor->processBlock (buffer, incomingMidi);
                 }
 
+                if (midiOutput != nullptr)
+                    midiOutput->sendBlockOfMessagesNow (incomingMidi);
+
                 return;
             }
         }

modules/juce_audio_utils/players/juce_AudioProcessorPlayer.h

@@ -35,7 +35,8 @@ namespace juce
     give it a processor to use by calling setProcessor().
 
     It's also a MidiInputCallback, so you can connect it to both an audio and midi
-    input to send both streams through the processor.
+    input to send both streams through the processor. To set a MidiOutput for the processor,
+    use the setMidiOutput() method.
 
     @see AudioProcessor, AudioProcessorGraph
 
@@ -68,18 +69,26 @@ public:
     */
     MidiMessageCollector& getMidiMessageCollector() noexcept        { return messageCollector; }
 
+    /** Sets the MIDI output that should be used, if required.
+
+        The MIDI output will not be deleted or owned by this object. If the MIDI output is
+        deleted, pass a nullptr to this method.
+    */
+    void setMidiOutput (MidiOutput* midiOutputToUse);
+
     /** Switch between double and single floating point precisions processing.
-        The audio IO callbacks will still operate in single floating point
-        precision, however, all internal processing including the
-        AudioProcessor will be processed in double floating point precision if
-        the AudioProcessor supports it (see
-        AudioProcessor::supportsDoublePrecisionProcessing()).
-        Otherwise, the processing will remain single precision irrespective of
-        the parameter doublePrecision. */
+
+        The audio IO callbacks will still operate in single floating point precision,
+        however, all internal processing including the AudioProcessor will be processed in
+        double floating point precision if the AudioProcessor supports it (see
+        AudioProcessor::supportsDoublePrecisionProcessing()). Otherwise, the processing will
+        remain single precision irrespective of the parameter doublePrecision.
+    */
     void setDoublePrecisionProcessing (bool doublePrecision);
 
     /** Returns true if this player processes internally processes the samples with
-        double floating point precision. */
+        double floating point precision.
+    */
     inline bool getDoublePrecisionProcessing() { return isDoublePrecision; }
 
     //==============================================================================
@@ -107,6 +116,7 @@ private:
 
     MidiBuffer incomingMidi;
     MidiMessageCollector messageCollector;
+    MidiOutput* midiOutput = nullptr;
 
     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AudioProcessorPlayer)
 };