From 04fdc4c20983c54d3bdaf6355814d29ad827c761 Mon Sep 17 00:00:00 2001
From: ed <eddavies95@gmail.com>
Date: Fri, 9 Apr 2021 16:45:28 +0100
Subject: [PATCH] Standalone:  Add a dummy output channel to MIDI effect
 plug-ins

---
 .../Standalone/juce_StandaloneFilterWindow.h  | 41 ++++++++++++-------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/modules/juce_audio_plugin_client/Standalone/juce_StandaloneFilterWindow.h b/modules/juce_audio_plugin_client/Standalone/juce_StandaloneFilterWindow.h
index 7ef90c643b..4ee4c3e55b 100644
--- a/modules/juce_audio_plugin_client/Standalone/juce_StandaloneFilterWindow.h
+++ b/modules/juce_audio_plugin_client/Standalone/juce_StandaloneFilterWindow.h
@@ -128,13 +128,7 @@ public:
         processor->disableNonMainBuses();
         processor->setRateAndBufferSizeDetails (44100, 512);
 
-        int inChannels = (channelConfiguration.size() > 0 ? channelConfiguration[0].numIns
-                                                          : processor->getMainBusNumInputChannels());
-
-        int outChannels = (channelConfiguration.size() > 0 ? channelConfiguration[0].numOuts
-                                                           : processor->getMainBusNumOutputChannels());
-
-        processorHasPotentialFeedbackLoop = (inChannels > 0 && outChannels > 0);
+        processorHasPotentialFeedbackLoop = (getNumInputChannels() > 0 && getNumOutputChannels() > 0);
     }
 
     virtual void deletePlugin()
@@ -143,6 +137,24 @@ public:
         processor = nullptr;
     }
 
+    int getNumInputChannels() const
+    {
+        if (processor == nullptr)
+            return 0;
+
+        return (channelConfiguration.size() > 0 ? channelConfiguration[0].numIns
+                                                : processor->getMainBusNumInputChannels());
+    }
+
+    int getNumOutputChannels() const
+    {
+        if (processor == nullptr)
+            return 0;
+
+        return (channelConfiguration.size() > 0 ? channelConfiguration[0].numOuts
+                                                : processor->getMainBusNumOutputChannels());
+    }
+
     static String getFilePatterns (const String& fileSuffix)
     {
         if (fileSuffix.isEmpty())
@@ -305,18 +317,17 @@ public:
            #endif
         }
 
-        auto totalInChannels  = processor->getMainBusNumInputChannels();
-        auto totalOutChannels = processor->getMainBusNumOutputChannels();
+        auto inputChannels  = getNumInputChannels();
+        auto outputChannels = getNumOutputChannels();
 
-        if (channelConfiguration.size() > 0)
+        if (inputChannels == 0 && outputChannels == 0 && processor->isMidiEffect())
         {
-            auto defaultConfig = channelConfiguration.getReference (0);
-            totalInChannels  = defaultConfig.numIns;
-            totalOutChannels = defaultConfig.numOuts;
+            // add a dummy output channel for MIDI effect plug-ins so they can receive audio callbacks
+            outputChannels = 1;
         }
 
-        deviceManager.initialise (enableAudioInput ? totalInChannels : 0,
-                                  totalOutChannels,
+        deviceManager.initialise (enableAudioInput ? inputChannels : 0,
+                                  outputChannels,
                                   savedState.get(),
                                   true,
                                   preferredDefaultDeviceName,