From 2d9231111699b6ead3df922b07a95eec9db4c114 Mon Sep 17 00:00:00 2001
From: Tom Poole <thomas.poole@roli.com>
Date: Fri, 15 Dec 2017 11:31:45 +0000
Subject: [PATCH] VST3:  Fixed an issue with parallel streams of parameter
 updates during playback

---
 .../VST3/juce_VST3_Wrapper.cpp                     | 14 ++++++++++++--
 .../processors/juce_AudioProcessor.h               |  6 ++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp b/modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp
index d0b65671e1..c2f4869626 100644
--- a/modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp
+++ b/modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp
@@ -241,7 +241,12 @@ public:
             if (v != valueNormalized)
             {
                 valueNormalized = v;
-                owner.setParameter (paramIndex, static_cast<float> (v));
+
+                // Only update the AudioProcessor here if we're not playing,
+                // otherwise we get parallel streams of parameter value updates
+                // during playback
+                if (owner.vst3IsPlaying.get() == 0)
+                    owner.setParameter (paramIndex, static_cast<float> (v));
 
                 changed();
                 return true;
@@ -636,7 +641,6 @@ private:
    #endif
     Vst::ParamID bypassParamID;
 
-
     //==============================================================================
     void setupParameters()
     {
@@ -2031,9 +2035,15 @@ public:
             return kResultFalse;
 
         if (data.processContext != nullptr)
+        {
             processContext = *data.processContext;
+            pluginInstance->vst3IsPlaying = processContext.state & Vst::ProcessContext::kPlaying;
+        }
         else
+        {
             zerostruct (processContext);
+            pluginInstance->vst3IsPlaying = 0;
+        }
 
         midiBuffer.clear();
 
diff --git a/modules/juce_audio_processors/processors/juce_AudioProcessor.h b/modules/juce_audio_processors/processors/juce_AudioProcessor.h
index e58ac7f97d..46f23eae72 100644
--- a/modules/juce_audio_processors/processors/juce_AudioProcessor.h
+++ b/modules/juce_audio_processors/processors/juce_AudioProcessor.h
@@ -1606,6 +1606,12 @@ private:
     template <typename floatType>
     void processBypassed (AudioBuffer<floatType>&, MidiBuffer&);
 
+   #if JucePlugin_Build_VST3
+    friend class JuceVST3EditController;
+    friend class JuceVST3Component;
+    Atomic<int> vst3IsPlaying { 0 };
+   #endif
+
     // This method is no longer used - you can delete it from your AudioProcessor classes.
     JUCE_DEPRECATED_WITH_BODY (virtual bool silenceInProducesSilenceOut() const, { return false; })