Plugin clients: Fix bypass behaviours to match getBypassParameter() documentation

BREAKING-CHANGES.txt

@@ -4,6 +4,36 @@ JUCE breaking changes
 develop
 =======
 
+Change
+------
+Plugin wrappers will no longer call processBlockBypassed() if the wrapped
+AudioProcessor returns a parameter from getBypassParameter().
+
+Possible Issues
+---------------
+Plugins that used to depend on processBlockBypassed() being called may no
+longer correctly enter a bypassed state.
+
+Workaround
+----------
+AudioProcessors that implement getBypassParameter() must check the current
+value of the bypass parameter on each call to processBlock(), and bypass
+processing as appropriate. When switching between bypassed and non-bypassed
+states, the plugin must use some sort of ramping or smoothing to avoid
+discontinuities in the output. If the plugin introduces latency when not
+bypassed, the plugin must delay its output when in bypassed mode so that the
+overall latency does not change when enabling/disabling bypass.
+
+Rationale
+---------
+The documentation for AudioProcessor::getBypassParameter() says
+> if this method returns a non-null value, you should never call
+  processBlockBypassed but use the returned parameter to control the bypass
+  state instead.
+Some plugin wrappers were not following this rule. After this change, the
+behaviour of all plugin wrappers is consistent with the documented behaviour.
+
+
 Change
 ------
 The ComponentPeer::getFrameSize() function has been deprecated on Linux.

modules/juce_audio_plugin_client/AAX/juce_AAX_Wrapper.cpp

@@ -1533,7 +1533,7 @@ namespace AAXClasses
                     }
                 }
 
-                if (bypass)
+                if (bypass && pluginInstance->getBypassParameter() == nullptr)
                     pluginInstance->processBlockBypassed (buffer, midiBuffer);
                 else
                     pluginInstance->processBlock (buffer, midiBuffer);

modules/juce_audio_plugin_client/AU/juce_AUv3_Wrapper.mm

@@ -1652,7 +1652,7 @@ private:
 
         if (processor.isSuspended())
             buffer.clear();
-        else if (bypassParam != nullptr && [au shouldBypassEffect])
+        else if (bypassParam == nullptr && [au shouldBypassEffect])
             processor.processBlockBypassed (buffer, midiBuffer);
         else
             processor.processBlock (buffer, midiBuffer);

modules/juce_audio_plugin_client/RTAS/juce_RTAS_Wrapper.cpp

@@ -588,7 +588,7 @@ public:
 
                 AudioBuffer<float> chans (channels, totalChans, numSamples);
 
-                if (mBypassed)
+                if (mBypassed && juceFilter->getBypassParameter() == nullptr)
                     juceFilter->processBlockBypassed (chans, midiEvents);
                 else
                     juceFilter->processBlock (chans, midiEvents);
@@ -685,6 +685,10 @@ public:
         else
         {
             mBypassed = (value > 0);
+
+            if (auto* param = juceFilter->getBypassParameter())
+                if (mBypassed != (param->getValue() >= 0.5f))
+                    param.setValueNotifyingHost (mBypassed ? 1.0f : 0.0f);
         }
 
         return CProcess::UpdateControlValue (controlIndex, value);

modules/juce_audio_plugin_client/Unity/juce_Unity_Wrapper.cpp

@@ -350,6 +350,11 @@ public:
 
     void process (float* inBuffer, float* outBuffer, int bufferSize, int numInChannels, int numOutChannels, bool isBypassed)
     {
+        // If the plugin has a bypass parameter, set it to the current bypass state
+        if (auto* param = pluginInstance->getBypassParameter())
+            if (isBypassed != (param->getValue() >= 0.5f))
+                param->setValueNotifyingHost (isBypassed ? 1.0f : 0.0f);
+
         for (int pos = 0; pos < bufferSize;)
         {
             auto max = jmin (bufferSize - pos, samplesPerBlock);
@@ -452,7 +457,7 @@ private:
             {
                 MidiBuffer mb;
 
-                if (isBypassed)
+                if (isBypassed && pluginInstance->getBypassParameter() == nullptr)
                     pluginInstance->processBlockBypassed (scratchBuffer, mb);
                 else
                     pluginInstance->processBlock (scratchBuffer, mb);
@@ -619,8 +624,7 @@ namespace UnityCallbacks
             auto isMuted   = ((state->flags & stateIsMuted)   != 0);
             auto isPaused  = ((state->flags & stateIsPaused)  != 0);
 
-            auto bypassed = ! isPlaying || (isMuted || isPaused);
-
+            const auto bypassed = ! isPlaying || (isMuted || isPaused);
             pluginInstance->process (inBuffer, outBuffer, static_cast<int> (bufferSize), numInChannels, numOutChannels, bypassed);
         }
         else

modules/juce_audio_plugin_client/VST/juce_VST_Wrapper.cpp

@@ -447,7 +447,7 @@ public:
                     const int numChannels = jmax (numIn, numOut);
                     AudioBuffer<FloatType> chans (tmpBuffers.channels, isMidiEffect ? 0 : numChannels, numSamples);
 
-                    if (isBypassed)
+                    if (isBypassed && processor->getBypassParameter() == nullptr)
                         processor->processBlockBypassed (chans, midiEvents);
                     else
                         processor->processBlock (chans, midiEvents);
@@ -737,7 +737,7 @@ public:
     void parameterValueChanged (int, float newValue) override
     {
         // this can only come from the bypass parameter
-        isBypassed = (newValue != 0.0f);
+        isBypassed = (newValue >= 0.5f);
     }
 
     void parameterGestureChanged (int, bool) override {}
@@ -1800,10 +1800,10 @@ private:
 
     pointer_sized_int handleSetBypass (VstOpCodeArguments args)
     {
-        isBypassed = (args.value != 0);
+        isBypassed = args.value != 0;
 
-        if (auto* bypass = processor->getBypassParameter())
-            bypass->setValueNotifyingHost (isBypassed ? 1.0f : 0.0f);
+        if (auto* param = processor->getBypassParameter())
+            param->setValueNotifyingHost (isBypassed ? 1.0f : 0.0f);
 
         return 1;
     }

modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp

@@ -2370,10 +2370,10 @@ public:
     tresult PLUGIN_API getRoutingInfo (Vst::RoutingInfo&, Vst::RoutingInfo&) override   { return kNotImplemented; }
 
     //==============================================================================
-    bool isBypassed()
+    bool isBypassed() const
     {
         if (auto* bypassParam = comPluginInstance->getBypassParameter())
-            return (bypassParam->getValue() != 0.0f);
+            return bypassParam->getValue() >= 0.5f;
 
         return false;
     }
@@ -3374,7 +3374,9 @@ private:
                 if (totalInputChans == pluginInstance->getTotalNumInputChannels()
                  && totalOutputChans == pluginInstance->getTotalNumOutputChannels())
                 {
-                    if (isBypassed())
+                    // processBlockBypassed should only ever be called if the AudioProcessor doesn't
+                    // return a valid parameter from getBypassParameter
+                    if (pluginInstance->getBypassParameter() == nullptr && comPluginInstance->getBypassParameter()->getValue() >= 0.5f)
                         pluginInstance->processBlockBypassed (buffer, midiBuffer);
                     else
                         pluginInstance->processBlock (buffer, midiBuffer);
@@ -3489,7 +3491,7 @@ private:
             ptr = {};
         }
 
-        T* operator->()               { return ptr.operator->(); }
+        T* operator->() const         { return ptr.operator->(); }
         T* get() const noexcept       { return ptr.get(); }
         operator T*() const noexcept  { return ptr.get(); }