AudioProcessorParameter: Break dependency cycle with AudioProcessor

modules/juce_audio_processors/format_types/juce_LegacyAudioParameter.cpp

@@ -40,10 +40,12 @@ JUCE_BEGIN_IGNORE_DEPRECATION_WARNINGS
 class LegacyAudioParameter final : public HostedAudioProcessorParameter
 {
 public:
-    LegacyAudioParameter (AudioProcessor& audioProcessorToUse, int audioParameterIndex)
+    LegacyAudioParameter (AudioProcessorParameter::Listener& listener,
+                          AudioProcessor& audioProcessorToUse,
+                          int audioParameterIndex)
+        : processor (&audioProcessorToUse)
     {
-        processor = &audioProcessorToUse;
+        setOwner (&listener);
-
         setParameterIndex (audioParameterIndex);
         jassert (getParameterIndex() < processor->getNumParameters());
     }
@@ -118,6 +120,9 @@ public:
 
         return {};
     }
+
+private:
+    AudioProcessor* processor = nullptr;
 };
 
 //==============================================================================
@@ -135,6 +140,7 @@ public:
     {
         clear();
 
+        forwarder = AudioProcessor::ParameterChangeForwarder { &audioProcessor };
         legacyParamIDs = forceLegacyParamIDs;
 
         auto numParameters = audioProcessor.getNumParameters();
@@ -147,7 +153,7 @@ public:
                 if (usingManagedParameters)
                     return audioProcessor.getParameters()[i];
 
-                auto newParam = std::make_unique<LegacyAudioParameter> (audioProcessor, i);
+                auto newParam = std::make_unique<LegacyAudioParameter> (forwarder, audioProcessor, i);
                 auto* result = newParam.get();
                 ownedGroup.addChild (std::move (newParam));
 
@@ -163,6 +169,7 @@ public:
 
     void clear()
     {
+        forwarder = AudioProcessor::ParameterChangeForwarder { nullptr };
         ownedGroup = AudioProcessorParameterGroup();
         params.clear();
     }
@@ -211,6 +218,7 @@ private:
     const AudioProcessorParameterGroup* processorGroup = nullptr;
     AudioProcessorParameterGroup ownedGroup;
     Array<AudioProcessorParameter*> params;
+    AudioProcessor::ParameterChangeForwarder forwarder { nullptr };
     bool legacyParamIDs = false, usingManagedParameters = false;
 };
 

modules/juce_audio_processors/processors/juce_AudioProcessor.cpp

@@ -521,7 +521,7 @@ void AudioProcessor::addParameter (AudioProcessorParameter* param)
     jassert (param != nullptr);
     parameterTree.addChild (std::unique_ptr<AudioProcessorParameter> (param));
 
-    param->processor = this;
+    param->setOwner (&parameterListener);
     param->setParameterIndex (flatParameterList.size());
     flatParameterList.add (param);
 
@@ -539,7 +539,7 @@ void AudioProcessor::addParameterGroup (std::unique_ptr<AudioProcessorParameterG
     for (int i = oldSize; i < flatParameterList.size(); ++i)
     {
         auto p = flatParameterList.getUnchecked (i);
-        p->processor = this;
+        p->setOwner (&parameterListener);
         p->setParameterIndex (i);
 
         validateParameter (p);
@@ -566,7 +566,7 @@ void AudioProcessor::setParameterTree (AudioProcessorParameterGroup&& newTree)
     for (int i = 0; i < flatParameterList.size(); ++i)
     {
         auto p = flatParameterList.getUnchecked (i);
-        p->processor = this;
+        p->setOwner (&parameterListener);
         p->setParameterIndex (i);
 
         validateParameter (p);
@@ -1423,6 +1423,31 @@ AudioProcessorParameter* AudioProcessor::getParamChecked (int index) const
 bool AudioProcessor::canAddBus ([[maybe_unused]] bool isInput) const                     { return false; }
 bool AudioProcessor::canRemoveBus ([[maybe_unused]] bool isInput) const                  { return false; }
 
+//==============================================================================
+void AudioProcessor::ParameterChangeForwarder::parameterValueChanged (int index, float value)
+{
+    if (owner == nullptr)
+        return;
+
+    for (int i = owner->listeners.size(); --i >= 0;)
+        if (auto* l = owner->listeners[i])
+            l->audioProcessorParameterChanged (owner, index, value);
+}
+
+void AudioProcessor::ParameterChangeForwarder::parameterGestureChanged (int index, bool begin)
+{
+    if (owner == nullptr)
+        return;
+
+    const auto callback = begin
+                        ? &AudioProcessorListener::audioProcessorParameterChangeGestureBegin
+                        : &AudioProcessorListener::audioProcessorParameterChangeGestureEnd;
+
+    for (int i = owner->listeners.size(); --i >= 0;)
+        if (auto* l = owner->listeners[i])
+            (l->*callback) (owner, index);
+}
+
 JUCE_END_IGNORE_DEPRECATION_WARNINGS
 
 } // namespace juce

modules/juce_audio_processors/processors/juce_AudioProcessor.h

@@ -1516,6 +1516,31 @@ public:
     [[deprecated]] virtual bool isOutputChannelStereoPair (int index) const;
     /** @endcond */
 
+    /** @internal
+        Used to convert new-style per-parameter callbacks into old-style processor-change
+        callbacks.
+        This type will be removed in the future!
+    */
+    class ParameterChangeForwarder : public AudioProcessorParameter::Listener
+    {
+    public:
+        explicit ParameterChangeForwarder (AudioProcessor* o) : owner (o) {}
+
+        ParameterChangeForwarder (const ParameterChangeForwarder& other) : owner (other.owner) {}
+
+        ParameterChangeForwarder& operator= (const ParameterChangeForwarder& other)
+        {
+            owner = other.owner;
+            return *this;
+        }
+
+        void parameterValueChanged (int, float) override;
+        void parameterGestureChanged (int, bool) override;
+
+    private:
+        AudioProcessor* owner = nullptr;
+    };
+
 private:
     //==============================================================================
     struct InOutChannelPair
@@ -1588,6 +1613,8 @@ private:
     AudioProcessorParameterGroup parameterTree;
     Array<AudioProcessorParameter*> flatParameterList;
 
+    ParameterChangeForwarder parameterListener { this };
+
     AudioProcessorParameter* getParamChecked (int) const;
 
   #if JUCE_DEBUG

modules/juce_audio_processors/processors/juce_AudioProcessorEditor.h

@@ -36,6 +36,7 @@ namespace juce
 {
 
 class AudioProcessorEditorListener;
+class AudioProcessor;
 
 //==============================================================================
 /**

modules/juce_audio_processors/processors/juce_AudioProcessorParameter.cpp

@@ -50,6 +50,12 @@ void AudioProcessorParameter::setParameterIndex (int index) noexcept
     parameterIndex = index;
 }
 
+void AudioProcessorParameter::setOwner (Listener* listenerIn) noexcept
+{
+    jassert (finalListener == nullptr);
+    finalListener = listenerIn;
+}
+
 void AudioProcessorParameter::setValueNotifyingHost (float newValue)
 {
     setValue (newValue);
@@ -59,7 +65,7 @@ void AudioProcessorParameter::setValueNotifyingHost (float newValue)
 void AudioProcessorParameter::beginChangeGesture()
 {
     // This method can't be used until the parameter has been attached to a processor!
-    jassert (processor != nullptr && parameterIndex >= 0);
+    jassert (parameterIndex >= 0);
 
    #if JUCE_DEBUG && ! JUCE_DISABLE_AUDIOPROCESSOR_BEGIN_END_GESTURE_CHECKING
     // This means you've called beginChangeGesture twice in succession without
@@ -75,20 +81,14 @@ void AudioProcessorParameter::beginChangeGesture()
         if (auto* l = listeners[i])
             l->parameterGestureChanged (getParameterIndex(), true);
 
-    if (processor != nullptr && parameterIndex >= 0)
+    if (finalListener != nullptr)
-    {
+        finalListener->parameterGestureChanged (getParameterIndex(), true);
-        // audioProcessorParameterChangeGestureBegin callbacks will shortly be deprecated and
-        // this code will be removed.
-        for (int i = processor->listeners.size(); --i >= 0;)
-            if (auto* l = processor->listeners[i])
-                l->audioProcessorParameterChangeGestureBegin (processor, getParameterIndex());
-    }
 }
 
 void AudioProcessorParameter::endChangeGesture()
 {
     // This method can't be used until the parameter has been attached to a processor!
-    jassert (processor != nullptr && parameterIndex >= 0);
+    jassert (parameterIndex >= 0);
 
    #if JUCE_DEBUG && ! JUCE_DISABLE_AUDIOPROCESSOR_BEGIN_END_GESTURE_CHECKING
     // This means you've called endChangeGesture without having previously
@@ -104,14 +104,8 @@ void AudioProcessorParameter::endChangeGesture()
         if (auto* l = listeners[i])
             l->parameterGestureChanged (getParameterIndex(), false);
 
-    if (processor != nullptr && parameterIndex >= 0)
+    if (finalListener != nullptr)
-    {
+        finalListener->parameterGestureChanged (getParameterIndex(), false);
-        // audioProcessorParameterChangeGestureEnd callbacks will shortly be deprecated and
-        // this code will be removed.
-        for (int i = processor->listeners.size(); --i >= 0;)
-            if (auto* l = processor->listeners[i])
-                l->audioProcessorParameterChangeGestureEnd (processor, getParameterIndex());
-    }
 }
 
 void AudioProcessorParameter::sendValueChangedMessageToListeners (float newValue)
@@ -122,14 +116,8 @@ void AudioProcessorParameter::sendValueChangedMessageToListeners (float newValue
         if (auto* l = listeners [i])
             l->parameterValueChanged (getParameterIndex(), newValue);
 
-    if (processor != nullptr && parameterIndex >= 0)
+    if (finalListener != nullptr)
-    {
+        finalListener->parameterValueChanged (getParameterIndex(), newValue);
-        // audioProcessorParameterChanged callbacks will shortly be deprecated and
-        // this code will be removed.
-        for (int i = processor->listeners.size(); --i >= 0;)
-            if (auto* l = processor->listeners[i])
-                l->audioProcessorParameterChanged (processor, getParameterIndex(), newValue);
-    }
 }
 
 bool AudioProcessorParameter::isOrientationInverted() const                      { return false; }

modules/juce_audio_processors/processors/juce_AudioProcessorParameter.h

@@ -35,8 +35,6 @@
 namespace juce
 {
 
-class AudioProcessor;
-
 //==============================================================================
 /** An abstract base class for parameter objects that can be added to an
     AudioProcessor.
@@ -264,9 +262,9 @@ public:
 
     /** @internal
         This should only be called by the owner of the parameter after it has been added to
-        a processor. Do not call this function; changing parameter indices *will* break things!
+        a processor. Do not call this function; changing the parameter index *will* break things!
     */
-    void setParameterIndex (int index) noexcept;
+    void setParameterIndex (int) noexcept;
 
     //==============================================================================
     /** Returns the current value of the parameter as a String.
@@ -338,6 +336,12 @@ public:
         virtual void parameterGestureChanged (int parameterIndex, bool gestureIsStarting) = 0;
     };
 
+    /** @internal
+        This should only be called by the owner of the parameter after it has been added to
+        a processor. Do not call this function; changing the owner *will* break things!
+    */
+    void setOwner (Listener* listener) noexcept;
+
     /** Registers a listener to receive events when the parameter's state changes.
         If the listener is already registered, this will not register it again.
 
@@ -355,9 +359,6 @@ public:
     /** @internal */
     void sendValueChangedMessageToListeners (float newValue);
 
-    /** @internal */
-    AudioProcessor* processor = nullptr;
-
     /** Returns the default number of steps for a parameter.
 
         NOTE! This method is deprecated! It's recommended that you use
@@ -373,6 +374,7 @@ private:
     int version = 0;
     CriticalSection listenerLock;
     Array<Listener*> listeners;
+    Listener* finalListener = nullptr;
     mutable StringArray valueStrings;
 
    #if JUCE_DEBUG