Midi keyboard callbacks not working

I am trying to learn how to read midi keyboard keystrokes in a VST plugin. I’m creating a basic plugin project, but for some reason I can’t get callbacks for handleIncomingMidiMessage, handleNoteOn and handleNoteOff, as in the project from the tutorial. Why?

In PluginProcessor.h, I added:

class NewProjectAudioProcessor  :   public juce::AudioProcessor,
                                    public juce::Component,
                                    private juce::MidiInputCallback,
                                    private juce::MidiKeyboardStateListener
									
(....)

    void handleIncomingMidiMessage(juce::MidiInput* source, const juce::MidiMessage& message) override;
    void handleNoteOn(juce::MidiKeyboardState*, int midiChannel, int midiNoteNumber, float velocity) override;
    void handleNoteOff(juce::MidiKeyboardState*, int midiChannel, int midiNoteNumber, float /*velocity*/) override;

And in PluginProcessor.cpp added:

void NewProjectAudioProcessor::handleIncomingMidiMessage(juce::MidiInput* source, const juce::MidiMessage& message)
{
    DBG("handleIncomingMidiMessage");
}

void NewProjectAudioProcessor::handleNoteOn(juce::MidiKeyboardState*, int midiChannel, int midiNoteNumber, float velocity)
{
    DBG("handleNoteOn");
}

void NewProjectAudioProcessor::handleNoteOff(juce::MidiKeyboardState*, int midiChannel, int midiNoteNumber, float /*velocity*/)
{
    DBG("handleNoteOff");
}

Did I forget something?

Full code:

PluginProcessor.h:


#pragma once

#include <JuceHeader.h>

//==============================================================================
/**
*/
class NewProjectAudioProcessor  :   public juce::AudioProcessor,
                                    public juce::Component,
                                    private juce::MidiInputCallback,
                                    private juce::MidiKeyboardStateListener
{
public:
    //==============================================================================
    NewProjectAudioProcessor();
    ~NewProjectAudioProcessor() override;

    //==============================================================================
    void prepareToPlay (double sampleRate, int samplesPerBlock) override;
    void releaseResources() override;

   #ifndef JucePlugin_PreferredChannelConfigurations
    bool isBusesLayoutSupported (const BusesLayout& layouts) const override;
   #endif

    void processBlock (juce::AudioBuffer<float>&, juce::MidiBuffer&) override;

    //=============================MY SECTION=======================================
    void handleIncomingMidiMessage(juce::MidiInput* source, const juce::MidiMessage& message) override;
    void handleNoteOn(juce::MidiKeyboardState*, int midiChannel, int midiNoteNumber, float velocity) override;
    void handleNoteOff(juce::MidiKeyboardState*, int midiChannel, int midiNoteNumber, float /*velocity*/) override;

    //==========================END MY SECTION======================================
    juce::AudioProcessorEditor* createEditor() override;
    bool hasEditor() const override;

    //==============================================================================
    const juce::String getName() const override;

    bool acceptsMidi() const override;
    bool producesMidi() const override;
    bool isMidiEffect() const override;
    double getTailLengthSeconds() const override;

    //==============================================================================
    int getNumPrograms() override;
    int getCurrentProgram() override;
    void setCurrentProgram (int index) override;
    const juce::String getProgramName (int index) override;
    void changeProgramName (int index, const juce::String& newName) override;

    //==============================================================================
    void getStateInformation (juce::MemoryBlock& destData) override;
    void setStateInformation (const void* data, int sizeInBytes) override;

private:
    //==============================================================================
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (NewProjectAudioProcessor)
};

PluginProcessor.cpp:


#include "PluginProcessor.h"
#include "PluginEditor.h"

//==============================================================================
NewProjectAudioProcessor::NewProjectAudioProcessor()
#ifndef JucePlugin_PreferredChannelConfigurations
     : AudioProcessor (BusesProperties()
                     #if ! JucePlugin_IsMidiEffect
                      #if ! JucePlugin_IsSynth
                       .withInput  ("Input",  juce::AudioChannelSet::stereo(), true)
                      #endif
                       .withOutput ("Output", juce::AudioChannelSet::stereo(), true)
                     #endif
                       )
#endif
{
}

NewProjectAudioProcessor::~NewProjectAudioProcessor()
{
}

//==============================================================================
const juce::String NewProjectAudioProcessor::getName() const
{
    return JucePlugin_Name;
}

bool NewProjectAudioProcessor::acceptsMidi() const
{
   #if JucePlugin_WantsMidiInput
    return true;
   #else
    return false;
   #endif
}

bool NewProjectAudioProcessor::producesMidi() const
{
   #if JucePlugin_ProducesMidiOutput
    return true;
   #else
    return false;
   #endif
}

bool NewProjectAudioProcessor::isMidiEffect() const
{
   #if JucePlugin_IsMidiEffect
    return true;
   #else
    return false;
   #endif
}

double NewProjectAudioProcessor::getTailLengthSeconds() const
{
    return 0.0;
}

int NewProjectAudioProcessor::getNumPrograms()
{
    return 1;   // NB: some hosts don't cope very well if you tell them there are 0 programs,
                // so this should be at least 1, even if you're not really implementing programs.
}

int NewProjectAudioProcessor::getCurrentProgram()
{
    return 0;
}

void NewProjectAudioProcessor::setCurrentProgram (int index)
{
}

const juce::String NewProjectAudioProcessor::getProgramName (int index)
{
    return {};
}

void NewProjectAudioProcessor::changeProgramName (int index, const juce::String& newName)
{
}

//==============================================================================
void NewProjectAudioProcessor::prepareToPlay (double sampleRate, int samplesPerBlock)
{
    // Use this method as the place to do any pre-playback
    // initialisation that you need..
}

void NewProjectAudioProcessor::releaseResources()
{
    // When playback stops, you can use this as an opportunity to free up any
    // spare memory, etc.
}

#ifndef JucePlugin_PreferredChannelConfigurations
bool NewProjectAudioProcessor::isBusesLayoutSupported (const BusesLayout& layouts) const
{
  #if JucePlugin_IsMidiEffect
    juce::ignoreUnused (layouts);
    return true;
  #else
    // This is the place where you check if the layout is supported.
    // In this template code we only support mono or stereo.
    // Some plugin hosts, such as certain GarageBand versions, will only
    // load plugins that support stereo bus layouts.
    if (layouts.getMainOutputChannelSet() != juce::AudioChannelSet::mono()
     && layouts.getMainOutputChannelSet() != juce::AudioChannelSet::stereo())
        return false;

    // This checks if the input layout matches the output layout
   #if ! JucePlugin_IsSynth
    if (layouts.getMainOutputChannelSet() != layouts.getMainInputChannelSet())
        return false;
   #endif

    return true;
  #endif
}
#endif

void NewProjectAudioProcessor::processBlock (juce::AudioBuffer<float>& buffer, juce::MidiBuffer& midiMessages)
{
    juce::ScopedNoDenormals noDenormals;
    auto totalNumInputChannels  = getTotalNumInputChannels();
    auto totalNumOutputChannels = getTotalNumOutputChannels();
    //DBG("message 1");
    DBG(midiMessages.getNumEvents());

    // In case we have more outputs than inputs, this code clears any output
    // channels that didn't contain input data, (because these aren't
    // guaranteed to be empty - they may contain garbage).
    // This is here to avoid people getting screaming feedback
    // when they first compile a plugin, but obviously you don't need to keep
    // this code if your algorithm always overwrites all the output channels.
    for (auto i = totalNumInputChannels; i < totalNumOutputChannels; ++i)
        buffer.clear (i, 0, buffer.getNumSamples());

    //for (int j = 0; j < midiMessages.; ++j)
    //{
    //    auto* channelData = buffer.getWritePointer(j);
    //    DBG("message 2 " + channelData);
    //    // ..do something to the data...
    //}

    // This is the place where you'd normally do the guts of your plugin's
    // audio processing...
    // Make sure to reset the state if your inner loop is processing
    // the samples and the outer loop is handling the channels.
    // Alternatively, you can process the samples with the channels
    // interleaved by keeping the same state.
    for (int channel = 0; channel < totalNumInputChannels; ++channel)
    {
        auto* channelData = buffer.getWritePointer (channel);
        //DBG("message 2");
        // ..do something to the data...
    }
}

//=============================MY SECTION=======================================

void NewProjectAudioProcessor::handleIncomingMidiMessage(juce::MidiInput* source, const juce::MidiMessage& message)
{
    DBG("handleIncomingMidiMessage");
}

void NewProjectAudioProcessor::handleNoteOn(juce::MidiKeyboardState*, int midiChannel, int midiNoteNumber, float velocity)
{
    DBG("handleNoteOn");
}

void NewProjectAudioProcessor::handleNoteOff(juce::MidiKeyboardState*, int midiChannel, int midiNoteNumber, float /*velocity*/)
{
    DBG("handleNoteOff");
}

//==========================END MY SECTION======================================
bool NewProjectAudioProcessor::hasEditor() const
{
    return true; // (change this to false if you choose to not supply an editor)
}

juce::AudioProcessorEditor* NewProjectAudioProcessor::createEditor()
{
    return new NewProjectAudioProcessorEditor (*this);
}

//==============================================================================
void NewProjectAudioProcessor::getStateInformation (juce::MemoryBlock& destData)
{
    // You should use this method to store your parameters in the memory block.
    // You could do that either as raw data, or use the XML or ValueTree classes
    // as intermediaries to make it easy to save and load complex data.
}

void NewProjectAudioProcessor::setStateInformation (const void* data, int sizeInBytes)
{
    // You should use this method to restore your parameters from this memory block,
    // whose contents will have been created by the getStateInformation() call.
}

//==============================================================================
// This creates new instances of the plugin..
juce::AudioProcessor* JUCE_CALLTYPE createPluginFilter()
{
    return new NewProjectAudioProcessor();
}

You don’t get the MIDI messages in a plugin with those callbacks, they are intended for use with standalone applications that open a hardware MIDI input. The MIDI messages are delivered for plugins via the MidiBuffer of the processBlock call. You need to also set your plugin to accept MIDI messages.

Thanks, now I figured it out!

void NewProjectAudioProcessor::processBlock (juce::AudioBuffer<float>& buffer, juce::MidiBuffer& midiMessages)
{
    buffer.clear();

    juce::MidiBuffer processedMidi;

    for (const auto metadata : midiMessages)
    {
        auto message = metadata.getMessage();
        const auto time = metadata.samplePosition;
        DBG("Note number " << message.getNoteNumber());

        if (message.isNoteOn())
        {
            message = juce::MidiMessage::noteOn(message.getChannel(), message.getNoteNumber(), 1.0f);
        }

        processedMidi.addEvent(message, time);
    }

    midiMessages.swapWith(processedMidi);
}