JUCE/examples/audio plugin demo/Source/SinewaveSynth.h

/*
  ==============================================================================

    This file was auto-generated by the Jucer!

    It contains the basic startup code for a Juce application.

  ==============================================================================
*/


/** A demo synth sound that's just a basic sine wave.. */
class SineWaveSound : public SynthesiserSound
{
public:
    SineWaveSound() {}

    bool appliesToNote (int /*midiNoteNumber*/) override    { return true; }
    bool appliesToChannel (int /*midiChannel*/) override    { return true; }
};


//==============================================================================
/** A simple demo synth voice that just plays a sine wave.. */
class SineWaveVoice   : public SynthesiserVoice
{
public:
    SineWaveVoice()
       : currentAngle (0), angleDelta (0), level (0), tailOff (0)
    {
    }

    bool canPlaySound (SynthesiserSound* sound) override
    {
        return dynamic_cast<SineWaveSound*> (sound) != nullptr;
    }

    void startNote (int midiNoteNumber, float velocity,
                    SynthesiserSound* /*sound*/,
                    int /*currentPitchWheelPosition*/) override
    {
        currentAngle = 0.0;
        level = velocity * 0.15;
        tailOff = 0.0;

        double cyclesPerSecond = MidiMessage::getMidiNoteInHertz (midiNoteNumber);
        double cyclesPerSample = cyclesPerSecond / getSampleRate();

        angleDelta = cyclesPerSample * 2.0 * double_Pi;
    }

    void stopNote (float /*velocity*/, bool allowTailOff) override
    {
        if (allowTailOff)
        {
            // start a tail-off by setting this flag. The render callback will pick up on
            // this and do a fade out, calling clearCurrentNote() when it's finished.

            if (tailOff == 0.0) // we only need to begin a tail-off if it's not already doing so - the
                                // stopNote method could be called more than once.
                tailOff = 1.0;
        }
        else
        {
            // we're being told to stop playing immediately, so reset everything..

            clearCurrentNote();
            angleDelta = 0.0;
        }
    }

    void pitchWheelMoved (int /*newValue*/) override
    {
        // not implemented for the purposes of this demo!
    }

    void controllerMoved (int /*controllerNumber*/, int /*newValue*/) override
    {
        // not implemented for the purposes of this demo!
    }

    void renderNextBlock (AudioSampleBuffer& outputBuffer, int startSample, int numSamples) override
    {
        if (angleDelta != 0.0)
        {
            if (tailOff > 0)
            {
                while (--numSamples >= 0)
                {
                    const float currentSample = (float) (sin (currentAngle) * level * tailOff);

                    for (int i = outputBuffer.getNumChannels(); --i >= 0;)
                        outputBuffer.addSample (i, startSample, currentSample);

                    currentAngle += angleDelta;
                    ++startSample;

                    tailOff *= 0.99;

                    if (tailOff <= 0.005)
                    {
                        // tells the synth that this voice has stopped
                        clearCurrentNote();

                        angleDelta = 0.0;
                        break;
                    }
                }
            }
            else
            {
                while (--numSamples >= 0)
                {
                    const float currentSample = (float) (sin (currentAngle) * level);

                    for (int i = outputBuffer.getNumChannels(); --i >= 0;)
                        outputBuffer.addSample (i, startSample, currentSample);

                    currentAngle += angleDelta;
                    ++startSample;
                }
            }
        }
    }

private:
    double currentAngle, angleDelta, level, tailOff;
};