Basic VU meter hookup

IPlugEffect.cpp

#include "IPlugEffect.h"
#include "IPlug_include_in_plug_src.h"
#include "IControls.h"

constexpr int kNumVUFrames = 100;

IPlugEffect::IPlugEffect(const InstanceInfo& info)
: Plugin(info, MakeConfig(kNumParams, kNumPresets))
{
  GetParam(kGain)->InitDouble("Gain", 0., 0., 100.0, 0.01, "%");

  mMakeGraphicsFunc = [&]() {
    return MakeGraphics(*this, PLUG_WIDTH, PLUG_HEIGHT, PLUG_FPS);
  };
  
  mLayoutFunc = [&](IGraphics* pGraphics) {
    pGraphics->AttachPanelBackground(COLOR_GRAY);
    pGraphics->AttachControl(new IBitmapControl(100, 100, pGraphics->LoadBitmap(VU2X_FN, kNumVUFrames)), kCtrlTagVUMeter);
  };
} 

void IPlugEffect::OnIdle()
{
  SendControlValueFromDelegate(kCtrlTagVUMeter, mLevel.load());
}

void IPlugEffect::ProcessBlock(sample** inputs, sample** outputs, int nFrames)
{
  const double gain = GetParam(kGain)->Value() / 100.;
  const int nChans = NOutChansConnected();
  
  for (int s = 0; s < nFrames; s++) {
    for (int c = 0; c < nChans; c++) {
      outputs[c][s] = inputs[c][s];
    }
  }

  mLevel.store(outputs[0][0]);
}

IPlugEffect.h

#pragma once

#include "IPlug_include_in_plug_hdr.h"

const int kNumPresets = 1;
constexpr int kCtrlTagVUMeter = 0;

enum EParams
{
  kGain = 0,
  kNumParams
};

using namespace iplug;
using namespace igraphics;

class IPlugEffect final : public Plugin
{
public:
  IPlugEffect(const InstanceInfo& info);
  void OnIdle() override;
  void ProcessBlock(sample** inputs, sample** outputs, int nFrames) override;

  std::atomic<float> mLevel;
};