Rubbery-like-cables in Iplug2. Based on code https://gist.github.com/olilarkin/a4bb2552744001a677bd56160884b35c by @olilarkin

IPlugEffect.cpp

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

constexpr auto CN = 30;
struct Cable
{
  IVec2 pos1;
  IVec2 pos2;
  IColor color;

  Cable(float x, float y, const IColor& color)
    : pos1(x, y)
    , pos2(x + 1, y + 1)
    , color(color)
  {
  }
};

class CableControl : public IControl
{
private:
  WDL_PtrList<Cable> mCables;

public:
  CableControl(const IRECT& bounds)
    : IControl(bounds)
  {
    mIgnoreMouse = true;
  }

  ~CableControl()
  {
    mCables.Empty(true);
  }

  void Draw(IGraphics& g) override
  {
    for (int i = 0; i < mCables.GetSize(); i++)
    {
      DrawCable(g, mCables.Get(i));
    }
  }

  Cable* AddCable(float x, float y, const IColor& color)
  {
    Cable* pNewCable = mCables.Add(new Cable(x, y, color));
    SetDirty(false);
    return pNewCable;
  }

  void RemoveCable(Cable* pCable)
  {
    mCables.DeletePtr(pCable, true);
    SetDirty(false);
  }

private:
  void DrawCable(IGraphics& g, Cable* cable)
  {
    float d = (abs(cable->pos1.x - cable->pos2.x) + abs(cable->pos1.y - cable->pos2.y)) *0.25;
    
    g.PathMoveTo(cable->pos1.x, cable->pos1.y+5);
    g.PathCubicBezierTo(cable->pos1.x, cable->pos1.y + d+ 5, cable->pos2.x, cable->pos2.y + d+5, cable->pos2.x, cable->pos2.y+5);
    g.PathStroke(COLOR_BLACK_DROP_SHADOW.WithOpacity(0.2), 8.f);

    g.PathMoveTo(cable->pos1.x, cable->pos1.y);
    g.PathCubicBezierTo(cable->pos1.x, cable->pos1.y + d+5, cable->pos2.x, cable->pos2.y + d+5, cable->pos2.x, cable->pos2.y);
    g.PathStroke(cable->color, 6.f);
    g.FillCircle(cable->color, cable->pos1.x, cable->pos1.y, 5);
    g.FillCircle(cable->color, cable->pos2.x, cable->pos2.y, 5);
  }

};

class PlugControl : public IControl
{
public:
  PlugControl(const IRECT& bounds, CableControl* pCableControl)
    : IControl(bounds)
    , mCableControl(pCableControl)
  {}

  void Draw(IGraphics& g) override
  {
    g.FillEllipse(COLOR_RED, mRECT);

    if (mMouseIsOver || mAboutToConnect)
    {
      g.DrawEllipse(COLOR_BLACK, mRECT, 0, 3);
    }
  }

  void OnMouseDown(float x, float y, const IMouseMod& mod) override
  {
    
    mLastCable = mCableControl->AddCable(mRECT.MW(), mRECT.MH(), COLOR_RED.GetRandomColor());
  }

  void OnMouseUp(float x, float y, const IMouseMod& mod) override
  {
    bool valid = false;
    for (int i = 0; i < CN; i++)
    {
      PlugControl* pPlug = GetUI()->GetControlWithTag(i)->As<PlugControl>();
      if (pPlug != this)
        valid |= pPlug->GetRECT().Contains(x, y);
    }

    if (!valid) {
      mCableControl->RemoveCable(mLastCable);
    }
    

    mLastCable = nullptr;
  }

  void OnMouseDrag(float x, float y, float dX, float dY, const IMouseMod& mod) override
  {
    if (mLastCable) {
      mLastCable->pos2 = { x, y };

      for (int i = 0; i < CN; i++)
      {
        PlugControl* pPlug = GetUI()->GetControlWithTag(i)->As<PlugControl>();
        pPlug->mAboutToConnect = pPlug->GetRECT().Contains(x, y);
      }

      mCableControl->SetDirty(false);
    }
  }

  bool mAboutToConnect = false;

private:
  Cable* mLastCable = nullptr;
  CableControl* mCableControl = nullptr;
  
};


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

#if IPLUG_EDITOR // http://bit.ly/2S64BDd
  mMakeGraphicsFunc = [&]() {
    return MakeGraphics(*this, PLUG_WIDTH, PLUG_HEIGHT, PLUG_FPS, GetScaleForScreen(PLUG_HEIGHT));
  };

  mLayoutFunc = [&](IGraphics* pGraphics) {
    pGraphics->AttachCornerResizer(EUIResizerMode::Scale, false);
    pGraphics->AttachPanelBackground(COLOR_GRAY);
    pGraphics->EnableMouseOver(true);
    pGraphics->LoadFont("Roboto-Regular", ROBOTO_FN);
    const IRECT b = pGraphics->GetBounds();
    CableControl* pCableControl = new CableControl(b);
     IRECT base = IRECT(0, 0, 20, 20).GetTranslated(200, 50);
     float off = b.H() / (CN / 2);
    for (size_t i = 0; i < CN / 2; i++)
    {
      pGraphics->AttachControl(new PlugControl(base.GetTranslated(50+(i*3), i * off), pCableControl), i);
    } for (size_t i = 0; i < CN / 2; i++)
    {
      pGraphics->AttachControl(new PlugControl(base.GetTranslated(200- (i * 3), i * off), pCableControl), CN/2+i);
    }

   
    

    pGraphics->AttachControl(pCableControl);
  };
#endif
}

#if IPLUG_DSP
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] * gain;
    }
  }
}
#endif