QuickMessage.md

public FormsView
{
  Func<Point, bool> _setInitialTransformationCallBack;
  
  // could hide this behind explicit interface
  public void RegisterCallBack(Func<Point, bool> callback)
  {
    _setInitialTransformationCallBack = callback;
  }
  
  public bool SetInitialTransformation(Point screenLocation)
  {
      return _setInitialTransformationCallBack(screenLocation);
  }
}

public abstract class RendererBase
{
  public void OnElementChanged(FormsView view)
  {
      view.RegisterCallBack(SetInitialTransformation);
  }
  
  public abstract bool SetInitialTransformation(Point screenLocation);
}