Decorator design pattern ( C++ )

#include <iostream>

using namespace std;

/* Component (interface) */
class Widget {

public:
  virtual void draw() = 0;
  virtual ~Widget() {}
};

/* ConcreteComponent */
class TextField : public Widget {

private:
   int width, height;

public:
   TextField( int w, int h ){
      width = w;
      height = h;
   }
  void draw() {
      cout << "TextField: " << width << ", " << height << '\n';
   }
};

/* Decorator (interface) */
class Decorator : public Widget {

private:
   Widget* wid; // reference to Widget
public:
   Decorator( Widget* w ) {
     wid = w;
   }
void draw() {
     wid->draw();
   }

~Decorator() {
     delete wid;
   }
};

/* ConcreteDecoratorA */
class BorderDecorator : public Decorator {

public:
   BorderDecorator( Widget* w ) : Decorator( w ) { }
   void draw() {
      Decorator::draw();
      cout << " BorderDecorator" << '\n';
   }
};

/* ConcreteDecoratorB */
class ScrollDecorator : public Decorator {
public:
   ScrollDecorator( Widget* w ) : Decorator( w ) { }
   void draw() {
      Decorator::draw();
      cout << " ScrollDecorator" << '\n';
   }
};

int main( void ) {

   Widget* aWidget = new BorderDecorator( new ScrollDecorator( new
TextField( 80, 24 )));

   aWidget->draw();

   delete aWidget;
}

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How does interface property changes here ?

it will call draw( ) function in following order
   1. TextField
   2. ScrollDecorator
   3. BorderDecorator

Is it Following RAII( Resource Acquisition is Order of
initialization ) principle of C++ ?

How are virtual function helping it ?

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