private :

    friend class RenderTarget;

////////////////////////////////////////////////////////////
/// Draw the object into the specified window
///
/// param Target : Target into which render the object
///
////////////////////////////////////////////////////////////
void Draw(RenderTarget& Target) const;

////////////////////////////////////////////////////////////
/// Render the specific geometry of the object
///
/// param Target : Target into which render the object
///
////////////////////////////////////////////////////////////
virtual void Render(RenderTarget& Target) const = 0;

class MyDrawable : public sf::Drawable {

private:

    virtual void Render(RenderTarget& target) const {
        // Do some rendering of whatever...
        target.Draw(mySubSprite);
    }

    sf::Sprite mySubSprite;

};

class MyDrawable : public sf::Drawable
{
public :

   ...

private :

    virtual void Render(sf::RenderTarget& target, sf::Renderer& renderer) const
    {
        // Low-level geometry rendering
        renderer.SetTexture(&myTexture);
        renderer.Begin(sf::Renderer::QuadList);
            renderer.AddVertex(...);
            renderer.AddVertex(...);
            renderer.AddVertex(...);
            renderer.AddVertex(...);
        renderer.End();

        // High-level drawable rendering
        target.Draw(mySubSprite);
    }

    sf::Image myTexture;
    sf::Sprite mySubSprite;
};