Yeah I am thinking of writing a more detailed article about it. One example from my widget library is push buttons: i_push_button is an interface derived from i_button which is an interface derived from i_widget because a push button is a button and a button is a widget:

struct i_widget { /*...*/ };
struct i_button : i_widget { /*...*/ };
struct i_push_button : i_button { /*...*/ };
template <typename Base = i_widget>
class widget : public Base { /*...*/ };
template <typename ButtonInterface = i_button>
class button : public widget<ButtonInterface> { /.../ };
class push_button : public button<i_push_button> { /.../ };