genCallback

@EventType("ClickEvent")
class ClickEvent : Event
{
    this(in size_t x, in size_t y)
    {
        this.x = x;
        this.y = y;
    }
    mixin basicEventType!ClickEvent;
private :
    const size_t x, y;
}

class Foo
{
    mixin genCallback!(const Foo, ClickEvent, const size_t, "x", const size_t, "y") onClicked;
    // Note: you can leave the parameters blank, if you do, then the event
    //     itself will be passed as the second parameter as const
public :
    void click(in size_t x, in size_t y)
    {
        // click stuff here
        onClicked.emit(x, y);
    }

    void onEvent(Event event)
    {
        // handle your events here
        auto dispacher = scoped!EventDispatcher(event);
        dispacher.dispatch!ClickEvent(&onClicked.dispatch);
    }
}

bool onFooClicked(in Foo sender, in size_t x, in size_t y)
{
    // do stuff here
    assert([x, y] == [4, 5]);

    // true to handle the event
    // false to propagate
    return true;
}

void main()
{
    Foo foo = new Foo();
    foo.onClicked.connect(toDelegate(&onFooClicked));
    foo.click(4,5); // callback!
}