#include <iostream>
#include <memory>
#include <string>

using namespace std;

class Event
{
public:
    string type;
    string source;

    virtual ~Event() { }
};

class KeyEvent : public Event
{
public:
    string key;
    string modifier;

    virtual ~KeyEvent() { }
};

class MouseEvent : public Event
{
public:
    string button;
    int x;
    int y;

    virtual ~MouseEvent() { }
};

void handleEvent(const KeyEvent& e)
{
    if(e.key == "SPACEBAR")
        cout << "Hello world! The Space key was pressed ;)" << endl;
}

auto_ptr<Event> generateEvent()
{
    auto_ptr<KeyEvent> ret(new KeyEvent);
    ret->type = "KEYBOARD_EVENT";
    ret->source = "Keyboard0";
    ret->key = "SPACEBAR";
    ret->modifier = "none";

    return auto_ptr<Event>(ret.release());
}

int main()
{
    auto_ptr<Event> pEvent = generateEvent();
    KeyEvent *pKeyEvent = dynamic_cast<KeyEvent*>(pEvent.get());
    if (pKeyEvent) {
        handleEvent(*pKeyEvent);
    }

    return 0;
}

Hello world! The Space key was pressed ;)