irr::u32 oldState = 0;
bool CApplication::OnEvent(const irr::SEvent &event)
{
    ... bla bla
    if(event. ... == ...JOYSTIC_EVENT)
    {
        irr::u32 tmp = oldState ^ event. ... .ButtonStates;
        
        if((tmp & 0b00001) & event. ... .ButtonStates)
            ... bla bla du bouton 1
            
        oldState = event. ... .ButtonStates;
        
    }
    ... bla bla
}