是否可以使用boost.statecharts自定义对处于不同正交区域的多个状态下的事件进行反应？

Question

我的用例类似于这个SSCCE。问题是，如果没有发生转换，我需要转发事件，这似乎不自然，因为它们将被其他正交区域处理。但更重要的是，在我需要转换的情况下，我找不到一种方法来允许事件在其他区域做出反应。我应该如何重构来解决这个问题呢？

我使用的是boost 1.53，以防这很重要。

namespace sc = boost::statechart;
struct Active;
struct Keyboard : sc::state_machine< Keyboard, Active > {};

struct NumLockOff;
struct CapsLockOff;
struct ScrollLockOff;
struct Active: sc::simple_state< Active, Keyboard, boost::mpl::list< NumLockOff, CapsLockOff, ScrollLockOff > > {};

struct EvNumLockPressed : sc::event< EvNumLockPressed > {};
struct EvCapsLockPressed : sc::event< EvCapsLockPressed > {};
struct EvScrollLockPressed : sc::event< EvScrollLockPressed > {};
struct EvAllLocksOffPressed : sc::event< EvAllLocksOffPressed > {
    int i_;
    EvAllLocksOffPressed(int i):sc::event< EvAllLocksOffPressed >(),i_(i){}
};

struct NumLockOn : sc::simple_state< NumLockOn, Active::orthogonal< 0 > >
{
    typedef boost::mpl::list<sc::transition< EvNumLockPressed, NumLockOff >, sc::custom_reaction<EvAllLocksOffPressed>> reactions;
    sc::result react( const EvAllLocksOffPressed & e)
    {
        if(e.i_ == 42)
            return transit< NumLockOff >();
        return forward_event();
    }
};

struct NumLockOff : sc::simple_state< NumLockOff, Active::orthogonal< 0 > >
{
    typedef sc::transition< EvNumLockPressed, NumLockOn > reactions;
};

struct CapsLockOn : sc::simple_state< CapsLockOn, Active::orthogonal< 1 > >
{
    typedef boost::mpl::list<sc::transition< EvCapsLockPressed, CapsLockOff >, sc::custom_reaction<EvAllLocksOffPressed>> reactions;
    sc::result react( const EvAllLocksOffPressed & e)
    {
        if(e.i_ == 42)
            return transit< CapsLockOff >();
        return forward_event();
    }
};

struct CapsLockOff : sc::simple_state< CapsLockOff, Active::orthogonal< 1 > >
{
    typedef sc::transition< EvCapsLockPressed, CapsLockOn > reactions;
};

struct ScrollLockOn : sc::simple_state< ScrollLockOn, Active::orthogonal< 2 > >
{
    typedef boost::mpl::list<sc::transition< EvScrollLockPressed, ScrollLockOff >, sc::custom_reaction<EvAllLocksOffPressed>> reactions;
    sc::result react( const EvAllLocksOffPressed & e)
    {
        if(e.i_ == 42)
            return transit< ScrollLockOff >();
        return forward_event();
    }
};

struct ScrollLockOff : sc::simple_state< ScrollLockOff, Active::orthogonal< 2 > >
{
    typedef sc::transition< EvScrollLockPressed, ScrollLockOn > reactions; 
};

int main(){
    Keyboard k;
    k.initiate();
    k.process_event(EvNumLockPressed());
    k.process_event(EvCapsLockPressed());
    k.process_event(EvScrollLockPressed());
    k.process_event(EvAllLocksOffPressed(1));
    k.process_event(EvAllLocksOffPressed(42));
}

Answer 1

这个问题是由库的作者answered提出的。他指的是Event dispatch to orthogonal regions。