Re: [gtkmm] Signal emission stop

["Andrew E. Makeev" <andrew solvo ru>]

Martin Schulze wrote:

> Am 2003.04.23 13:41 schrieb(en) Andrew E. Makeev:
>
> > Hi,
> >
> > Look at the simple example below, and explain, please, how could I 
> > stop SigC signal emission?
>
>
> For gtk(mm) signals the signal emission can be stopped by returning true
> (or was it false? => we have to look at the docs!) in the signal handler. 

Yes, it should be true for <signal_..._event>, and 
<signal>.emission_stop () for named GTK signals.

> For you own SigC signals you need a Marshaller (see marshal.h) to
> achieve the same:
>
>   class MyMarshal  {
>     // both typedefs must be defined.
>     typedef bool InType;
>     typedef bool OutType;
>
>   public:
>     OutType stopped_emission;
>
>     // Return final return code.
>     OutType value()
>       { return stopped_emission; }
>
>     // Captures return codes and returns TRUE to stop emission.
>     bool marshal(const InType& stop_emission)
>       { stopped_emission=stop_emission; return stop_emission; }
>
>     MyMarshal() : stopped_emission(false) {}
>   };
>
>
> Your example would read:
>
>   class MyClass : public SigC::Object {
>   public:
>     ...
>     SigC::Signal0<bool,MyMarshal> test_signal;
>     ...
>   };
>
>   void MyClass::some_method () {
>     test_signal.connect (SigC::slot (*this, &MyClass::f1));
>     test_signal.connect (SigC::slot (*this, &MyClass::f2));
>   }
>
>   bool MyClass::f1 () {
>     if (<expr> == true)
>       return true;  // return true to stop emission. function f2 won't 
> be called
>     else
>       return false;  // continue signal emission
>   }
>
>   bool MyClass::f2 () {
>     return false;
>   }
Thanks a lot, everything works great now, just when I added 
MyMarshal::default_value () method :).

Regards,
-andrew