Re: [gtkmm] Signal emission stop

[MHL Schulze t-online de (Martin Schulze)]

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.

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;
  }


Cheers,

  Martin