Custom Visibility Modifiers in C++ -

i reading signals & slots | qt core 5.4 , had following code snipped.

#include <qobject>  class counter : public qobject {     q_object  public:     counter() { m_value = 0; }      int value() const { return m_value; }  public slots:     void setvalue(int value);  signals:     void valuechanged(int newvalue);  private:     int m_value; }; 

i have seen private, public, , protected before never this.

• what going on whole public slots: , signals: visibility modifiers (is called)?

• what mean , in standard talk this?

• when can / should use these in own code?

slots signals evaluate empty strings or modifiers , defined implicitly including qobject.h. these markers qt moc (meta object compiler). q_object being expanded generic qt-class interface.

the moc generate code header , these macros provide information 'these methods slots' or 'this going qt-ified class'

you should use them in qt-projects , case develop class 'become' , deal qt objects. examples own qt-widgets or object should able send/receive signals.

you won't find in standard these macros because not part of it. it's extension qt-framework , able compile classes when include appropriate qt header files.