Re: [boost] Re: Re: Re: Java style GUI in C++

From: Mathew Robertson (mathew.robertson_at_[hidden])
Date: 2004-08-22 18:59:38

> >>> It might be easier to group events by type, use signals to dispatch
> >>> them and an event handler like I suggested to deal with them, e.g.
> >>>    MouseEvent( unsigned int event, const MouseEvent & info );
> >>>    KeyEvent( unsigned int event, const KeyEvent & info );
> >>
> >> Why do you have to create event handlers for people to use. Just
> >> create boost::signal<> which encapsulates the parameters you want to
> >> pass when the event occurs. Give it a name which relates to the
> >> event that is happening, and let anyone simply add their slot to the
> >> signal. When your code determines that the event has occurred, just
> >> trigger the signal and allow anyone, including your own internal
> >> code if necessary, to handle the event. Why do I like this ? Because
> >> systems that determine that one must be this-or-that to handle an
> >> event are always unnecessarily limiting in one way or another.
> >
> > The problem with the "registering your self in a slot" approach, is
> > that most events generate actions -> ie they application flow is
> > bi-directional.  The signal/slot approach (usually) suffers from not
> > being able to send a response back to the event sender.
> 
> The boost::signal<> is fully capable of returning a response. Take a look at
> it. Furthermore even if it weren't, it is child's play to pass a reference
> or pointer to something in which a response is put. Finally any handler of a
> boost::signal<> can generate their own event in response themselves.

Exactly - but how many GUI toolkits actually make the API for the sender of the event, pass a reference to itself?  Having myself had a look a little while ago, there arn't many.

... which was the point I was trying to highlight -> I must articulated myself correctly.

Mathew