Re: [boost] Interest in non-intrusive signal/slot lib?

Subject: Re: [boost] Interest in non-intrusive signal/slot lib?
From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2015-05-16 15:04:35

On Sat, May 16, 2015 at 11:50 AM, Edward Diener <eldiener_at_[hidden]>
wrote:

>  I assume that the purpose of having the signal type be a pointer to a
>>> function taking some data and returning an incomplete type instead of
>>> returning void is to make each signal type unique. But is this really
>>> necessary ?
>>>
>>
>> It is necessary so that if you have:
>>
>> typedef struct button_down_(*button_down)(int x, int y);
>>
>> you can tell it apart from
>>
>> typedef struct button_up_(*button_up)(int x, int y);
>>
>>
> I understand that the types are different but when would you ever use that
> knowledge in code ?

It seems you're asking why are different signals necessary, e.g. why would
I need to discriminate between a "button down" and a "button up" event --
which is puzzling. Anyway, the answer is that you need different signals so
that you can tell connect<> which signal you're connecting (and emit<>
which signal you're emitting) from the specified emitter object:

void handle_button_down( int x, int y );
void handle_button_up( int x, int y );

auto c1=connect<button_down>(e,&handle_button_down);
auto c2=connect<button_up>(e,&handle_button_up);

> The signal handler knows nothing about the type of the signal except that
> it's signature matches the parameters of the signal.

The signal handling code knows nothing about signals at all.

-- 
Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode