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

Subject: Re: [boost] Interest in non-intrusive signal/slot lib?
From: Peter Dimov (lists_at_[hidden])
Date: 2015-05-20 11:32:51

Edward Diener wrote:
> This is similar to the way in the signals2 library that one has to have 
> access to a boost::signals2::signal in order to setup a connection to a 
> slot. So while I like your library I do not immediately understand the 
> advantage it has over signals2.

When you already have an existing third-party object (say, XButton) it's 
more convenient to not have to think where to place the corresponding signal 
object. Non-intrusive dispatch is kind of like the library containing the 
equivalent of map<void*, signal>, automatically managing the signal objects 
corresponding to an external, third-party, object.

In the use case in which you define your buttons, there's not much to gain, 
you make them contain your signal objects. But third-party buttons don't 
contain your signal objects, they contain their own functionality for 
notifying you of events, sometimes that's (their own) signal implementation, 
sometimes a callback/std::function, sometimes you need to override a virtual 
method, sometimes they send you messages. With a non-intrusive signal 
library, you just attach an emit call to the third-party notification 
mechanism and the rest of the code can connect to the non-intrusive signal. 
This avoids the need to wrap the external objects in your own types that 
contain signal objects.