Re: [boost] enumeration interface for boost::signals

From: E. Gladyshev (eegg_at_[hidden])
Date: 2004-03-08 03:39:44

From: "Douglas Paul Gregor" <gregod_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Sunday, March 07, 2004 8:22 PM
Subject: Re: [boost] enumeration interface for boost::signals

[...]

> No, it wasn't. What sort of application do you need it for? It's
> interesting.

I am trying to use boost::signals in my GUI project.
The capturing feature is needed when
a window has many separate regions (each region is a slot)
and a region wants to capture all mouse events after the mouse enters
this region. It is a very typical situation.

The ability to enumerate slots in a defined order is
necessary for building something similar to callback chains.
For instance, in Win32 you can insert your window callback
function into the existing chain.

Something like

callback prev_cb;

void my_callback()
{
   if( some condition )
   {
      prev_cb();  //propagate the signal futher
      do_something1();
   }
  else
  {
     do_something2();
     return; //stop signal propagation
  }
}

main()
{
    window w;

    prev_cb = register_callback(w, my_callback)
}

I am not sure what's the best way to implement something like this with
boost::signals.

It seems to me that we need a finer control over the slots.

Eugene