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Date: Wed, 24 Jul 2013 20:02:00 +0100
Message-ID: <CAD_DGvkDNJdx6+3bqfeqSbpueCxG=i69dBysVd6w+4QroeqZ-g@mail.gmail.com>
Subject: Re: [geda-user] Non-modal Dialogs
From: Luis de Arquer <dearquerfern AT gmail DOT com>
To: geda-user AT delorie DOT com
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On Tue, Jul 23, 2013 at 1:29 AM, Edward Hennessy <ehennes AT sbcglobal DOT net> wrote:
>
> On Jul 22, 2013, at 11:01 AM, Luis de Arquer <dearquerfern AT gmail DOT com> wrote:
>>
>> So my suggestion is, why not use the weak refs to implement Stefan's
>> idea? Right now, it only notifies destruction of the object -correct
>> me if I am wrong-, but it could well notify a change in the object.
>> So, in the case of the properties dialog, on creation it would create
>> a weak ref to the object, with a notification callback. And everytime
>> an object is modified, the list of weak refs is checked, calling any
>> existing callback.
>
> Thanks. I will look at the weak references.
>
> Cheers,
> Ed


Having a quick look at libgeda/src/s_weakref.c, there are a few
functions managing the notification, and helping to add weak
references to an object (weak references are stored in a GList at
st_object). It is the only notifying mechanism I have found in libgeda
so far. The weak ref struct looks like this:

struct WeakRef
{
  void (*notify_func)(void *, void *);
  void *user_data;
};

so it is a simple notification mechanism, apparently only used for
object destruction, although it could potentially be used for other
events.

IMHO, gobjects may be a better long term choice. It has most of the
job done already, and includes reference counting. It is also
attribute friendly, but I don't know how much of a grief it could be
to embed gobjects in libgeda.

Regards,
Luis