Re: Removing widgets in the main loop from another thread

[Damon Register <damon w register lmco com>]

Chris Vine wrote:
> object whose method is being executed via Glib::Dispatcher.  Deriving
> that object from sigc::trackable would avoid executing (via a signal)
> one of its non-static methods after it has ceased to exist; but it would
> not prevent a segfault when the main loop tries to look-up the (by then
> not-existing) Glib::Dispatcher object to try to execute the signal
> object it used to keep.
>
> See this for further discussion:
>
> http://mail.gnome.org/archives/gtkmm-list/2008-January/msg00048.html
I am working on a small test app in order to understand how to use
Glib::Thread.  I have read the Glib::Thread reference at
http://www.gtkmm.org/docs/glibmm-2.4/docs/reference/html/classGlib_1_1Thread.html
and have also found a few gtkmm-list discussions such as this one.
The problem is that I am still struggling to understand the issue with
sigc::trackable not being thread safe.

In this example at
http://www.gtkmm.org/docs/glibmm-2.4/docs/reference/html/thread_2thread_8cc-example.html
I see that MessageQueue is derived from sigc::trackable.  This appears to
be a violation of what the class ref says

   Because sigc::trackable is not thread safe, if the slot represents a non-static class
   method (that is, it is created by sigc::mem_fun()), the class concerned should not
   derive from sigc::trackable.

Is the example program thread safe?  If it is thread safe, how is this
not a violation of what the class ref says?  How would I change it
to be unsafe?  Certainly I don't want to do that but I want to understand
what not to do.

If the example is not thread safe, how would it be change to be safe?

Damon Register