Re: Why can't information be passed using the Dispatcher?

On Thu, 17 Sep 2020 13:48:55 -0400
Jackson Campolattaro via gtkmm-list <gtkmm-list gnome org> wrote:

`Glib::Dispatcher` has syntax similar to a void signal, but there are cases
where it would be convenient to pass information between threads using the
same syntax. Obviously returning anything would be impossible, but is there
a technical reason not to have one way communication (e.g.
`Glib::Dispatcher<int>` that can be used a little like a
`sigc::signal<void(int)>`)? Obviously the user would have to be especially
careful about scope (don't pass references to things that might be deleted
before the other thread can act on the signal). In some cases it might also
make sense to pass a mutex alongside the value.

Is this functionality not provided as part of libsigc++ just because it's
unsafe-by-default, or is there a deeper problem? According to this old
thread <>,
libsigcX <> provides something
similar, but it looks like it hasn't been updated in a very long time.

If there's not an obvious issue that makes it impossible, I'll probably
write myself a wrapper class that gives me this kind of behavior.

Glib::Dispatcher uses a pipe to synchronize between threads.  You could
possibly serialize objects and send them over the pipe in a C++
standard non-conforming way (that would work with an int) but why
bother?  Just use an asynchronous queue as suggested, which is pretty
much fool-proof and will work with non-trivial objects (using "trivial"
in its C++-standard sense).

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