[fpc-devel] "Signals"

[Michael Van Canneyt]

On Fri, 26 Sep 2014, Sven Barth wrote:

> 
> Am 26.09.2014 10:58 schrieb "Michael Van Canneyt" <michael at freepascal.org>:
> >
> >
> >
> > On Fri, 26 Sep 2014, Martin Schreiber wrote:
> >
> >> On Friday 26 September 2014 10:38:36 Michael Van Canneyt wrote:
> >>>>
> >>>> Again have a look at MSEgui, tobjectlinker in mseclasses.pas. It is not
> >>>> so easy to implement as it seems. ;-)
> >>>
> >>>
> >>> It is. Depends on your definition of difficult, of course.
> >>>
> >> Or the implemented functionality.
> >
> >
> > Absolutely. A signaling mechanism, synchronous, is not hard.
> >
> > If you want asynchronous, or if you want the signal executed in the context of a thread in case of multiple threads, that is
> another matter.
> >
> > Although I am having difficulty seeing how you would decide which signal must be executed in what thread... an object does not
> automatically belong to a thread...
> 
> In Qt it does. Each QObject has a thread it is owned by and thus the signal handling mechanism knows to which thread to queue to
> deliver a signal to a certain object.

That is an implementation detail of Qt. Not so in FPC.

In each case, if the requirement is that it must work cross-process, then all processes need to use the same protocol.
So DBus is your best bet, since it is widely supported. I believe Qt uses it as well (or can use it).

Michael.