Re: [gtkmm] Concurrency with gtk/gtkmm

[Enrico Costanza <ec142 york ac uk>]

Many thanks for your reply.

I think I was not clear enough in my first email.

Tassos Bassoukos wrote:
> On Mon, 2002-11-11 at 20:57, Enrico Costanza wrote:
>
> [snip]
>
> > Up to now I have used idle function successfully to avoid GUI to freeze. 
> > I have tryed to use 2 idle functions hoping that this would simply and 
> > efficently put the two functions in parallel execution, but this does 
> > not work. One of the two is blocked. I have tryed a variety of values 
> > for the priority of the two (both 0, both a higher number, one lower and 
> > one higher value..).
> >
> > First of all I wander: why is this not working?
>
>
> Beacuse you are using two idle functions.
> You do not need to monitor the user interface, the main loop takes care
> of that for you atomatically. You just need to create and hook up your
> idle function, which should do some not too time-consuming processing.
> You then connect signal handlers to events, which (if that event is
> triggered) will be called between calls to your idle function. 

So, does that mean that only one idle function per time is allowed in gtk?



> As an example, say you have a process that goes on and on I (say,
> calculating the numbers of pi), and a button called "Stop". The button,
> when clicked, will set a variable named f.e. "stop_calculations".
> In the idle function, the code checks this variable, and if set will
> return "false" to remove itself as an idle handler. If not set, it will
> calculate the next digit of pi and return true, to remain as an idle
> handler..

That is ok, but my problem is that I need to monitor another (external) 
user interface (not gtk) and process some data at the same time.
I actually have (or wish to have) 3 things going on at the same: the gtk 
GUI, an external interface and a (sound) processing task.

I managed to have the first 2 running smootly, but I had lots of 
problems when I tried to add the 3rd one.



> > Also what should I then use to have 2 or more processes in parallel?
> > I have seen that glib supports threads, and I have also seen POSIX.
> > Is there any (dis)advantage in using one or the other with gtk/gtkmm?
> > (I have read that gtk is not thread safe, what does this mean in practice?)
>
>
> This means that you should not call Gtk+ (and therefore Gtkmm) code from
> two threads at the same time. You *can* have a thread for handling the
> UI and one (or more) for the other processing you need to do.
>
> Glib supprts threads and the associated infrastructure, but you will
> still need to create code that uses them.

Does that mean that Glib is not enough to have concurrency, but that I 
need (for example) Glib in addition to POSIX?


> > Is there any other option that i should consider?
> > (for this particular situation of monitoring an input, would it be worth 
> > to consider implmenting my own set of signals & handlers?)
>
>
> It depends on your timing constraints. Are 10 ms delays acceptable?
> 100ms?  100us?

My supposed bottleneck is at about 120ms, so this should be my target.
Thanks again,
Enrico Costanza