[gtkmm] Re: How to do call a function once every 'frame'? And some documentation feedback.

[Dirk Gerrits <dirk gerrits homeip net>]

Bassoukos Tassos wrote:

> On Sat, 2002-11-09 at 15:29, Dirk Gerrits wrote:
>
> >Hi,
> >
> >I'm trying to find out how to have a function called once every 'frame'.
> >In a Win32 program that would mean something like:
> >
> >while (!quit)
> >{
> >     // Win32 event handling here
> >     // ...
> >
> >     DoFrame();
> >}
> >
> >How would I do this in gtkmm2?
>
>
> If you want to do a long-running computation whithout threads and
> without blocking the user interface, use
>   Glib::signal_idle().connect(slot_to_run,priority);
> Where slot_to_run is the slot you want to call when your program will
> start to become idle and priority defines the priority at which the 
> idle state will be cheked (see [1] if this does not make any sense).
> Your slot should not take too long to finish though, so that 
> computation and event processing can be interleaved.
>
> If instead you want to do some computation every N miliseconds, use
>   Glib::signal_timeout().connect(slot_to_run,N,priority);

I need the latter. Thanks a lot.

> In both cases, priority has a sane default value.
>
> [snip -- some very relevant documentation questions]
>
> >All of these questions remain (largely) unanswered. It seems the
> >reference documentation can use a lot of improvement. There's a lot of
> >missing documentation and also a lot of plain stupid documentation. Here
> >is one example that shows the latter:
> >
> >SignalIdle Glib::MainContext::signal_idle()
> >
> >Idle signal, attached to this MainContext.
> >
> >Returns:
> >     A signal proxy; you want to use SignalIdle::connect().
> >
> >
> >This little piece of documentation tells you ABSOLUTELY NOTHING that the
> >function signature doesn't tell you. I don't want to know that
>
>
> It does: it returns a *signal proxy* (see the Proxy pattern), that 
> mean that it is only an intermediary, and right afterwards: "you want 
> to use SignalIdle::connect()", where you should go and read the docs now. 

Yeah I realize that now. I think it should read "For more information 
see: SignalIdle::connect()" instead of "you want to use 
SignalIdle::connect()" though.

> >signal_idle stands for the idle signal, I want to know WHAT an idle
> >signal is and WHEN it is called. The documentation for
> >Gtk::Main::signal_quit is much better for example.
>
>
> The documentation for SignalIdle::connect states that the splot
> parameter is "A slot to call when the main loop is idle". Idle as in
> "the program has nothing more to do and will sleep for an event".

How about adding a section on definitions to the reference 
documentation? Your explanation of 'idle' seems like a great candidate 
for that. And there are most likely a lot more terms that could benifit 
from a central place where they are explained. Thread, process, signal, 
slot, etc, etc. Just an idea though.

> >The tutorial is very good IMHO, but it does not tell you everything.
> >That's what the reference documentation is supposed to do, right?
>
>
> >So can anyone who knows gtkmm2 well enough that he doesn't need the
> >reference tell me how I would accomplish my once every 'frame' function?
>
>
> It would help if you defined better wht a frame is.

Yeah sorry about that. I explained it in detail in my answer to Leslie 
Polzer's reply.

Dirk

> [1] the priority levels are there to distinguish between the
>     different sources. In this context, idle meand that only
>     lower-priority sources (if at all) want to do something.