Re: [Vala] GStreamer Gst.Pad

[John - <arenal85 hotmail com>]

I try with :

Pad.add_buffer_probe(this.test_buffer);

    public bool test_buffer (Pad pad, Buffer buffer) {}

And I get :
expected ‘GCallback’ but argument is of type ‘gboolean (*)(struct GstPad *, struct GstBuffer *, void *)’]

> > Hi,
> >
> > I am doing some test with GStreamer and Vala.
> >
> > In other program language, i usually use Gst.Pad.add_buffer_probe method but in Vala i don't know how to 
> > use it.
> >
> > I try to do :
> >
> > Pad.add_buffer_probe.connect(test_buffer()); 
>
> That is syntax for signals. This is not a signal, but a method taking
> a callback.
>
> > And also i try :
> >
> > Pad.add_buffer_probe(test_buffer()); 
>
> It wants a callback, so you must pass a function, not result of one. So
> something like
>
>     Pad.add_buffer_probe(this.test_buffer);
>
> or, if it's a method of different object, it might be
>
>     Pad.add_buffer_probe(instance.test_buffer);
>
> Where the test_buffer method must be declared to match the
> BufferProbeCallback, so like
>
>     bool test_buffer (Gst.Pad pad, Gst.Buffer buffer) { ... }
>
> Doing it as instance method is recommended -- the instance is what is passed
> via the user_data you normally have in C.
>
> Most recent vala also supports closures, so you could than also use
>
>    Pad.add_buffer_probe((pad, buffer) => boolean-expression);
>
> or
>
>    Pad.add_buffer_probe((pad, buffer) => { test-code; return result; });
>
> The syntax is supported for long time already, but only since valac 0.7.6 you
> can refer to variables of enclosing scope there and you may still encounter
> some problems with that in 0.7.6. Jürg already talked about releasing 0.7.7
> yesterday, so it should be in a day or two. Closures should be well usable
> there.
>
> -- 
>                                                Jan 'Bulb' Hudec 
                                          
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