Re: [Vala] Some basic problems with gstreamer

[Klaus Rotter <klaus rotters de>]

Phil Housley wrote:
> Normally you shouldn't need to cast a callback.  The issue here is
> that the function doesn't actually match the definition of SourceFunc,
> which takes no arguments in Vala.

The definition in the vapi file is:

public static uint add (uint interval, SourceFunc function);

Valac compiles this

        Timeout.add (200, (GLib.SourceFunc) printPosition);  

to that:

        g_timeout_add (((guint) 200), ((GSourceFunc) ogg_vala_printPosition), NULL);

I want instead of the NULL ptr a ptr to my pipeline class. So I changed
it to this

        ((Timeout) pipeline).add (200, (GLib.SourceFunc) printPosition);

valac compiles it to that:

        g_timeout_add (((guint) 200), ((GSourceFunc) ogg_vala_printPosition), NULL);

But I want this (in the c-code):

        g_timeout_add (((guint) 200), ((GSourceFunc) ogg_vala_printPosition), pipeline);

What's wrong? 

> Vala will use the data argument of a callback registering function to
> pass a "this" pointer, it's that which allows you to use an instance
> method as a callback.  If you run valac with the --save-temps argument
> you can see the C code that is produced, which is pretty useful for
> checking if you know a C API as well.

Hm... I think defining the callbacks inside the class (at least my way) 
isn't useful. I moved it outside (just like a global C function) and 
it worked better.

Isn't there a way to define the callbacks inside my class?

-Klaus