Re: [Vala] Some basic problems with gstreamer

["Phil Housley" <undeconstructed gmail com>]

2008/4/22 Klaus Rotter <klaus rotters de>:
> Klaus Rotter schrieb:
>
> > /home/klaus/oggtest/oggtest.vala:65.17-65.27: error: Argument 2: Cannot
>  > convert from `oggVala.printPosition' to `GLib.SourceFunc'
>  > Compilation failed: 1 error(s), 0 warning(s)
>
>  Ah... shame on me! A type cast did the trick. I thought in those
>  high-level programming languages you don't need those constructs :-)
>
>  >                 Timeout.add (200, (Glib.SourceFunc) printPosition);

...

>  But it seems I cannot give an argument to Timeout.add like I could do in
>  C g_timeout_add. Is there any reason why all member in class Timeout in
>  glib-2.vapi have no data argument? Or is this an error?

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.

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.

Did that make sense?  I''m not sure now...
-- 
Phil Housley