[Vala] Question about vapi and CCode attributes

[Tomasz Jankowski <tomcioj gmail com>]

Hello!

II'm working on GTK+ based application and I decided to use Vala to make my
life easier. I was wrong (partly)...

I design windows in Glade and then load created XML files GTK+ Builder.
According to samples at Vala's homepage I added additional attributes to my
code to used callbacks autoconnect:

[CCode (instance_pos = -1)]

public void on_about_menu_item_activate (Gtk.MenuItem menu_item)
{
    AboutDialog dialog = new AboutDialog ();

    dialog.display ();
}

Later I decided to add internationalization support and because I use
Autotools I looked how it's done in http://github.com/tadeboro/Sampala . My
config.vapi:

[CCode (prefix = "", lower_case_cprefix = "", cheader_filename =
"config.h")]


namespace Foo
{

/* Package information */

public const string PACKAGE_NAME;

public const string PACKAGE_STRING;

public const string PACKAGE_VERSION;


 /* Gettext package */

public const string GETTEXT_PACKAGE;

 /* Configured paths - these variables are not present in config.h, they are

* passed to underlying C code as cmd line macros. */

public const string LOCALEDIR;  /* /usr/local/share/locale  */

public const string PKGDATADIR; /* /usr/local/share/sampala */

}

I also added flags: "--vapidir=. --pkg=config" to Vala compiler (config.vapi
is placed in the same directory that source code files are) and flags to
GCC: -include
$(top_srcdir)/config.h -DLOCALEDIR=\""$(localedir)"\"
-DPKGDATADIR=\""$(datadir)"\"

When I added config.vapi to my project it broke callbacks autoconnect (but
localization works fine), runtime errors:

(foo-gtk:24482): Gtk-WARNING **: Could not find signal handler
'foo_on_quit_menu_item_activate'

(foo-gtk:24482): Gtk-WARNING **: Could not find signal
handler foo_on_about_menu_item_activate'

etc.


I stared reading Vala documentation, searching web and finally I figured
out, that this construction works fine for me:

[CCode (instance_pos = -1, cname = "foo_on_about_menu_item_activate")]
public void on_about_menu_item_activate (Gtk.MenuItem menu_item)
{
    AboutDialog dialog = new AboutDialog ();

    dialog.display ();
}


Questions:

   1. Why config.vapi addition broke callbacks autoconnecting?
   2. Is there any other way to achieve the same result
   without writing cname attribute for each callback?
   3. What does instance_pos attribute?