Re: Template Widgets inside another GtkBuilder file

[Tristan Van Berkom <tristan upstairslabs com>]

On Sat, Oct 3, 2015 at 10:14 AM, Victor Aurélio Santos 
<victoraur santos gmail com> wrote:
> How can I do that ?
> Just build all together results in this warning:
>
> >  (ajami:3475): Gtk-CRITICAL **: Error building template class 
> > 'AjamiMainWindow' for an instance of type 'AjamiMainWindow': Invalid 
> > object type 'HVMeter' on line 2
>
> I've asked on SO[1] and got only one answer.
>
> I stick at "_get_type" workaround/hack but I didn't like it and I
> can't do the same thing in Vala (I've not found how to do the same
> thing).


Hello Victor,

The regular way to do this is in fact to compile your app with 
gmodule-export-2.0.pc

I.e. adding `pkg-config --libs gmodule-export-2.0` to your link stage 
(using autotools you
would just add gmodule-export-2.0 to your regular pkg-config m4 macro 
invocations).

This indeed makes your applications global symbols visible so that they 
can be found using dlsym() on unices and other methods on other 
platforms.

Regarding the comment on the SO post, the deriving of the _get_type() 
function by the type name is not considered a heuristic but rather it 
is a standard, which is at least enforced in any code written in the 
last decade or so by way of the G_DEFINE_TYPE() macros (vala generated 
types will also comply with this standard). So, if you have a type 
which is named FooBar, and it's low level GType accessor is not 
correctly named foo_bar_get_type(), it is in fact the 
application/library code declaring the type which is at fault for not 
complying with this.

Granted, one can argument that documentation in this area is weak. Any 
other methods provided in GtkBuilder (such as overridable 
get_type_from_name() virtual methods) are specifically targeted at 
language bindings which need to resolve the type in other ways.

With all that said, it could be plausible to create some tooling 
perhaps which parses your builder files at compile time, perhaps 
generating a resource to be compiled into your app which could be 
automatically inspected at gtk_init() time, to automate the process of 
initializing the required types - and removing the requirement of 
exporting your symbols in the regular way - that's one approach I can 
imagine anyway, perhaps there are others, there would have to be 
interest and someone would of course have to write that code :)

I hope this clarifies the situation a bit more for you.

Best,
   -Tristan