gtk introduction tutorial and builder

[Michael Vetter <jubalh iodoru org>]

Hello,

as a Newcomer I started to follow this guide:
https://developer.gnome.org/gtk3/stable/ch01s04.html#id-1.2.3.12.5

Which I think is very good.
I chose gnome-builder in favour of vim to have a better gnomeish
experience.

When one starts a default project in Builder the application is
slightly differntly organized than in above mentioned tutorial. Which
on some occasions creates problems for me since I'm not yet able to
understand what exactly is different and how to apply the tutorials
code to fit with Builders default code.

I assume that the Tutorial uses a simpler way of constructing the
application and that Builders is a bit more future-proof for an
application that will get more extended.

Would it be possible if somebody knowledgeable enough could update the
tutorial to be more based on Builders default project?

I struggle already with things like fitting `G_APPLICATION_CLASS
(class)->open = example_app_open;` in there.

Best,
Michael