Thanks, some helpful comments and I will inlcude them.

Gtk3 is very like gtk2, but my experience is that you can rarely just change gtk2 to gtk3 and expect it to work. Small changes that are minor issues for veteran coders become complete major roadblocks for beginners.

The tutorial was really aimed at beginners, particularly my 15 year old son and his friends. I included "use diagnostics" to give new users some more feedback, although I often find it more verbose than helpful myself.

I am debating about whether to include complete programs in tutorial. On the downside it makes it repetitive and excessively long; on the plus side everything is in one place. I think at this stage I will continue getting the examples written and base text down and ponder the formatting a little longer.

I will include an example of passing an array ref back as $userdata and include examples avoiding using globals when not necessary.