[Vala] Best way to handle errors in a GUI application?

[Steven Oliver <oliver steven gmail com>]

After getting some great help after my last post, I have run into another
issue I'm not sure how to solve. How do people recommend you handle errors
when making a GUI application? I planned on taking the obvious approach of
a pop-up message dialog that tells the user what they've done wrong, or
what went wrong, but that has turned out to not be quite so easy. My code
is architected such that the Application class creates the Main Window
object which in turn creates a Gtk.Box object. So if the error occurs in
the Box object, how do I create a message dialog tied to the main window?
Do I have to pass the main window object around? Or is there a better way
to do this that I'm missing?

My code is here if my explanation didn't make sense:
https://github.com/steveno/balistica

Again thanks for all the help!

Steven N. Oliver