[Feature Request] Expose methods to C, to be called from signals

[BigBoyBarney]

Hi!

It's possible to bind a button, or any other property for that matter via expressions, to a function in C. Relevant blueprint documentation for signals and closure expressions.

Button {
  clicked => $on_button_clicked();
}

This would allow us to replace

button.clicked_signal.connect(->on_button_clicked)

and use closure expressions in blueprints (very useful)!

I have 0 idea whether this is feasible at all, but an annotation like for properties would be amazing

class Snorlax
  @[GObject::Property]
  property size : Int32

Cheers, and happy new year!

[hugopl]

I had a branch somewhere with some small fixes to be able to use Gtk expressions, I stop working on it because I noticed that I would not need GTK expressions for what I was doing.

IIRC I had to add a finalizer for GTK::Expression so gi-crystal calls the right destruction function and not crash.