Let's start with enhancing the small app from the last step.

The problem that we are facing right now is, if we close the app through the window-managers 'close' button, the application (or better the GTK-Main-Loop) is still running and to end it, we have to press Ctrl-D.

Because I start the script from the command-line, I also would like to see, if I close the app, that the command line will come up again.

The solution seems, to create a method, that would be called, if the user presses the close button. We have to clean up the window and to close the app.

This seems implemented in GTK in 2 callbacks, the delete-callback for closing the window stuff and the destroy-callback for exiting the application (or the GTK-Main-Loop).

Therefore, I enhanced the initialize method from the last example with 2 lines of code:

window connectSignal: 'destroy' to: self selector: #destroy:data: userData: nil.
window connectSignal: 'delete_event' to: self selector: #delete:event:data: userData: nil.

There we call the method connectSignal for window with the identfier "destroy" (or delete_event) and say that the current object (self) is responsible for handling this callback. This callback should be routed to the method #destroy (or #delete) and has the parameters : and data:. (Currently, I have no Idea, what the userData is for, I found only a connectSignal method in the GTK.GObject defined and this method has no parameter userData...)

We also have to define the callback-methods, that the callbacks don't run into nirvana:

destroy: object data: data [
     GTK.Gtk mainQuit
]

delete: object event: event data: data [
     window destroy
]

And here you see again, the delete event is for closing the window and the destroy event for leaving the Gtk-endless-loop which was entered with the code-line GTK.Gtk main at the end of the MainWindow.st source-file.

For the main-window of an application, I think only the destroy-callback is neccessary. I would assume, that the delete-callback comes into play, if we work with additional dialogs, but that we will see later on in the future...

Important:
|-
|a lot of the example-code used here, can be found in the source-directory from gnu-smalltalk in the packages/gtk directory in the example_*.st files.

Sourcecode used in this examples:

Joachim.