I need to do some actions before quit (save settings, etc.), I do it with Button widgets, but if I press on close button of the window, it just closes. Maybe I should handle App's on_close() event somehow? Then I don't know how to send data from Layout to App. For now I have smth like:
def quit_game(self):
# Saving different data.
...
quit()
What should I do?
Yes, you should handle the on_stop method on your App class by implementing the appropriate method.
Example:
class MyApp(App):
...
def on_stop(self):
# do what you need to here
value_to_save = self.root.subwidget.value
# self.root is your root widget - either the
# widget you return from App.build() or
# the root widget in your app kv file
Keep in mind, also, that if you plan to develop for Android you will need to implement on_pause as well. After an Android app is paused, it can be killed without warning by the OS and your on_stop method will not be called.