Access to private EventHandlers

José Pereda jose.pereda at
Thu Dec 17 18:57:26 UTC 2020

While chasing down an issue on Mac with application events, we have noticed
that there is some code under a private package that apparently it is
supposed to be used by developers, which of course it is discouraged: [1] is a public static inner
class under a private package, that is added to the Application class for

So far, only QuantumToolkit does subclass it [2] (just for Quit action and
Theme changed events). However the EventHandler class has more methods for
listening to MacOS/iOS application events.

While most of those events happen before the app starts (and it wouldn't
make sense to try to listen to them app-wise), in particular, the
OpenFilesAction event is forwarded [3] when a second EventHandler is set.
Other events like resign/become active actions can be listened to as well.

A developer could provide a subclass of such EventHandler if it were public
API, but so far, that has to be done accessing private API.

At this point, and following on this other thread [4] that discussed a
similar issue with EventHandlerManager, we should start considering the
design of new public API that could provide developers with access to such
events, with considerations to possible platform specifics.




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