> PS: Apparently you are overloading the word "display" to mean both "show" and "hide". Both for the function called performDisplay() and the event called delite-display-before (and perhaps another one). It seems like you should have separate events and functions for hide vs. show, or at a minimum, less confusing names.

Yes that's exactly it. The idea was to get a single function (on or off) of the child. Basically performDisplay is performing the display type that is asked to it (either true or false) "just" like display CSS property allows to display "on" (inline, ...) or "off" (none).

As these are not tasks (calling performDisplay, listening to before event) that are usually performed by the application developer (he does not call those methods himself but call show and hide which are indeed differentiated) it sounded as simple to not duplicate them as people interested in this (controllers etc...) don't care about the difference, they want to be notified in similar manner whether this is a hide or show, in the same area of their code. Having two of them would actually make things more complicated for those who are the target for that (basically they would probably have to implement the two method but then delegate most of the code to a single one).

That said if you have a better name suggestion I'm all ready to hear it, you probably have a better sense of English words than I have! I'll keep thinking about a better name of my side meanwhile.