[GUI] Re: GUIs and events/callbacks

[George Russell]

Glynn wrote (snipped)

> Does this mechanism allow the toolkit to determine whether an event is
> being listened for? Or would it force the toolkit to always generate
> all events just in case it's being listened for? The latter is
> unacceptable on X.

Yes.  You'll see I provided an IO *action*

    clicked :: Clickable widget => widget -> IO (Event ())

This tells the toolkit to *generate* an event whenever a button (or
whatever "widget" is) is clicked.

I agree that the alternative, for general GUI events, would be unacceptable.