`OO.ui.mixin.LookupElement` should have an option to only show suggestions after the user pressed a key, and not just on focus. This is different from the current `allowSuggestionsWhenEmpty` option, as the input might have some pre-filled value. Even then I would like to show suggestions not when the user focuses the input, but only once he typed in some additional text.
The place I want to use this is https://de.wikipedia.org/wiki/Benutzer:Schnark/js/veSummary.js, which provides suggestions for the edit summary in VE. It should mimic the usual browser behavior for autocompleting forms, which is as described: You don't get suggestions directly after focusing, but only once you interacted with the input.
Currently I just override the `onLookupInputFocus` method to suppress showing the suggestions there, but as this method officially is protected, this certainly is not the best way to do it.