[Development] QML: Why C++11 scoped enums are not scoped in QML?

[BogDan Vatra]

On joi, 28 iulie 2016 09:52:56 EEST Dominik Holland wrote:
> Am 28.07.16 um 09:41 schrieb Olivier Goffart:
> > On Donnerstag, 28. Juli 2016 10:32:54 CEST BogDan Vatra wrote:
> >> On miercuri, 27 iulie 2016 09:08:32 EEST Thiago Macieira wrote:
> >>> On quarta-feira, 27 de julho de 2016 11:47:03 PDT BogDan Vatra wrote:
> >>>> On miercuri, 27 iulie 2016 10:35:01 EEST André Somers wrote:
> >>>>> Op 27/07/2016 om 09:53 schreef BogDan Vatra:
> >>>>> Would that not break existing QML applications that now use enums
> >>>>> backed
> >>>>> by scoped enums in C++?
> >>>> 
> >>>> It will, but personaly I can't see a better solution ...
> >>> 
> >>> I have already said what to do: make it an opt-in on registration of the
> >>> enum to the QML/JS engine.
> >> 
> >> Got it  :)
> >> 
> >>>> So, either we break the existing QML apps that used scoped enums in C++
> >>>> (which is useless, because in QML side you'll get name clashing) or we
> >>>> keep
> >>>> it as it is now and never "fix" it. I'd like the first option :).
> >>> 
> >>> I really hate it. Breaking applications should not even be an option on
> >>> the
> >>> table. Let's start with "we won't gratuitously break applications" and
> >>> work
> >>> to find a solution from there.
> >>> 
> >>>> Of course if we can find a better solution to have them both is even
> >>>> better
> >>>> !
> >> 
> >> What I was trying to say here is that I'd like to have by default C++11
> >> scoped enums scoped also on QML, but if everybody thinks is a no go, than
> >> we can co the other way around.
> >> 
> >> Anyway, I checked the code a little bit, hopping it will be a few lines
> >> change, but I was so wrong :). I tried to prefix the (scoped) enum keys
> >> with the "EnumName." but of course it didn't worked :D, "EnumName_"
> >> works fine. It seems it needs much love (probably some virtual types
> >> based on
> >> EnumName), unfortunately my QML engine knowledge are too limited to
> >> continue :).
> > 
> > Note that in C++11, all enums can be used scoped. (even the normal ones)
> > I think it would make sens to allow all enum to be used scoped in QML too.
> 
> Mhh how do you make sure that the Enum names are unique ? E.g. having
> two custom Items and both having a Enum in them called Type, what whould
> you get if you do Type.FOO ?
> 
Nothing, C++11 scoped enums just add one more scope of their existing scope. 
So, if you have:
class Type {
enum class Enum {
  FOO
}
};

In C++ you'll need to use *Type.Enum.FOO* to access it, and we want to have 
the *same thing* in QML :).

[...]

Cheers,
BogDan.