Re: enums that are really just sets of constants

[Kjell Ahlstedt <kjellahlstedt gmail com>]

Den 2017-05-06 kl. 23:09, skrev Jonathan Wakely:

On 6 May 2017 at 21:00, Murray Cumming <murrayc murrayc com> wrote:

The old style-enum won't let us change this, in gtkmm 3,

Gtk::RESPONSE_OK
into this, in gtkmm 4:
Gtk::Dialog::Response::OK
without also polluting the API with this
Gtk::Dialog::OK

Using an old-style enum would let us have this:
Gtk::Dialog::RESPONSE_OK,
(and Gtk::Dialog::Response::RESPONSE_OK)
which is still an improvement, but not quite as nice.

Strictly speaking, an old-style enum *and* a scope would allow that.

namespace Gtk {
  struct Dialog {
    struct Response {
      enum ResponseEnum { OK };
    };
  };
}

That would give you the implicit conversions of old-style enums, but
still give scoped names. That might not be useful, I'm just saying
it's possible.
_______________________________________________

That might very well be useful. A minor drawback is that we would have both Gtk::Dialog::Response::OK (wanted) and Gtk::Dialog::Response::ResponseEnum::OK (unwanted). With an unnamed old-style enum there would be only Gtk::Dialog::Response::OK.

namespace Gtk {
  class Dialog : public ... {
  public:
    struct Response {
      enum { OK };
    };
  };
}

An unnamed enum entails some restrictions, as discussed in https://bugzilla.gnome.org/show_bug.cgi?id=86864#c34, but that's probably not important for the very few enums in gtkmm and other mm-modules where we want implicit conversion to int.