Re: [gentoo-dev] [RFC] Useflags: qt, qt3, qt4?

[Donnie Berkholz]

Kevin F. Quinn wrote:
> On Tue, 20 Jun 2006 16:14:08 -0700
> Donnie Berkholz <spyderous@g.o> wrote:
>
>> Mike Owen wrote:
>>> From this user's perspective, simple is better. qt3 and qt4 as use
>>> flags are completely and utterly obvious as to what they mean, and
>>> there is no confusion about them. Adding a plain qt flag in there
>>> brings back the gtk/gtk2 mess that we've presumably been trying to
>>> avoid in the future.
>> That depends on how it's done. If it's done in a simple and obvious
>> way (USE=qt means use the best available qt, USE=qt# for other weird
>
> where "available" means "available in the tree for arch", not
> "already installed on build system" (just to be clear - correct me if
> I'm wrong)

Yes, but it's more than that.

Available will vary on a package-by-package basis. Package "A" may have
qt4 and qt3 available, package "B" only qt4, package "C" only qt3.

USE=qt would use qt4 on A, qt4 on B, qt3 on C.
USE=qt3 would only affect A.

>> stuff that most people don't care about and so can ignore), it
>> shouldn't be that bad.
>
> So are you suggesting something like:
>
> qt - Add support for QT/include QT GUI
> qt3 - build for version 3 of QT
>
> where dependencies might be something like:
>
> qt? ( qt3? ( >=dev-libs/qt-3.3.6
>              <dev-libs/qt-4 )
>       !qt3? ( >= dev-libs/qt-4.1 ) )

Well, I'm not sure of the best behavior. If they have USE="qt qt3",
they're saying they want both the best available qt and qt3. I'd suggest
the natural preference would be best available _over_ qt3, in cases
where both are available and mutually exclusive.

So more like:

qt? ( =qt-4* )
!qt? ( qt3? ( =qt-3* ) )

Your inital dep string may not do what you intend, though. Something
more like

=qt-3*
=qt-4* for the two sections

> for a package that can build against either qt3 (3.3.6 or higher) or
> qt4 (4.1 or higher) but not both simultaneously, and perhaps:
>
> qt? ( >= dev-libs/qt-4.1
>       qt3? ( >=dev-libs/qt-3.3.6
>              <dev-libs/qt-4 ) )
>
> for packages that can build simultaneously for both (is this situation
> realistic?).

Yes, e.g. poppler-bindings

> We'd need a qt4 to get just the qt3 package in that case:
>
> qt? ( qt4? ( >= dev-libs/qt-4.1 )
>       qt3? ( >=dev-libs/qt-3.3.6
>              <dev-libs/qt-4 ) )

No, this isn't right. The qt flag is only controlling whether the "best"
interface is built, has nothing to do with older interfaces.

qt? ( =qt-4* )
qt3? ( =qt-3* )

The goal is to avoid a double-flag combo to do a single thing. "qt"
always and only affects the _best_ available qt interface for that
package. "qt#" affects only _older_ available qt interfaces for that
package.

> Am I making sense?  This looks a lot like the gtk/gtk2 flags, but
> inverted; according to use.desc, gtk builds gtk+-1 unless gtk2 is set,
> whereas the above builds highest version compatible with the
> package unless a lower version is specifically requested through USE.
>
> Ideally we should be consistent in handling this issue (which
> presumably isn't limited to just gtk and qt), although it may not be
> worth the disruption to rework gtk/gtk2 into gtk/gtk1.

Thanks,
Donnie