Re: [gentoo-dev] [RFC] Global USE=gui

[Brian Dolbec]

On Tue, 7 Jun 2016 14:29:58 -0400
Michael Orlitzky <mjo@g.o> wrote:

> On 06/07/2016 12:20 PM, Michał Górny wrote:
> >
> > So many weird ideas... while the simplest one is a proper
> > REQUIRED_USE with gui being the control flag, and IUSE defaults to
> > select the preferred toolkit.
> >
>
> This is what came to my mind.
>
> The underlying problem that we are hitting (a la Patrick) is that USE
> flags are supposed to be a user-interface for building software from
> source, but implementation details are an important part of
> configuring the software to be built.
>
> It would be nice if USE=gui meant "build a GUI" and that was all the
> input that we needed from the user. But if the upstream package
> supports both QT and GTK and we need to pass either --with-qt or
> --with-gtk to the build system, then there is an unavoidable choice
> to be made. We can prefer one, but both options need to be available.
>
> If we want the best of both worlds -- a nice user-interface and full
> configurability -- then we can use "the user wants a GUI" as a trigger
> for the implementation choice. If there's a default implementation and
> the user doesn't care, no further interference should be necessary.
> Otherwise the presence of the generic USE=gui will let us know, so we
> can let the user know, that he needs to pick one.
>
>

This is where my thought from a few days ago kicks in...
I had started to discuss it with Kristian.


I propose to help alleviate the __MESS__ from all this force-foo and
other complicated USE flag REQUIRED_USE madness...

We instead implement something along the lines of:

an ordered list of the gui toolkits in their preferred order of
desirability.  This should be an all inclusive list.  Note: these are
subject to package.use setting overrides.

PREFERRED_GUIS="gtk2 qt4 qt5 x wxwidgets X ... ncurses tty -gkt3"

In the above it means that if gtk2 is an option, then choose it, mask
(de-select) the others.
In there it also means DO NOT SELECT gtk3!!!!  So if you want a pkg and
it NEEDS gtk3, then the PM will puke it back at you saying you can't
have one without the other...
So, then you have to fix it manually via package.use settings.  Accept
gtk3 for this pkg only (not that it doesn't likely have other gtk3
deps that will also need this...)

In the general case it will pick the first toolkit in order of
preference (left to right) and only that toolkit that the pkg is capable
of using.

For pkgs capable of multiple simultaneous toolkits installed, then
again, manual intervention would be needed to set package.use.

This would also have to be a package manager feature and run similar to
the auto-unmask feature.

FEATURES="preferred-guis"

Let's try and keep things as simple as possible.
From what I've gleaned form the emails I have read, is that what the
general user wants to happen, select the toolkit in the order of their
preference.
-- 
Brian Dolbec <dolsen>