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

[Alan McKinnon]

On 03/06/2016 21:34, waltdnes@××××××××.org wrote:
> On Fri, Jun 03, 2016 at 10:35:45AM -0400, Ian Stakenvicius wrote
>
>> USE=gui is about building the graphical user interface that an
>> application offers, when it is optional.  That's it.  What
>> dependencies that means and so on have nothing to do with the flag.
>
>    That reasoning may have been valid many years ago when qt was the only
> toolkit around.  All GUI-optional apps back then either used qt or wrote
> their own primitives directly to X.  Fast-forward to 2016.  You now have
> X/Wayland/Mir/qt4/qt5/gtk2/gtk3/fltk/whatever.  If a package can have a
> GUI from more than one of the above, you *NEED* to select implementation
> type *SOMEWHERE* (make.conf/package.use/profile).  Deal with it.
>
>> You get that use flags are not supposed to represent dependencies
>> right, but features of the package??
>
>    Gentoo currently assumes that users are reasonably competent, and that
> if they've selected specific graphics libs to be linked to a package,
> that they've done it for a reason; i.e. to enable a GUI.

Walter,

I think you're missing where the devs want to take this and what USE is 
all about. It's about *features*, not about dependencies.

USE="gtk" is a dependency.
USE="gui" is a feature.
You only need enable a specific graphics lib flag when there is 
ambiguity about what "gui" means for a package.

>
>> Think about a wayland system -- there's lots of packages that
>> IUSE="X" to build their gui implementation.  If someone wanting
>> wayland set USE="-X" then they don't get the gui app even if it'll
>> work in wayland just fine.
>
>    If someone wants to run a wayland system, why wouldn't they set
> USE="-X -mir wayland" in make.conf in the first place?!?!?
>
>    Here's my problem with USE="gui"... I've set up various packages which
> have the gui/no-gui option.  If USE="-gui" overrides USE="X gtk3 qt4 fltk",
> then I would have to set USE="gui" *IN ADDITION TO* telling packages
> which GUI toolkit to use.  Since I may want some packages GUI, and some
> non-GUI, that would be one more USE flag to set in package.use and/or
> make.conf.
>
>    The reason for the pushback is that this "feature" would be rammed
> down peoples' throats, Poettering-style.  I propose a compromise
> solution that both sides should be happy with.  It would require 2 USE
> flags, namely "forcegui" and "forcenogui".
>
>    If "forcegui" is set, all optional-GUI apps will be built with GUIs,
> regardless of USE="-X -Mir -Wayland -gtk2 -gtk3 -qt4 -qt5".
>
>    If "forcenogui" is set, no optional-GUI apps will be built with GUIs,
> regardless of USE="X Mir Wayland gtk2 gtk3 qt4 qt5".
>
>    If USE="-forcegui -forcenogui" is set, things will be as they are
> today.  GUIs will be built, or not, depending on what toolkit flags are
> set or not set.  Gentoo is about choice.
>

That's a silly idea not least because it's non-deterministic. A force 
USE flag is really just USE="gtk" or USE="qt" on a larger scale as 
there's now *more* toolkits to randomly pick one from.

Most apps support one toolkit, often either gtk2/3 or qt4/5. It's a 
minority that support both and we have special means to handle those. 
For that small set of apps that do support several toolkits, what 
exactly are you going to force? If you can have one of gtk 2 or 3 but 
not both, which one is it? Well you'd need a USE="gtk2" or USE="gtk3" to 
find out what the user wants.

This proposal makes things simpler and reduces flags and their usage.
"gui" means build the gui the thing supports.
"X" stops meaning "gui" or maybe "XLibs" or perhaps "usually RDP but 
also supports magic X11" and starts to mean "X11 Window System" as 
opposed to Wayland or Mir.
The other toolkit flags start to mean specific versions of toolkits and 
only need be used when things get ambiguous and portage wants you you 
tell it what you want.

In short, flags will get simpler (as cruft will be removed) and flags 
gain clearer distinct names. Think of it as a code refactor after years 
of accumulating rubbish due to no clear plan.

Alan