Union in Plasma 6.7

[Marco Martin]

I agree in setting it by default in the beta

On Mon, May 4, 2026 at 5:54 PM Nate Graham <nate at kde.org> wrote:
>
> I'd use plasma-integration to turn it on by default for Breeze QStyle
> users in the beta release; this kind of thing is what open betas are
> for, after all.
>
> To facilitate it, we should publish *extremely clear* information and
> instructions in the beta release announcement about what's going on,
> where to report bugs, and how to turn it off.
>
> Then I'd say we can evaluate based on feedback received during the beta
> whether to keep it on for the general release of Plasma 6.7.
>
> Nate
>
>
>
>
> On 5/1/26 4:42 AM, Arjen Hiemstra wrote:
> > Hi,
> >
> > With Plasma 6.7 we will have a release of Union, the new style engine that
> > we've been working on for a while now. The current state is that we have a
> > fully implemented QtQuick Controls style along with a Breeze reimplementation
> > in CSS. Some of us have been daily driving it for a while now and while there
> > are regressions, most of these are to the extent of slightly different paddings
> > or mismatching colors.
> >
> > However, we cannot test all applications out there on our own, so we may have
> > missed things. We really need more testing to figure out if there is major
> > breakage and if so, how things break.
> >
> > This isn't really possible without a more general rollout of Union, so we had
> > some discussion yesterday about what exactly we want to do for 6.7. I think
> > there have been three options floated about:
> >
> > - We switch the default QtQuick Controls style. Since only Breeze is currently
> > implemented in Union, switching it without some fallback would annoy people
> > who don't use Breeze QtWidgets, so the current idea is to only use it when the
> > user has selected Breeze. The main drawback is that there's no simple escape
> > hatch for if an application does break to such and extent that it is unusable.
> >
> > - We add an option somewhere for users to opt in using Union. The advantage is
> > that this could be fully opt-in. It could also explain more about what it is
> > and what the state of things is in UI. The disadvantage is that for most users
> > it is going to be a meaningless option that they won't fully know what the
> > implications are, since it's mainly a technical option.
> >
> > - We do not do anything and rely on users setting `QT_QUICK_CONTROLS_STYLE` to
> > Union. This I think is the worst outcome, as it makes it quite unlikely that
> > many people use it, which means we don't get the testing coverage for Union
> > that we need at this point.
> >
> > I know this discussion should have been started sooner, but the soft freeze
> > date kinda snuck up on me, so here we are.
> >
> > - Arjen
> >
> >
>