Union in Plasma 6.7

[Paul Brown]

On Friday, 1 May 2026 12:42:23 Central European Summer Time 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.

Hi Arjen,

Maybe if we can have some clear step-by-step instructions with illustration 
in, say, a blog post, that includes how to acquire and report bugs,  we can 
push it to social media and get you the tester you need.

Cheers

Paul
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