KWin's control over GTk3+ client-side decorations

[René J.V. Bertin]

On Monday May 25 2026 14:26:34 Kai Uwe Broulik wrote:

In fact, I was mistaken in my assumption that there was some "hacking" going on. GTk3 has builtin support for changing the window button layout, and all that kde-gtk-config does is synchronise the settings automatically.

That's different than what's going on with the window decorations themselves, which went from 4 flat (= shadowless) chunky, few-pixels-wide borders (basically a slimmed-down version of the old Motif window borders) to something a lot more subtle *with* shadows. The same look I get with GTk3/X11 applications under X11 with XFWM4 4.12 on Mac.
And that difference is purely linked to a KWin update from 5.15.5 to 5.18.5 , no changes in my gtk-3.0/settings.ini file needed.

R.

>that’s done by kde-gtk-config, see [1] and [2].
>
>Cheers
>Kai Uwe
>
>[1] 
>https://invent.kde.org/plasma/kde-gtk-config/-/blob/master/kded/gtkconfig.cpp?ref_type=heads#L255
>
>[2] 
>https://invent.kde.org/plasma/kde-gtk-config/-/blob/master/kded/configvalueprovider.cpp?ref_type=heads#L246