Wrong or missing halo/shadow around undecorated windows?

Help
1

I’m stumbling a bit with Firefox on a dark mode + dark background. I’m using the Kubuntu Dark theme + Oxygen decorations/style. Firefox is nicely un-decorated, using the built-in FF decorations. The one issue:

For every other application, the active window has a glowing cyan halo around it, helping it to pop against the dark background. Except for Firefox. Firefox’s window has a black drop-shadow halo around it, even when it’s active. Is there a way to get just the active-window halo decoration onto FF?

Contrast:

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image1091×681 99.1 KB

vs

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image1092×671 72.4 KB

Also I just noticed the same problem exists for VSCode, but even worse it lacks even the drop shadow black halo, it’s just a hard edge.

I’m using KDE Plasma in Kubuntu 26.04 LTS. I love Plasma (and put a lot of effort into unscrewing my system when I tried to install LXQt onto the same system).

Little help? Thanks.

2

This is because the glow is part of the system-decoration and therefore not included in the built-in decoration of Firefox or VS Code. You could try to use window-rules to force the system-decoration on those windows.

3

But then you get a redundant titlebar. Is there any way to only apply the glow and not the titlebar? I can’t even figure out if Firefox’s drop-shadow is coming from Oxygen (which draws a similar drop-shadow on certain dialog-like windows (although they aren’t classed as dialogs - eg dialog windows of GIMP get the drop shadow) or it’s coming from Firefox itself.

4

No, at least not at the moment.

We’re working on shadow-only decoration support, which I believe would apply the glow, too. But it’s not ready yet.

5

Maybe this could fix this in the future. Server-side Drop Shadows – Vlad Zahorodnii's Blog