appearance setting view shows thick border

[Carlo Lobrano]

Appearance setting seems to have a double border in the separation from the sidebar

steps to reproduce
1. open gnome-control-center
2. click on appearance tab
3. compare the border-from-sidebar with another setting page

lsb_release -rd
Description: Ubuntu Focal Fossa (development branch)
Release: 20.04

$ apt-cache policy gnome-control-center
gnome-control-center:
  Installed: 1:3.35.91-0ubuntu2
  Candidate: 1:3.35.91-0ubuntu2
  Version table:
 *** 1:3.35.91-0ubuntu2 500
        500 http://it.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gnome-control-center 1:3.35.91-0ubuntu2
ProcVersionSignature: Ubuntu 5.4.0-14.17-generic 5.4.18
Uname: Linux 5.4.0-14-generic x86_64
ApportVersion: 2.20.11-0ubuntu18
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Tue Mar 3 13:28:14 2020
InstallationDate: Installed on 2020-03-03 (0 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20200220)
SourcePackage: gnome-control-center
UpgradeStatus: No upgrade log present (probably fresh install)

[Robert Ancell (robert-ancell)]

This is because the setting tab has keyboard focus - it's the same for all the tabs. If you change focus, e.g. on appearance select the the "Position on Screen" combo box then the border goes away.

Is this just the way it is rendered in GTK/the theme?