Auto-Hide Panel: activation strip flickers constantly

Distribution

Linux Mint 22.1

Package version

6.4.8

Graphics hardware in use

Intel Corporation UHD Graphics 620 (dual-gpu system, but dGPU is completely off via my computer's UEFI settings)

Frequency

Always

Bug description

I recently changed my theme from Mint-Y-Orange to Mint-X-Purple. I previously used Mint-Y-Dark-Orange for the desktop and panel theme, and changed it to also be Mint-X-Purple.

I have a single panel at the top of my screen, and a plank dock on the right that also auto-hides. I notice the little line that is there to tell you a panel is there, the activation strip, flickers. This is very noticeable with a dark bg color set for the desktop wallpaper.

But if I look closely with a window maximized, I can see the flickering constantly. This is distracting. I can see it even with it in my periphery.

Testing with other themes, Mint-Y-Dark-Purple is really difficult to discern whether or not it flickers. I think it does. Mint-Y-Purple (light panel themes) does as well. The Mint-X themes seem to flicker more severely, but they both flicker.

Steps to reproduce

Auto-Hide Panel:

1. Go to "System Settings" -> "Panel"

2. Set "Panel Visibility" to "Auto hide panel"

Switch to a light theme:

1. Go to "System Settings" -> "Themes"

2. Click "Advanced Settings" (if not already using them)

3. Change your desktop theme to any light theme.

Change Wallpaper (for better visibility of the issue):

1. Right-click your desktop background and left-click "Change Desktop Background"

2. Pick any picture with dark colors, or click "Settings" in the same Window and set your background color to solid black.

Expected behavior

The activation strip doesn't flicker.

Additional information

Disabling all my 3rd-party applets and desklets doesn't change the behavior. But just in case, they are the following:

Desklet:

Google Calender by slgobinath

Applets:

Better Backgrounds by simonmicro
KDE Connect Control Center by Severga
Night Light Switch by claudiux
Weather by Gr3q

inxi -Fz.txt

xsession-errors-scrubbed.txt.gz

Reproduce the flicker through System Settings → Panel by enabling Auto hide panel, then switch to a light theme and use a dark wallpaper for visibility. Compare the activation strip across the listed themes and with third-party applets and desklets disabled. Done means the activation strip remains stable instead of flickering.