Strange visual effects in many programs if display is zoomed

hello KDE forum, i wonder if you can help me out. i have these strange visual effects on most applications, such as konsole, yakuake, firefox, mpv and discord. they appear in windowed, maximized and fullscreen modes. the issue seems to disappear when zoom is set to 100%; it appears at both 140% and 150% (<- dyslexia lol).

some apps also maximize to a slightly incorrect size, causing little lines showing the desktop behind them along the edges of the screen. this is fixable by setting the correct size with Window Settings rules (Size > Apply Initially), but i wondered if it was related to the other issue. i’m not sure if this also depends on zoom level.

as a new user i can only post one screenshot, so here’s the most annoying example:

sorry for the awful phone picture, but it doesn’t appear on spectacle.

some of them are persistent, but others, like the one pictured, pop in and out as i interact. it’s very distracting!

my system is as follows:

distribution: Debian 12 x86_64 stable (bookworm, main, non-free firmware, contribs)
host: 21EBCTO1WW ThinkPad E14 Gen 4
Plasma version: 5.27.5
window manager: kwin
protocol: Wayland
CPU: AMD Ryzen 3 5425U
GPU: AMD ATI 04:00.0 Barcelo

output of kscreen-doctor --outputs:

Output: 1 eDP-1 enabled connected priority 1 Panel Modes: 0:1920x1080@60*! 1:1680x1050@60 2:1280x1024@60
3:1440x900@60 4:1280x800@60 5:1280x720@60 6:1024x768@60 7:800x600@60 8:640x480@60 9:1280x1024@60 10:102
4x768@60 11:1280x800@60 12:1920x1080@60 13:1600x900@60 14:1368x768@60 15:1280x720@60 Geometry: 0,0 1371x
771 Scale: 1.4 Rotation: 1 Overscan: 0 Vrr: incapable RgbRange: unknown

it happens on all stock themes.

display settings:
as i said my screen is set to 140% zoom; no overscan, and legacy applications apply scaling themselves.

i installed Debian on another, much older Thinkpad from the same USB drive and it doesn’t have the same issue. KDE was selected during installation on both laptops. the installer was burned from an iso on Debian’s website and i regularly update && upgrade, so i’m up to date (with Debian, not KDE lol).

possibly related issue: “weird glitch on top left corner” (i can’t post a link, but it’s a recent post)

thanks a lot for reading!

Hi! Just to double-check, it sounds like the odd visual artifacts that you’re noticing don’t show up on a screenshot from the device itself? Do they disappear while you’re taking the screenshot, or do they still appear while using Spectacle but are missing from the actual screenshot image?

And when you’re mentioning the “zoom” level of the system, are you referring to the Scale setting below?

Does the issue show up in an X11 session? And, are you able to create and boot a Live USB of a distribution with more up-to-date KDE software (Fedora, Endeavour OS, etc.) to see if the issue shows up there?

I’m only asking that last part as, at least in my personal experience, a metric ton of improvements have been made to the Plasma Wayland session since version 5.27.5, and those improvements will presumably never show up in Debian 12.

I’ll have a look at that later when I can sit down with it, thanks for the tip John and Megh. I have some bootables ready to go.

To answer two of your questions now: yes, I do mean the scale slider in the display settings (I realized kscreen-doctor says the same thing; Scale: 1.4). not all the bugs disappear when I screenshot, but some do. here’s a screenshot of a bug:

(bottom left)

It can be hard to get them because they pop in and out of existence.

I’ll report back when I try your suggestions! Thanks again!

Okay, I booted into OpenSUSE live (tumbelweed) and mucked about. And wow did I learn a lot!

Not only does it still happen with an up to date KDE/Wayland, but it happens in X11 too. The exact same stuff. X11 told me I needed to use multiples of 6.25% to avoid visual glitches and set it to 137.5% instead, but it still happened. I tried following the 6.5% rule in Wayland too but it didn’t allow half steps, and was no better at 137%.

edit: at this point I’m thinking I should try a different desktop enviornment and see if it actually has anything to do with KDE, too.

1 Like

That could be a good diagnostic move! You could create a Live USB of something like Ubuntu 24.10 or Fedora Workstation 41, and get a pretty recent kernel + GNOME environment to see if the issues persist there.

If it’s still a problem there, then it might come down to some lower-level interaction between your display adapter and the kernel drivers. That wouldn’t be totally unheard of for AMD graphics, as it looks like some other folks over on the Fedora Discussion boards have recently seen similar-sounding issues? Major problem with display on Fedora PLEASE HELP - Fedora Discussion

I had a live Debian with XFCE on it so I used that. And nope, no problems there; it can scale just fine.

I’ll try making a Fedora+GNOME drive later on and see if I get the same issue; it does seem like they are having the exact same issue as me over there.

Thanks for the help!

Okay, I made a live USB with Fedora Silverblue on it and messed around with it. I didn’t encounter any issues at all.

So it’s 1. only KDE, 2. any KDE, and 3. only this machine.

(๑•﹏•)⋆

Hmm - OK, some other random ideas here based on other similar-sounding issues :slight_smile:

No luck unfortunately, still happens after forcing no triple buffering and no colour management.

That one is Highlight the lines coming into view from the Scrolling section of profile configuration.

1 Like

Oh wow! Thank you!

Disabling it did stop that one. However, the lines in the middle of the field do still keep appearing, as do the other irregularities around the edges of windows.

That explains why I could screenshot that one.

Update: I was using that Fedora live usb that has a GNOME enviornment and actually it started happening on it in the gnome terminal after a while. Not sure if it’s related, but perhaps it isn’t exclusive to KDE. It didn’t happen on any other apps apart from the terminal on that enviornment.

Also update: disabling ‘highlight the lines coming into view’ actually didn’t disable that bar from appearing after all, it came back XD

I’ve reinstalled Debian on the laptop (for various reasons) and I’ve instead chosen to keep the display scale at 100% and just set the zoom on apps on a per app basis. Most things have their own zoom, so it works out okay. If I need to see something up close and it’s being stubborn I can magnify with super+= .

I wouldn’t say the issue is solved, but it’s a fine workaround.