How to revert per monitor scaling?

kz-n · November 9, 2024, 1:36pm

So I have 2 monitors which are the same inch size but one has a smaller resolution, this caused it to be considered much bigger by apps and whatsonot, so i tried looking for some ways to scale it down, It didn’t really work but it left an annoying side effect that i can’t get rid of which is wherever there’s a QT window on my monitor where I tried to decrease the size, it just gets rendered wrong, almost like its insanely bigger

Example on VLC with the main monitor and then the affected monitor. Pls help

eso · November 9, 2024, 4:39pm

@kz-n ,
Try to find scaling factors in System Settings / Display Confirutation when the size of the screens look close by size.

kz-n · November 9, 2024, 10:12pm

It isn’t being scaled by KDE, I remember setting an environment variable, config or file of some kind to achieve that, but i can’t for my life remember where that is

eso · November 10, 2024, 10:09am

@kz-n
I would check the Autostart what visible script or commands may cause the undesireable settings.
If you want to overwrite the setting by another script use
kscreen-doctor -o # this output shows the best mode(s) marked by colours
kscreen-doctor -o | grep Output:
shows your output devices
In my case a test script seems to do some settings
I may be wrong the scaling factor modifies the offset reciprocally.
But the simplest way is the graphical tool.

#!/bin/bash
kscreen-doctor output.HDMI-A-1.enable \
               output.HDMI-A-1.mode.25 \
               output.HDMI-A-1.position.0,0 \
               output.HDMI-A-1.scale..65 \
               output.eDP-1.mode.1 \
               output.eDP-1.position.1969,0 \
               output.eDP-1.scale..95

kz-n · November 10, 2024, 6:40pm

isn’t kscreen-doctor the same functionality as the gui in the system settings? my problem is not related to that, i was trying to scale my external monitor down (because since it has the same inch size but smaller resolution, the UI in it appears bigger than my main monitor) and i specifically couldn’t do that with the gui in the system settings ,so i was trying to use a different way but i don’t remember how to revert it

eso · November 10, 2024, 7:11pm

It’s hard to help you if you do not give enough information.
Are you on wayland or X-11?
Show us the output of
loginctl show-session 2 -p Type
and
kscreen-doctor -o

kz-n · November 10, 2024, 8:09pm

Yes, I am on X11, I tried to look for ways to scale my external monitor down, so it was something from google results but i can’t for my life find out what I searched for.

Output: 473 eDP-1-1
        enabled
        connected
        priority 1
        Panel
        Modes:  478:1920x1080@60*!  479:1920x1080@60  480:1920x1080@60  481:1920x1080@60  482:1920x1080@60  483:1680x1050@60  484:1680x1050@60  485:1400x1050@60  486:1600x900@60  487:1600x900@60  488:1600x900@60  489:1600x900@60  490:1280x1024@60  491:1400x900@60  492:1400x900@60  493:1280x960@60  494:1440x810@60  495:1440x810@60  496:1368x768@60  497:1368x768@60  498:1280x800@60  499:1280x800@60  500:1280x800@60  501:1280x800@60  502:1280x720@60  503:1280x720@60  504:1280x720@60  505:1280x720@60  506:1024x768@60  507:1024x768@60  508:960x720@60  509:928x696@60  510:896x672@60  511:1024x576@60  512:1024x576@60  513:1024x576@60  514:1024x576@60  515:960x600@60  516:960x600@60  517:960x540@60  518:960x540@60  519:960x540@60  520:960x540@60  521:800x600@60  522:800x600@60  523:800x600@56  524:840x525@60  525:840x525@60  526:864x486@60  527:864x486@60  528:700x525@60  529:800x450@60  530:800x450@60  531:640x512@60  532:700x450@60  533:700x450@60  534:640x480@60  535:640x480@60  536:720x405@60  537:720x405@59  538:684x384@60  539:684x384@60  540:640x400@60  541:640x400@60  542:640x360@60  543:640x360@60  544:640x360@60  545:640x360@59  546:512x384@60  547:512x288@60  548:512x288@60  549:480x270@60  550:480x270@60  551:400x300@60  552:400x300@56  553:432x243@60  554:432x243@60  555:320x240@60  556:360x202@60  557:360x202@59  558:320x180@60  559:320x180@59 
        Geometry: 0,0 1920x1080
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: unknown
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: incapable
        Color profile source: incapable
Output: 474 HDMI-1-1
        disabled
        connected
        priority 0
        HDMI
        Modes:  493:1280x960@60  501:1280x800@60  507:1024x768@60  522:800x600@60  523:800x600@56  535:640x480@60  560:1366x768@60!  561:1920x1080@60  562:1920x1080@60  563:1280x1024@75  564:1152x864@75  565:1280x720@60  566:1280x720@60  567:1024x768@70  568:800x600@72  569:800x600@75  570:720x480@60  571:720x480@60  572:640x480@75  573:640x480@73  574:640x480@60  575:720x400@70 
        Geometry: 0,0 1366x768
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: unknown
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: incapable
        Color profile source: incapable
Output: 475 DP-1-1
        disabled
        disconnected
        priority 0
        DisplayPort
        Modes: 
        Geometry: 0,0 0x0
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: unknown
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: incapable
        Color profile source: incapable
Output: 476 HDMI-1-2
        disabled
        disconnected
        priority 0
        HDMI
        Modes: 
        Geometry: 0,0 0x0
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: unknown
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: incapable
        Color profile source: incapable

eso · November 10, 2024, 8:53pm

So why not to install arandr and interactively play with it. Use the commit tick and Save as to
~/.screenlayout/monitor.sh
chmod +x ~/.screenlayout/monitor.sh
OR save this in a file (di.sh) chmod +x di.sh and run it

#!/bin/bash
kscreen-doctor output.HDMI-1-1.enable \
               output.HDMI-1-1.mode.561 \
               output.HDMI-1-1.position.0,0 \
               output.HDMI-1-1.scale.1\
               output.eDP-1.mode.478 \
               output.eDP-1.position.1920,0 \
               output.eDP-1.scale.1

Yes, the physical sizes are different. Modify the scale and if main menu appears on the HDMI (left) screen the 2nd position should be 1920*(1/scale of HDMI) if that makes sense.

kz-n · November 10, 2024, 10:18pm

I don’t want to change the size of my monitor anymore, I just want to revert what I had tried to do, I don’t know how else to explain my issue but with the screenshot in the OP where vlc on my main monitor looks fine but then looks scaled up and weird on my secondary

eso · November 11, 2024, 9:54am

@kz-n
Sorry, I misunderstood your question. Try a scale factor that suits you / fits your monitor.

QT_SCALE_FACTOR=1.4 vlc

Should you want to find where and what has changed in this respect:

history | grep QT_SCALE

find . -type f -exec grep -H 'QT_SCALE_FACTOR' {} \;

kz-n · November 11, 2024, 6:56pm

setting the qt scale factor to a number under zero does show vlc acting in that manner even on my main monitor, searching history for QT_SCALE didnt return anything apart from the commands i just did, and the find command seems to run infinitely (i noticed it taking forever on ~ so i added | pv > /dev/null and it was “moving” at 0B/s)