Question about screen resolution in plasma 5 using x11 and a 4 K monitor arrangement.

Stakanov stakanov at
Mon Mar 14 15:26:02 GMT 2022

In data lunedì 14 marzo 2022 12:49:29 CET, Duncan ha scritto:
> Patrick Nagel posted on Sun, 13 Mar 2022 09:09:44 +0000 (UTC) as
> excerpted:
> > Hi Stakanov,
> > 
> > 13.03.2022 09:56:02 Stakanov <stakanov at>:
> >> It came to my mind that maybe the Plasma desktop cannot be resolved
> >> over the proposed 2160x1140.
> >> 
> >> Could you tell me if plasma has a resolution limit and maybe cannot
> >> fully resolve 4K? This would help me very much.
> > 
> > I'm running Plasma 5.22 (and have been running other 5.x versions) on a
> > 4k monitor without issue. Also using X11 on Kubuntu with Nvidia GPU
> > though.
> I've been running plasma from live-git-master for years, on xorg until a
> bit over a year ago, on wayland since (I took advantage of covid down time
> to do the big switch, originally having to hack-patch a lot of bug
> workarounds, now most are fixed).
> Plasma definitely does 4K, even dual 4K, as I've been using dual 4K big-
> screen TVs as monitors now for several years, since well before the switch
> to wayland so I know it works on both xorg and wayland.
> Tho with dual monitors plasmashell will place a different wallpaper and
> activity on each, not one spread across both (tho the virtual desktop
> combines both activities/monitors).
> It's a Radeon graphics system too, tho an older one from about a decade
> ago, polaris-11 chip family, AMD Radeon RX 460 with 4 gig graphics card
> RAM, 16 gig system RAM.  Running Gentoo ~amd64 (the ~ indicates testing,
> not stale^h^hble), currently mesa-22.0.0, kernel 5.17.0-rc8 (released
> yesterday/Sunday).  I actually no longer have xorg installed so the only X
> I have is xwayland running on wayland.
> The card has three outputs, HDMI, DP, DVI (unused), with a DP-HDMI cable
> on the DP so both TVs are connected via HDMI ports.
> At least back on xorg, tho, I did initially have problems getting
> 3840x2160 at full 60 Hz, it'd only give me 30 Hz, until I found a setting
> I had wrong on the TVs.  IIRC it wasn't set to UHD or something, so
> wouldn't give me 60 Hz at native resolution, only 30 Hz, or lower
> resolution.  Of course I had that worked out long before I switched to
> wayland, so I don't know what plasma-wayland would have done with it.
> So check that.  Perhaps your monitor will do UHD aka 3840x2160 at 60, but you
> need to switch something to get it to do that (apparently it's a common
> option on 4K TVs, no idea on non-TV monitors), and for some reason without
> that available to it, xorg or kde is preferring the lower resolution but
> higher frequency to the lower frequency 3840x2160 at 30 that I got.
> Tho I may have gotten that because on xorg I did have the xorg
> configuration (files in xorg.conf.d) set to 3840x2160 for both outputs.  I
> guess it might have tried the lower resolution higher frequency if I
> didn't have it specifically configured for the native resolutions.
> Meanwhile, I have the kernel configured for framebuffer use instead of the
> legacy vgabuf, with the builtin kernel commandline (CONFIG_CMDLINE)
> including: video=HDMI-A-1:3840x2160 video=DVI-D-1:3840x2160 , and I get
> exactly that for text mode, tho it's duped to both outputs as I've not
> figured out how to do different on each for text mode, if it's even
> possible at all.  (I don't use a graphical login, booting to a textmode
> login prompt from which I login, and if I want to go graphical I start
> kde, now wayland mode formerly xorg mode, from the CLI.  I have weston
> installed and configured so I can run it from the CLI instead, if the
> after all live-git plasma session won't run.)
> Another suggestion:  Try running xrandr (without options should be fine)
> in a konsole window, and see if it lists 3840x2160 there.  If you see the
> option there, X should be able to do it and it's probably a kde-plasma
> thing.  If the resolution isn't listed there, X doesn't think it's
> possible either, and you'll need to figure out how to get X to see it
> first.  (There's several different ways to get and then feed X the
> necessary modeline info; I always used a modeline generator, there's some
> on the web as well as X utilities available, and setup the xorg.conf
> config with it.)
> If it's listed, you can try running xrandr --help and figure out the
> xrandr syntax needed to try switching to it with xrandr instead of using
> kscreen or whatever.  If xrandr will switch to it you have confirmation
> that it's a kde/plasma problem; if xrandr tries to switch but the result
> is garbled or there are other problems, maybe kde is detecting those and
> refused it as a result.
> ** Do be aware, however, with multiple monitors at least, I often have (on
> wayland now, but back on xorg too) problems with plasmashell switching
> activities and panels to the wrong monitors if I do resolution switches.
> I can usually recover, but sometimes it's just easier to quit back to the
> CLI and start a new kde session.  So save all your work and be prepared to
> exit your kde session and start a new one if necessary, before you start
> messing with resolution switches. **
> Other than that, I'll second the suggestion to try booting another distro,
> from a USB stick or something.  But plasma can definitely handle at least
> side-by-side 4K, totaling 7680x2160, on both xorg and wayland, because
> I've been doing that for years.
Infact, Xrandr gives:
Screen 0: minimum 320 x 200, current 4944 x 1440, maximum 16384 x 16384
DisplayPort-0 connected 1920x1080+0+180 (normal left inverted right x axis y 
axis) 509mm x 286mm
   1920x1080     60.00*+  50.00    59.94  
   1600x1200     60.00  
   1680x1050     59.88  
   1400x1050     59.95  
   1280x1024     75.02    60.02  
   1440x900      74.98    59.90  
   1280x960      60.00  
   1360x768      60.02  
   1280x800      60.00  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
   720x400       70.08  
DisplayPort-1 disconnected (normal left inverted right x axis y axis)
DisplayPort-2 disconnected (normal left inverted right x axis y axis)
DisplayPort-3 connected primary 2560x1440+2384+0 (normal left inverted right x 
axis y axis) 698mm x 393mm
   2560x1440     59.95 +  74.97* 
   1920x1200     59.88  
   1920x1080     60.00    50.00    59.94  
   1600x1200     59.95  
   1680x1050     59.95  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1440x900      59.89  
   1280x800      59.81  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    60.00  
   832x624       74.55  
   800x600       75.00    60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  

So it thinks I cannot do it. But the specs say I can. That is strange.
I will have to write Lenovo if this monitor was produced with charge that 
cannot do the resolution? 

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