Use of monitors setup that is past 8192 pixels in width

ppryga · 2024-05-25 13:05:02

I've got a setup of 2 4K monitor + FHD monitor. I run Arch Linux with KDE 6. There is a build in Intel UHD 620 graphic card.

I'm able to setup following resolution 4K monitor but limited to FHD + 4K QHD + native FDH monitor.

When I try to enable max configuration with 2x 4K + FDH monitors one of 4K monitors is disabled.

It is not a problem of graphic card, because I'm able to see system booting on all three. Also Windows is able to run this configuration so hardware is ok.
I tried to use custom Xorg configuration with Screen 0 virtual size set to required resolution or even larger (16384 x 16384) because this is my GL_MAX_TEXTURE_SIZE.

I don't know where this limit comes from and why it is set to 8192... Any hints how to solve this or workaround?

Trilby · 2024-05-25 13:11:51

I believe 8192 is the maximum virtual screen size for Xorg's default configuration, though this can be overridden to a larger size in Xorg.conf. However, if you are using KDE, is there a reason you're sticking with Xorg rather than wayland?

Last edited by Trilby (2024-05-25 13:12:10)

ppryga · 2024-05-25 13:30:40

Well, actually Wayland is used.

loginctl show-session 1 -p Type
Type=wayland

Then I suppose it should work out of the box...

How can I change the max resolution in plasma then?
I can't find this information in documentation...

Last edited by ppryga (2024-05-25 13:53:05)

seth · 2024-05-25 13:53:06

Then your xorg config is rather poointless…

There're possibly more relevant limits (notably some buffers)

glxinfo -l | grep 8192

I don't think X11 is limited to 2^13

xrandr --output <output> --panning 9000x1200

, but your HW certainly might be.

It is not a problem of graphic card, because I'm able to see system booting on all three.

But they're all showing the same output, right?

ppryga · 2024-05-25 14:11:40

seth wrote:

There're possibly more relevant limits (notably some buffers)
glxinfo -l | grep 8192

glxinfo -l | grep 8192
    GL_MAX_UNIFORM_LOCATIONS = 81920
    GL_MAX_UNIFORM_LOCATIONS = 81920

seth wrote:

I don't think X11 is limited to 2^13
xrandr --output <output> --panning 9000x1200
, but your HW certainly might be.

This command fails:

xrandr --output DP-5 --panning 9000x1200
X Error of failed request:  BadRRCrtc (invalid Crtc parameter)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  29 (RRSetPanning)
  Crtc id in failed request: 0x20
  Serial number of failed request:  37
  Current serial number in output stream:  37

DP-5 is the 4k screen but limited to FHD resolution.
The xrandr shows max to be 32767

Screen 0: minimum 16 x 16, current 7680 x 2160, maximum 32767 x 32767

seth wrote:

But they're all showing the same output, right?

In case of linux booting they show the same content. In case of Windows the desktop is expanded over all screens. This is why I assume the HW is not an issue here.

The xorg.conf didn't change anything, taking into account the session runs with Wayland, that is expected.

I suppose I'm not first person that wants to use 2x4K + some other screen setup with Arch.

seth · 2024-05-25 14:18:58

This command fails:

Did you try that in a wayland session?
(Because, yeah - that's not gonna work)

=> Actually try plasma on X11, the kwin compositor may or not bail on that.

ppryga · 2024-05-25 14:57:40

I switched to X11 and the command

 xrandr --output <output> --panning 9000x1200

finished successfully.

In the maeantime I've checked if change of xorf.conf:

Section "Screen"
        Identifier "Screen0"
        Device     "Card0"
        Monitor    "Monitor0"
        [...] 
        SubSection "Display"
                Viewport   0 0
                Depth     24
                Virtual 16384 16384 <<= extended virtual screen
        EndSubSection

But it doesn't change anything. The behavior is the same as with Wayland.

seth · 2024-05-25 15:27:19

"xorg.conf" and that's not a valid config file and xorg configurations will not impact wayland where the restriction is apparently located.
Does kwin compositing (translparency, shadows, animations) still work w/ the larger output configuration on X11?

ppryga · 2024-05-25 16:25:31

seth wrote:

"xorg.conf" and that's not a valid config file and xorg configurations will not impact wayland where the restriction is apparently located.
Does kwin compositing (translparency, shadows, animations) still work w/ the larger output configuration on X11?

I've used the xorg.conf with extended virtual screen resolution to check one of possible workarounds for X11. I know it will not affect Wayland. The point was to check if that works at all.
It doesn't, so in my head, the problem is somewhere deeper, because both X11 and Wayland behave the same way.

And it looks like the problem is related what Arch has in the distribution. Ubuntu for example is able to run such setup (tested with other PC some time ago).

seth · 2024-05-25 16:44:33

tested with other PC some time ago

Remove your xorg config attempt, start an openbox session (to take out the various plasma GL contexts) on X11 (idem) and try to configure your desired layout w/ xrandr there.
Post all xrandr outputs.
Edit: and obviously also the commands that triggered them.

Last edited by seth (2024-05-25 16:45:36)

Arch Linux

#1 2024-05-25 13:05:02

Use of monitors setup that is past 8192 pixels in width

#2 2024-05-25 13:11:51

Re: Use of monitors setup that is past 8192 pixels in width

#3 2024-05-25 13:30:40

Re: Use of monitors setup that is past 8192 pixels in width

#4 2024-05-25 13:53:06

Re: Use of monitors setup that is past 8192 pixels in width

#5 2024-05-25 14:11:40

Re: Use of monitors setup that is past 8192 pixels in width

#6 2024-05-25 14:18:58

Re: Use of monitors setup that is past 8192 pixels in width

#7 2024-05-25 14:57:40

Re: Use of monitors setup that is past 8192 pixels in width

#8 2024-05-25 15:27:19

Re: Use of monitors setup that is past 8192 pixels in width

#9 2024-05-25 16:25:31

Re: Use of monitors setup that is past 8192 pixels in width

#10 2024-05-25 16:44:33

Re: Use of monitors setup that is past 8192 pixels in width

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