Vendor logo does not display in correct ratio on external monitor as it have different ratio than internal on

[Yuan-Chen Cheng]

As Ubuntu boots up, the vendor logo will be retrieved and displayed on the monitor.

Per test, as internal and external monitors have different Wide/Hight ratios, Plymouth will use the monitor ratio of the internal monitor, and the vendor logo will be displayed on both monitors.

Some laptops can boot up even as it's the lid is close, and use the external monitor, keyboard, and mouse only.

For that case:

- internal monitor: off
- external monitor: display the vendor still in the internal monitor ratio.

Which is ok but not perfect.

[Daniel van Vugt (vanvugt)]

It's probably the choice of graphics mode that's making pixels non-square, and probably is not specific to the vendor logo(?)

Can you provide output from 'lspci -kv' ?

[Daniel van Vugt (vanvugt)]

Please use one of the plymouth.debug kernel parameters to record a plymouth log of the problem happening and then attach the log here.

See https://gitlab.freedesktop.org/plymouth/plymouth/-/raw/main/docs/development.txt

[Yuan-Chen Cheng (ycheng-twn)]

when a 1920x1200 monitor is plugged via hdmi port of the machine.

[Yuan-Chen Cheng (ycheng-twn)]

when 1920x1200 external monitor is plugged via wd19 (dell docking)

[Yuan-Chen Cheng (ycheng-twn)]

when 1920x1200 external monitor is plugged via wd19 (dell docking)
and the lid of the laptop is closed.

[Yuan-Chen Cheng (ycheng-twn)]

xrandr as lid of the laptop is closed, and the 1920x1200 monitor is connected via wd19

[Daniel van Vugt (vanvugt)]

Thanks. Those logs say the preferred mode is 1920x1080 so indeed you will see some aspect distortion if that's referring to a 1920x1200 monitor...

Next we need to find out if either:

(a) the incorrect preferred mode is coming from the kernel; or

(b) plymouth is applying the preferred mode of the laptop panel to the external monitor.

Please run 'drm_info' while only the external monitor is connected and the laptop lid is still closed, and attach the output here. drm_info is not in the archive until hirsute but it's a very simple program you should be able to get running: https://launchpad.net/ubuntu/+source/drm-info

[Daniel van Vugt (vanvugt)]

It's starting to look like this is a Plymouth bug/feature where it applies the same resolution to all monitors:

https://gitlab.freedesktop.org/plymouth/plymouth/-/issues/119
https://gitlab.freedesktop.org/plymouth/plymouth/-/issues/9

If true then that would make sense. Plymouth uses software rendering and possibly can't afford to render multiple monitors separately, at least when they are all turned on. If that's the problem then it sounds like Plymouth needs to be made smarter and not include the closed laptop screen in the list of outputs to render. Then there would only be one choice for the correct resolution.

[Yuan-Chen Cheng (ycheng-twn)]

drm_info as 1920x1200 monitor connect to WD19, and lid closed.

[Daniel van Vugt (vanvugt)]

Thanks. It looks like comment #10 is correct. Also the kernel is correctly reporting that the laptop display is OFF and the external monitor is ON. So I think Plymouth should be enhanced to check that and not bother with outputs that are OFF. Then it would only be driving one monitor and the minimum resolution would be the correct resolution = 1920x1200.

[Daniel van Vugt (vanvugt)]

It's a pity the "scaling mode" property is only implemented on the laptop screen because if it existed for external monitors then we could fix this bug by simply setting:

  "scaling mode" = "Full aspect"

[Daniel van Vugt (vanvugt)]

I'm not sure this /should/ be fixed.

We don't want Plymouth to drive separate displays differently (unless it already does?) because that's double the render load, which is too much for software rendering.

We could implement the fix suggested in comment #12, but upstream might not like it for good reason. If some user has a monitor accidentally turned off and plymouth is stuck then they should be able to turn it on halfway through and plymouth should be outputting to it.

If it was my machine I would just search through the monitor's own OSD menu and find the setting that enables use of correct aspect ratios for non-native modes. ;)

[Daniel van Vugt (vanvugt)]

Oh maybe we could fix this in Plymouth without disabling the laptop display...

If the CRTC_X / CRTC_Y / CRTC_W / CRTC_H properties behave how I think they should then we could use them to maintain correct aspect ratio and each monitor in its own native preferred resolution.

For example, displaying a 1920x1080 buffer in a 1920x1200 mode:

  CRTC_X = 0
  CRTC_Y = 60
  CRTC_W = 1920
  CRTC_H = 1080

Maybe those only exist for atomic KMS drivers though (like i915).

https://01.org/linuxgraphics/gfx-docs/drm/drm-kms-properties.html