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#1 2020-09-24 18:42:50

rolfie
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Registered: 2017-11-25
Posts: 415  

How to scale Lightdm screen

The HW concerned is a AMD X570 chipset with a Ryzen7 3700X and a Radeon RX5500XT graphics card with a 4k 32" monitor via DP.

Beowulf with Lightdm/Mate is up and running with backports kernel and latest firmware. Found a way to tweak the desktop via Mate Tweak to HiDPI/140 dpi, my wife is really happy with the enlarged display.

Now I also would like to scale up the Lightdm logon display. The Username/Password window is lost on the big monitor and very small, hard to read.

I searched a bit, found some hints onto a lightdm-settings utility which is available in Ubuntu and will come into Devuan with Bullseye/Chimaera, and furtheron some strange tweaks I do not fully trust, posted 2/3 years ago.

Any suggestions/experience for the best way to tweak Lightdm also?

Thank you, rolfie

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#2 2020-09-24 19:16:59

Head_on_a_Stick
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From: London
Registered: 2019-03-24
Posts: 1,064  
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Re: How to scale Lightdm screen

You could try using an X.Org configuration file to set the display size and DPI: https://wiki.archlinux.org/index.php/Xo … ze_and_DPI

Run the xdpyinfo command from an unscaled desktop to find the default values. The command is supplied by the x11-utils package.


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#3 2020-09-25 17:04:48

rolfie
Member
Registered: 2017-11-25
Posts: 415  

Re: How to scale Lightdm screen

When I condense that correctly, a new /etc/xprofile should do the job. I added a simple line with xrandr --dpi 140, also tried 70 instead of 140, added the full path, with no effect.

BTW, here is the output from 3 of my PCs with various monitors. First iof all my X470 workstation with a 27" monitor, no tweaks.

:~# xdpyinfo | grep -B2 resolution
screen #0:
  dimensions:    2560x1440 pixels (677x381 millimeters)
  resolution:    96x96 dots per inch
:~# xrdb -query | grep dpi
Xft.dpi:	96.0234375

X570 with ordinary 24" monitor, no tweaks.

:~# xdpyinfo | grep -B2 resolution
screen #0:
  dimensions:    1920x1200 pixels (508x317 millimeters)
  resolution:    96x96 dots per inch
:~# xrdb -query | grep dpi
Xft.dpi:	96

And finally the object of interest, first with settings tweaked to 140 dpi with MateTweak, then reset to default.

:~# xdpyinfo | grep -B2 resolution
screen #0:
  dimensions:    3840x2160 pixels (1016x571 millimeters)
  resolution:    96x96 dots per inch
:~# xrdb -query | grep dpi
Xft.dpi:	70

:~# xdpyinfo | grep -B2 resolution
screen #0:
  dimensions:    3840x2160 pixels (1016x571 millimeters)
  resolution:    96x96 dots per inch
:~# xrdb -query | grep dpi
Xft.dpi:	96.0419921875

What have I overlooked/misunderstood?

rolfie

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#4 2020-09-25 20:15:03

rolfie
Member
Registered: 2017-11-25
Posts: 415  

Re: How to scale Lightdm screen

After some digging I have learned that a xprofile is not used under Debian/Devuan.

Currently I am lost, I haven't found anything useful in the net.

rolfie

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#5 2020-09-25 20:39:32

Head_on_a_Stick
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From: London
Registered: 2019-03-24
Posts: 1,064  
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Re: How to scale Lightdm screen

I suggested an X.Org configuration file, why have you not tried that?

EDIT: for example:

# /etc/X11/xorg.conf.d/00-monitor.conf
Section "Monitor"
   Identifier "eDPI"
   DisplaySize 508 286
EndSection

Use xrandr to find the correct Identifier for your monitor (listed as "connected") and replace 508 286 with the actual horizontal and vertical dimensions of the screen (in millimetres). You will also need to specify the font size in ~/.Xresources:

Xft.dpi: 140

EDIT2: if that doesn't work for LightDM then perhaps try https://askubuntu.com/questions/72486/c … -dpi-for-x

Last edited by Head_on_a_Stick (2020-09-25 21:27:43)


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#6 2020-09-26 16:11:21

rolfie
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Registered: 2017-11-25
Posts: 415  

Re: How to scale Lightdm screen

Head_on_a_Stick wrote:

I suggested an X.Org configuration file, why have you not tried that?

Because I was looking for a way to scale LightDM only.

Head_on_a_Stick wrote:

EDIT2: if that doesn't work for LightDM then perhaps try https://askubuntu.com/questions/72486/c … -dpi-for-x

Some further mining in the net brought me to these pages:
https://wiki.archlinux.org/index.php/Us … _%28GTK%29
https://selivan.github.io/2017/08/16/li … ution.html
https://evren-yurtesen.blogspot.com/201 … plays.html

Well, the xft-dpi tweak just has the effect that the fonts on the greeter screen are scaled with the dpi setting. Nice, but not what I wanted to see. The login window keeps its size, everything looks very squeezed in with 144dpi.

Looked at the available modes on the system.

~# xrandr -q
Screen 0: minimum 320 x 200, current 3840 x 2160, maximum 16384 x 16384
DisplayPort-0 connected primary 3840x2160+0+0 698mm x 393mm
   3840x2160     60.00*+  29.98  
   2560x1440     59.95  
   1920x1200     59.88  
   1920x1080     60.00    59.94    30.00    29.97  
   1600x1200     60.00  
   1680x1050     59.95  
   1600x900      60.00  
   1280x1024     60.02  
   1440x900      60.00  
   1280x800      59.81  
   1280x720      60.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x480       60.00    59.94  
   640x480       60.00    59.94  
   720x400       70.08  
DisplayPort-1 disconnected
DisplayPort-2 disconnected
HDMI-A-0 disconnected

Setting LightDM to 1920x1080 would be nice. The mode is already available, so I don't need to add this.

But: Looks like both the selivan and the evren-yurtesen blogs aim at Ubuntu. When looking at the file system I found that the directory structure and at least some of the file contents of lightdm.conf is different under Beowulf as described.

In the moment, I am lost. Maybe I need to go down the route to use a xorg.conf for a general scaling of the graphics mode. Needs to settle a bit.

Well, I also found a rant in the German Debian forum where somebody tried to scale a 4k monitor and gave up. Was about xfce.

Thank you for your input. rolfie

Last edited by rolfie (2020-09-26 16:12:58)

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#7 2020-09-26 20:57:46

rolfie
Member
Registered: 2017-11-25
Posts: 415  

Re: How to scale Lightdm screen

Digged a bit further in this script issue and found an older German page that described how to configure to run a script via lightdm.conf.

Basically had success to set the greeter screen to 1920x1080, unfortunately with side effects.

Two user accounts are present, mine with native resolution to administrate the PC, and my wife's account with tweaked resolution. Switching users sometimes brings a scaled up login screen, sometimes native resolution. When I logon, it takes seconds to bring up the panel, the usual icons on the desktop, and starting apps shows a delay. When directly logging into my wife's tweaked account, the screen is scaled up a second time.

This performance is not acceptable.

Tomorrow I will remove all tweaks and try a xorg.conf.

rolfie

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