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flocntl

Member

Registered: 2007-10-02

Posts: 29

Can I trust the DPI setting calculated by Xorg?

Hello. I have a Dell U2412M 24" 1920x1200 monitor. xdpyinfo reports the following:

$ xdpyinfo | grep -B2 resolution
screen #0:
  dimensions:    1920x1200 pixels (508x318 millimeters)
  resolution:    96x96 dots per inch

According to the specifications on the Dell site, the display's dimensions should be:

Horizontal: 518.4 mm
Vertical: 324.0 mm

So now I'm wondering if the calculated DPI setting is really correct? In the xorg log file I found:

$ cat /var/log/Xorg.0.log | grep -n1 DPI
139-[     6.810] (II) NVIDIA(0): Virtual screen size determined to be 1920 x 1200
140:[     6.816] (--) NVIDIA(0): DPI set to (93, 95); computed from "UseEdidDpi" X config
141-[     6.816] (--) NVIDIA(0):     option

which seems to match my monitor spec more closely than the one reported by xdpyinfo.

I've also tried to set the dimensions manually, but that had no effect at all according to xdpyinfo:

$ vim /etc/X11/xorg.conf.d/90-monitor.conf
Section "Monitor"
    Identifier             "<default monitor>"
    DisplaySize            518.4 324
EndSection

Thanks!

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: Can I trust the DPI setting calculated by Xorg?

Your GUI is probably overriding the DPI to 96x96, as XFCE does.

However, I don't think Nvidia's calculation is particularly accurate.

Your particular monitor is probably extremely close to 96x96 DPI, so it would be reasonable to leave it at 96x96. If you want to experiment with different DPI, look closely at the spacing between fonts, and see if you can find occasional bad spacing.

See thread containing a good collection of DPI info.

graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,734

Website

Re: Can I trust the DPI setting calculated by Xorg?

https://www.sven.de/dpi/

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brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: Can I trust the DPI setting calculated by Xorg?

https://www.sven.de/dpi/

That's a terrible site to recommend.

It's *TWO* values - x and y, horizontal and vertical, up and down. Don't take steps *backwards* in understanding.