On 2025-12-24 11:15 p.m., Robert Riches wrote:
Does anyone have favorite tutorials or other helps for dealing
with a high-DPI transition?
I'm Running Devuan (currently Daedalus, hopefully soon Excalibur)
using plain X and fvwm2, no DE as such with 1920x1200 monitors.
Just purchased a round of 4k monitors, so I'll be needing to
adjust xterm fonts, web browser issues, other GUI application
issues, etc.
It's been a couple years since made a similar switch. But as far as I recall, there's not much to do other than configuring X. I had to
manually specify the monitors' physical size (in millimetres) in my
xorg.conf so that X could calculate the correct DPI. Then everything
that's measured in points just kind of fell into place. (E.g., there
was nothing to be done for LibreOffice, etc.)
On 2025-12-26, John-Paul Stewart <jpstewart@personalprojects.net> wrote:
On 2025-12-24 11:15 p.m., Robert Riches wrote:
Does anyone have favorite tutorials or other helps for dealing
with a high-DPI transition?
I'm Running Devuan (currently Daedalus, hopefully soon Excalibur)
using plain X and fvwm2, no DE as such with 1920x1200 monitors.
Just purchased a round of 4k monitors, so I'll be needing to
adjust xterm fonts, web browser issues, other GUI application
issues, etc.
It's been a couple years since made a similar switch. But as far as I
recall, there's not much to do other than configuring X. I had to
manually specify the monitors' physical size (in millimetres) in my
xorg.conf so that X could calculate the correct DPI. Then everything
that's measured in points just kind of fell into place. (E.g., there
was nothing to be done for LibreOffice, etc.)
After waiting for adapters to arrive (by "super saver" shipping)
and getting the 1.1GB system logs after physically installing the
4K monitors, I got them running at 1920x1200 by putting
"xrandr --output ... --mode 1920x1200" and a couple of sleep
commands in my .Xclients file. Omitting the xrandr commands
brings up X in 3840x2160 mode, but the DPI is stuck at 96.
Xorg.0.log showed the EDID size information being fetched correct
as 597 x 336 mm. However, Xorg.0.log showed the DPI being set to
(96, 96).
So, I created an xorg.conf. Evidently, X11 wants things
specified in terms of two monitors side by side--thus the 1194 by
336. After some experimenting, I put this in /etc/X11/xorg.conf:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv cut here vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv Section "Screen"
Identifier "Default Screen Section"
Monitor "Asus PA279CV"
EndSection
Section "Monitor"
Identifier "Asus PA279CV"
VendorName "Asus"
ModelName "PA279CV"
DisplaySize 1194 336
EndSection
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cut here ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
With that, grepping /var/log/Xorg.0.log for words EDID, mm, and
DPI yields this:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv cut here vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv [179297.003] (II) AMDGPU(0): EDID for output DisplayPort-0
[179297.003] (II) AMDGPU(0): EDID Version: 1.3
[179297.003] (II) AMDGPU(0): clock: 594.0 MHz Image Size: 597 x 336 mm [179297.003] (II) AMDGPU(0): clock: 148.5 MHz Image Size: 597 x 336 mm [179297.003] (II) AMDGPU(0): clock: 297.0 MHz Image Size: 597 x 336 mm [179297.003] (II) AMDGPU(0): clock: 241.5 MHz Image Size: 597 x 336 mm [179297.003] (II) AMDGPU(0): Number of EDID sections to follow: 1 [179297.003] (II) AMDGPU(0): EDID (in hex):
[179297.006] (II) AMDGPU(0): EDID for output DisplayPort-1
[179297.006] (II) AMDGPU(0): EDID Version: 1.3
[179297.007] (II) AMDGPU(0): clock: 594.0 MHz Image Size: 597 x 336 mm [179297.007] (II) AMDGPU(0): clock: 148.5 MHz Image Size: 597 x 336 mm [179297.007] (II) AMDGPU(0): clock: 297.0 MHz Image Size: 597 x 336 mm [179297.007] (II) AMDGPU(0): clock: 241.5 MHz Image Size: 597 x 336 mm [179297.007] (II) AMDGPU(0): Number of EDID sections to follow: 1 [179297.007] (II) AMDGPU(0): EDID (in hex):
[179297.007] (II) AMDGPU(0): EDID for output DisplayPort-2
[179297.007] (II) AMDGPU(0): EDID for output HDMI-A-0
[179297.007] (**) AMDGPU(0): Display dimensions: (1194, 336) mm
[179297.007] (**) AMDGPU(0): DPI set to (163, 163)
[179297.465] (II) event6 - Logitech Trackball: device set to 300 DPI [179297.561] (II) event6 - Logitech Trackball: device set to 300 DPI ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cut here ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The (163, 163) is the correct DPI figure. An earlier DisplaySize
value of 597 336 had yielded a DPI figure of (326, 163). With
either of the DisplaySize values, and even with Xorg.0.log
showing the correct DPI, xdpyinfo still reports DPI as 96x96.
So, it appears that even when Xorg.0.log is showing the correct
DPI, but there's apparently a disconnect between that and
xdpyinfo.
Any suggestions? Thanks in advance!
On 2025-12-24 11:15 p.m., Robert Riches wrote:
Does anyone have favorite tutorials or other helps for dealing
with a high-DPI transition?
I'm Running Devuan (currently Daedalus, hopefully soon Excalibur)
using plain X and fvwm2, no DE as such with 1920x1200 monitors.
Just purchased a round of 4k monitors, so I'll be needing to
adjust xterm fonts, web browser issues, other GUI application
issues, etc.
It's been a couple years since made a similar switch. But as far as I recall, there's not much to do other than configuring X. I had to
manually specify the monitors' physical size (in millimetres) in my
xorg.conf so that X could calculate the correct DPI. Then everything
that's measured in points just kind of fell into place. (E.g., there
was nothing to be done for LibreOffice, etc.)
You'll need to switch your window manager to a high-DPI theme (easy with
my choice, xfwm4) since that's all laid out in pixels and you'll have
tiny icons and title bars if you don't change.
There were very few apps that required any tweaking once X and the
window manager were correctly configured. The venerable 'gv' is the
only one I can think of that required its own DPI setting (in
~/.Xresources) rather than using X's own.
For web browser issues, I anticipate a lot of fun with websitesThat's actually not an issue. HTML/CSS "px" are NOT device pixels but
and web apps that use (n)px directives for some of their margins
and spacing. If the browser interprets those at face value,
mixed with other directives in units of text elements and such,
things could end up looking somewhat different from how the
developers intended.
units of 1/96 inches.[1] In other words, HTML/CSS "px" are standardized
at 96 DPI regardless of actual screen resolution. So if something
specifies 24px it actually means 1/4 inch. On my 4K displays that ends
up being more like 40 device pixels. So websites will still work more
or less as expected.
[1] https://www.w3schools.com/css/css_units.asp
On 2025-12-26, John-Paul Stewart <jpstewart@personalprojects.net> wrote:
On 2025-12-24 11:15 p.m., Robert Riches wrote:
Does anyone have favorite tutorials or other helps for dealing
with a high-DPI transition?
I'm Running Devuan (currently Daedalus, hopefully soon Excalibur)
using plain X and fvwm2, no DE as such with 1920x1200 monitors.
Just purchased a round of 4k monitors, so I'll be needing to
adjust xterm fonts, web browser issues, other GUI application
issues, etc.
It's been a couple years since made a similar switch. But as far as I
recall, there's not much to do other than configuring X. I had to
manually specify the monitors' physical size (in millimetres) in my
xorg.conf so that X could calculate the correct DPI. Then everything
that's measured in points just kind of fell into place. (E.g., there
was nothing to be done for LibreOffice, etc.)
You'll need to switch your window manager to a high-DPI theme (easy with
my choice, xfwm4) since that's all laid out in pixels and you'll have
tiny icons and title bars if you don't change.
There were very few apps that required any tweaking once X and the
window manager were correctly configured. The venerable 'gv' is the
only one I can think of that required its own DPI setting (in
~/.Xresources) rather than using X's own.
For web browser issues, I anticipate a lot of fun with websitesThat's actually not an issue. HTML/CSS "px" are NOT device pixels but
and web apps that use (n)px directives for some of their margins
and spacing. If the browser interprets those at face value,
mixed with other directives in units of text elements and such,
things could end up looking somewhat different from how the
developers intended.
units of 1/96 inches.[1] In other words, HTML/CSS "px" are standardized
at 96 DPI regardless of actual screen resolution. So if something
specifies 24px it actually means 1/4 inch. On my 4K displays that ends
up being more like 40 device pixels. So websites will still work more
or less as expected.
[1] https://www.w3schools.com/css/css_units.asp
For anyone finding this thread in the future, there's another
trick for Firefox. In about:config, set
layout.css.devPixelsPerPx
to a value greater than 1. For a 27" 4K monitor, the monitor's
device DPI is 163, and a value of 1.6 makes the Firefox UI
elements (menu bar, dialogs, etc.) a reasonable size. YMMV on
the value for your situation.
On 2026-01-21, Robert Riches wrote:Yes. On my system layout.css.devPixelsPerPx is set to -1.0 which means
On 2025-12-26, John-Paul Stewart <jpstewart@personalprojects.net> wrote:
On 2025-12-24 11:15 p.m., Robert Riches wrote:
Does anyone have favorite tutorials or other helps for dealing
with a high-DPI transition?
I'm Running Devuan (currently Daedalus, hopefully soon Excalibur)
using plain X and fvwm2, no DE as such with 1920x1200 monitors.
Just purchased a round of 4k monitors, so I'll be needing to
adjust xterm fonts, web browser issues, other GUI application
issues, etc.
It's been a couple years since made a similar switch. But as far as I
recall, there's not much to do other than configuring X. I had to
manually specify the monitors' physical size (in millimetres) in my
xorg.conf so that X could calculate the correct DPI. Then everything
that's measured in points just kind of fell into place. (E.g., there
was nothing to be done for LibreOffice, etc.)
You'll need to switch your window manager to a high-DPI theme (easy with >>> my choice, xfwm4) since that's all laid out in pixels and you'll have
tiny icons and title bars if you don't change.
There were very few apps that required any tweaking once X and the
window manager were correctly configured. The venerable 'gv' is the
only one I can think of that required its own DPI setting (in
~/.Xresources) rather than using X's own.
For web browser issues, I anticipate a lot of fun with websitesThat's actually not an issue. HTML/CSS "px" are NOT device pixels but
and web apps that use (n)px directives for some of their margins
and spacing. If the browser interprets those at face value,
mixed with other directives in units of text elements and such,
things could end up looking somewhat different from how the
developers intended.
units of 1/96 inches.[1] In other words, HTML/CSS "px" are standardized >>> at 96 DPI regardless of actual screen resolution. So if something
specifies 24px it actually means 1/4 inch. On my 4K displays that ends
up being more like 40 device pixels. So websites will still work more
or less as expected.
[1] https://www.w3schools.com/css/css_units.asp
For anyone finding this thread in the future, there's another
trick for Firefox. In about:config, set
layout.css.devPixelsPerPx
to a value greater than 1. For a 27" 4K monitor, the monitor's
device DPI is 163, and a value of 1.6 makes the Firefox UI
elements (menu bar, dialogs, etc.) a reasonable size. YMMV on
the value for your situation.
IIRC there was a value that would make it get the resolution from the platform.
On 2026-01-22 5:09 a.m., Nuno Silva wrote:
On 2026-01-21, Robert Riches wrote:Yes. On my system layout.css.devPixelsPerPx is set to -1.0 which means Firefox will get the value from the system and everything works as
On 2025-12-26, John-Paul Stewart <jpstewart@personalprojects.net> wrote: >>>> On 2025-12-24 11:15 p.m., Robert Riches wrote:
Does anyone have favorite tutorials or other helps for dealing
with a high-DPI transition?
I'm Running Devuan (currently Daedalus, hopefully soon Excalibur)
using plain X and fvwm2, no DE as such with 1920x1200 monitors.
Just purchased a round of 4k monitors, so I'll be needing to
adjust xterm fonts, web browser issues, other GUI application
issues, etc.
It's been a couple years since made a similar switch. But as far as I >>>> recall, there's not much to do other than configuring X. I had to
manually specify the monitors' physical size (in millimetres) in my
xorg.conf so that X could calculate the correct DPI. Then everything
that's measured in points just kind of fell into place. (E.g., there
was nothing to be done for LibreOffice, etc.)
You'll need to switch your window manager to a high-DPI theme (easy with >>>> my choice, xfwm4) since that's all laid out in pixels and you'll have
tiny icons and title bars if you don't change.
There were very few apps that required any tweaking once X and the
window manager were correctly configured. The venerable 'gv' is the
only one I can think of that required its own DPI setting (in
~/.Xresources) rather than using X's own.
For web browser issues, I anticipate a lot of fun with websitesThat's actually not an issue. HTML/CSS "px" are NOT device pixels but >>>> units of 1/96 inches.[1] In other words, HTML/CSS "px" are standardized >>>> at 96 DPI regardless of actual screen resolution. So if something
and web apps that use (n)px directives for some of their margins
and spacing. If the browser interprets those at face value,
mixed with other directives in units of text elements and such,
things could end up looking somewhat different from how the
developers intended.
specifies 24px it actually means 1/4 inch. On my 4K displays that ends >>>> up being more like 40 device pixels. So websites will still work more >>>> or less as expected.
[1] https://www.w3schools.com/css/css_units.asp
For anyone finding this thread in the future, there's another
trick for Firefox. In about:config, set
layout.css.devPixelsPerPx
to a value greater than 1. For a 27" 4K monitor, the monitor's
device DPI is 163, and a value of 1.6 makes the Firefox UI
elements (menu bar, dialogs, etc.) a reasonable size. YMMV on
the value for your situation.
IIRC there was a value that would make it get the resolution from the
platform.
expected. (I'm also using a 27" 4K monitor at 163 DPI like the previous poster.)
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