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Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors?

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On 2026-01-22 5:09 a.m., Nuno Silva wrote:
> On 2026-01-21, Robert Riches wrote:
> 
>> 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 websites
>>>> 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.
>>> That'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
>>> 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. 
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
expected. (I'm also using a 27" 4K monitor at 163 DPI like the previous
poster.)

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Thread

[On-Topic] any favorite tutorials or other helps for high-DPI monitors? Robert Riches <spamtrap42@jacob21819.net> - 2025-12-25 04:15 +0000
  Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? The Natural Philosopher <tnp@invalid.invalid> - 2025-12-25 11:45 +0000
    Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? Robert Riches <spamtrap42@jacob21819.net> - 2025-12-26 02:03 +0000
  Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? John-Paul Stewart <jpstewart@personalprojects.net> - 2025-12-25 21:38 -0500
    Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? Robert Riches <spamtrap42@jacob21819.net> - 2025-12-26 03:55 +0000
      Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? John-Paul Stewart <jpstewart@personalprojects.net> - 2025-12-26 11:10 -0500
        Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? Robert Riches <spamtrap42@jacob21819.net> - 2025-12-31 05:00 +0000
    Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? c186282 <c186282@nnada.net> - 2025-12-26 00:03 -0500
    Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? Robert Riches <spamtrap42@jacob21819.net> - 2026-01-15 05:09 +0000
      Xorg drivers overriding display resolution (was: Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors?) Nuno Silva <nunojsilva@invalid.invalid> - 2026-01-15 11:20 +0000
    Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? Robert Riches <spamtrap42@jacob21819.net> - 2026-01-21 22:54 +0000
      Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? Nuno Silva <nunojsilva@invalid.invalid> - 2026-01-22 10:09 +0000
        Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? John-Paul Stewart <jpstewart@personalprojects.net> - 2026-01-22 09:34 -0500
          Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? Robert Riches <spamtrap42@jacob21819.net> - 2026-01-23 04:23 +0000
  Re: [On-Topic] any favorite tutorials or other helps for high-DPI monitors? c186282 <c186282@nnada.net> - 2025-12-26 00:00 -0500

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