Re: [gentoo-user] New monitor, new problem. Everything LARGE O_O

[Frank Steinmetzger <Warp_7@gmx.de>]

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Am Sun, Jul 07, 2024 at 02:06:04PM -0700 schrieb Mark Knecht:
> On Sun, Jul 7, 2024 at 1:09 PM Frank Steinmetzger <Warp_7@gmx.de> wrote:
> >
> > Am Sat, Jul 06, 2024 at 07:32:49PM -0500 schrieb Dale:
> <SNIP>
> >
> > Well don’t mix up frame rate and scaling. 75 Hz vs. 60 is quite subtle,
> you
> > might not even notice 90 Hz. But changing DPI from 80 to 70 will mean an
> > increase in fonts by 14 %.
> 
> So I understand the 14% calculation, but help me understand the underlying
> technology. Is the DPI how a font file, which I presume is some fixed size,
> like 25x25, gets scaled onto the screen? I'm not clear about the conversion
> from the font to the number of dots used to draw the font on the screen.

Yeah. So, big convoluted topic. ^^

First, there is the physical pixel raster of the screen, which determines 
the PPI value. But what may confuse people without knowing (I was very 
confused in my early computing days when I was using Windows): font sizes 
and their units. People usually think in pixels, but font sizes are given in 
point, especially on modern Linux desktops. Historically, Points come from 
lead typesetting, where 1 pt = 1/72 inch. And monitors of early publishing 
machines (and I think at the time in general) all had 72 ppi, so if you have 
a font size of 12 pt == 1/6 in == 4,233 mm on your screen, it will be 
exactly the same size on the printed paper. No scaling necessary.

I forgot some of the minutiae over time; AFAIR Windows 9x+ assumed a standard 
density of 96 ppi and font sizes were set up in pixels in the control panel. 
The monitor market was very homogeneous, there was not much diversity, so no 
need for scaling factors. The default in Windows 2000 and XP was Tahoma at 8 
pixel. And it was the same on Pocket PCs (PDAs with 3″ touch screens of 
240×320). So if you took a screenshot on all of those screens, the font was 
identical to the pixel.

No comes the clash between the logical and the physical world. Today we have
- high-density screens like tablets and laptops: 4K at 14″ equals 315 ppi
- the standard cheap office screen of 1900×1200 at 24″ equals 94 ppi
- my 8 years old Thinkpad with FullHD at 12.5″ and 176 ppi

A text of size 12 pixel will always be 12 pixels high, so it will appear 
smaller to the eye when the pixels are small, and bigger when the pixels are 
big.

OTOH, a text at 12 pt should be displayed physically (in millimeters or 
inches on the screen) at the same size no matter how fine a screen resolves 
an image. So the computer needs to know how many pixels it needs to reach 
that size. That’s where the ppi come in:

                   font size in pt
Number of pixels = --------------- * Screens density in pixel/in
                     1/96 pt/in

The first factor gives you the font’s physical dimension in inch, the second 
factor converts that into pixel height. The units all cancel each other out 
with pixels remaining.

That’s why you can enter the screen’s ppi into the settings (or use it 
automatically, if possible). So the font size you set will be the same to 
your eye no matter what monitor you plug in. The scaling factor business 
hides that: 100 % means 96 ppi, 200 % means 192 ppi.

This produces two “Unfortunately”s:

Unfortunately 1: people don’t know what the scaling means and how it works 
physically.

Unfortunately 2: UI developers stick to this scaling factor idea. Everything 
outside certain values (meaning integer multiples of 96) looks ugly. But 
none of my screens have a ppi of n * 96. They are all inbetween (117, 176, 
216) and when I set the correct scaling, the Plasma UI becomes ugly as hell 
because the previously nice-looking pixel-perfect lines become blurred or 
their thickness varies depending on where on the screen they are drawn.


> > I’m confused. I thought the new one has already arrived and is the one
> where everything was HUGE. %-)
> 
> Dale does this at times and I get confused also. He will (the way I read the
> messages) sometimes be talking about different machines or different
> monitors. His 'main rig", his "new rig", etc.

We could stick to hostnames. *ducksandruns*

-- 
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