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Comment by gcb | Hacker News Reader

i was fighting with the same thing the other day... then i realized, i do not look at my 24" monitor at the same distance then i look at my 4" phone screen.

So, which size should the font be if i'm designing for both those screens? pt sure isn't the answer.

this being only tangentially related to the topic :) so, back on topic, yes, i wholeheartedly agree that pt should mean what it mean. it's just retarded that it's not. and you are not even accounting for TVs which cut random portions of the displayed image for no reason, making this even harder to calculate the real dpi.

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Ironically there is a straightforward answer: arc distance. What angle does the font (or pixel, or whatever you're trying to scale) subtend from the position of your eye? This works always. It's sometimes hard to define for some devices (e.g. TV's, which might be used a widely varying distances), but even then the world has come up with standard conventions (e.g. assume you're 10' from your 40" TV, assume your phone is about 12" away, assume the controls in your car are at a 30" arm length...).

And, of course, it's not implemented anywhere. So we all suffer with "dpi" and "px".

According to CSS 2.1, px _should_ be defined in terms of an angle: http://inamidst.com/stuff/notes/csspx.

That's fun. Obviously that's not how it works, 1px is 1 physical pixel everywhere I've ever seen. Think of how much would break if something decided to do this "right" ...

On retina displays it is two pixels.

I haven't paid too much attention to this but shouldn't it be a square of four pixels? That would be true double resolution, right?

Or is there some pixel trickery like those olpc displays? [http://wiki.laptop.org/go/Display]

px is a measure of length, not area.

A 12 px high font is 24 px high on a retina display.

A 12 px by 12 px box is 144 px^2, or 12 x 12 x 2 x 2 = 576 px^2 on retina.

This works for head-mounted/heads-up displays, too, making it somewhat more future-proof.

Thanks for giving me yet something else tocurse browsers for.

I don't think points is a good fit for that. A point has a defined length, 1/72 of an inch. If you don't want your text to be 12/72 of an inch, don't specify the size in points.

What? That is not the case with any browser. Nor with any software as the article points out.

Would be awesome if it was...

Since the invention of desktop publishing, PostScript points have been 72 to the inch. Resolution-independent rendering was taken into consideration in the 80's. If a "point" is not 1/72 of an inch then it's rendered wrong. https://en.wikipedia.org/wiki/Point_%28typography%29

That's kind of what the article is pointing out...

>So, which size should the font be if i'm designing for both those screens? pt sure isn't the answer.

I think the "small", "medium", "large" etc would be the best choice. Those by definition should be always the correct size.

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