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RE: px vs. pt

From: Walter Ian Kaye <walter@natural-innovations.com>
Date: Wed, 2 Aug 2000 08:08:27 -0700
Message-Id: <v04220829b5ade78ce1c1@[63.193.119.97]>
To: www-style@w3.org
At 11:40a -0700 07/27/2000, Todd Fahrner didst inscribe upon an 
electronic papyrus:
>This isn't so. Under Windows, small fonts = 96ppi logical res; large 
>fonts = 120ppi. It's the Mac that has a traditional 72ppi logical 
>res.

It's not just traditional, it's hard-coded into QuickDraw. You cannot 
even change it in OS X -- it's still defined as 72dpi no matter what.

>All of these are quite likely to be wrong for most displays, which 
>is one reason that points are not useful for screen use.

It's not the display's fault; it's however the system has been configured.

>If you feel compelled nevertheless to use points, make sure that no 
>text works out to less than 9pt if you want it to be legible to many 
>Mac users.

And make sure you specify Geneva over Arial (Arial will not even 
display boldface at anything less than 11pt).

>It's not a question of the size of the characters on screen - they 
>might be 10m high each -  it's that there will be insufficient 
>pixels to draw upper- and lower-case roman text recognizably, 
>without clogging up the counters.

right.

>I've got MacIE5 configured correctly to use a 115.5 ppi logical 
>resolution (matching the actual physical res). My preferred font 
>size is 14px (x-height: 7px) for this configuration. I can always 
>tell the bozo sites using points immediately: they're the ones with 
>the absurdly huge fonts. Like CNN, which sniffs my UA string, 
>assumes that I don't/won't/can't/shouldn't configure my UA 
>correctly, and proceeds to serve up "default compensated" CSS 
>containing point units. And some that should know better, like 
>XML.com. It's a good thing MacIE5's got text zoom; I have to reduce 
>to 75% to read these sites unless I'm across the room.

What you're forgetting is that even if you can configure IE, you 
can't configure QuickDraw. The MacOS does not see your 115.5ppi, it 
only sees 72dpi.
So if you wind up with absurdly huge fonts, it's because you're 
trying to fool your system into thinking it's something it's not, and 
that doesn't work. And you can't put the onus on other authors when 
you configure your system in an illogical manner. (I'm talking math, 
not marketing.)

I always run at 72dpi. If I want 1152x870, I buy a 22" monitor.
Until such time as QuickDraw gets some user prefs, anyway.


-Walter
Received on Wednesday, 2 August 2000 11:10:25 GMT

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