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Re: 16px default, SI meter (Re: platform-specific font size issues)

From: Todd Fahrner <fahrner@pobox.com>
Date: Wed, 16 Dec 1998 17:43:45 -0800
Message-Id: <v04011702b29dfdcfd0b1@[206.245.203.103]>
To: Susan Lesch <lesch@macvirus.com>, www-style@w3.org
Thus spake Susan Lesch :

 " If you are looking for a new definition for the reference pixel,
 perhaps, like DSSSL and early XSL, CSS lengths could be based on the SI
 meter? Or are inches becoming a U.N. recommendation? :-)

By my reading of CSS1, the "real" suggested reference pixel is a degree of
visual angle. The conversion to inches (1/90") merely provides an example
of what this works out to at arm's length. Wonder if Hakon or Bert can
comment.

 " > The appropriate corrective measure, I submit, is for Mac (and X11?)
 " > browsers to break with tradition and ship with the default value of
 " > "medium" text set at 16px, instead of 12pt.
 "
 " Microsoft tried something like this in MSIE 4.0 Mac, where 'medium' was
 increased to 14. They changed it back to 12 in version 4.01.

Are you sure about that? I hadn't noticed. That was a "trade-show special"
release - loaded with bugs. Tantek - was there an experiment in 4.0? Or was
this just a bug?

 " I don't know about UNIX setups, but your suggestion seems to work fine
 with the new 1.2 scaling factor between keywords in CSS2 [1]:
 "
 " xx-small  9.24 (for most fonts, the smallest readable size on a Mac)

Good point. Actually, 9px (literal pixels) is the smallest legible size for
just about any bicameral script on any platform. Try it. Note that Netscape
4 and current NGLayout builds mis-render 9px at the illegible 8px, however.

 " x-small  11.08
 " small    13.33
 " medium   16
 " large    19.2
 " x-large  23.04
 " xx-large 27.65
 "
 " (My only worry is that such large type takes up so much screen real
 estate that it might make navigation slower and more complex on all but
 the most high-end setups for many years to come.)

Heh. 200 million Windows installs can't be wrong, can they? 16px is the
current Windows UA default. Hence all the Web designers trying to crank it
down, redundantly with user efforts, and to the great detriment of
readability on the 12px-base Mac.

There's a danger in taking this 1.2 scaling factor too literally. If
"medium" starts out below 16px, then xx-small is guaranteed to be illegible
unless you adjust.

Here's a thought experiment in how the keyword values could adapt as the
user changes hir "medium" value:

If medium is 16px, then the following values should obtain for the keywords:
xx-small  9px
x-small  12px
small    14px
medium   --
large    20px
x-large  24px
xx-large 28px

If medium is 14px...:
xx-small  9px
x-small  10px
small    12px
medium   --
large    18px
x-large  22px
xx-large 26px

If medium is 12px...:
xx-small  9px
x-small  10px
small    11px
medium   --
large    14px
x-large  18px
xx-large 22px

...and so on.

The upshot? UI should caution users against setting the value of "medium"
to below 12px, as it will be hard/impossible to render the various small
values distinctly and legibly beneath such a base.

Next you'd need to make sure that the ex-height of the user's serif, sans,
script, and "fantasy" default fonts got recorded in the user/UA default.
Then whenever another face was specified, the UA could apply the font-size
adjust property to normalize the ex-heights across default and specified
faces.

--
Todd "I want my ex-unit!" Fahrner
Received on Wednesday, 16 December 1998 20:43:59 GMT

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