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[css3-fonts] font-size and vertical text (was: Re: [css3-fonts] Minor Comments Part II)

From: John Daggett <jdaggett@mozilla.com>
Date: Mon, 20 May 2013 03:19:48 -0700 (PDT)
To: www-style@w3.org
Message-ID: <838695190.16390589.1369045188470.JavaMail.root@mozilla.com>

fantasai wrote:

> >>>> http://dev.w3.org/csswg/css-fonts/#font-size-prop
> >>>>      # This property indicates the desired height of glyphs from the font.
> >>>>
> >>>> Shouldn't that be "desired size"? Because in vertical typesetting
> >>>> with proportional or non-square glyphs, it's not necessarily the
> >>>> height.
> >>>
> >>> It's generally the height of glyphs and I don't think changing
> >>> this to "size" adds an clarity to the spec.
> >>
> >> I was going more for accuracy than clarity here. If it's not always
> >> the height, then we shouldn't use the term height here.
> >
> > Thinking about your original comment a little more, the
> > 'font-size' property specifies the height of glyphs before layout
> > operations, it's no different for proportional and/or non-square
> > glyphs.  So I think the existing text is just fine, I don't see
> > the need to bring in a discussion of the complexities of vertical
> > text rendering here.  It doesn't add clarity and it doesn't affect
> > what implementations will do.
> 
> I'm not sure it's a complexity of vertical text. It's just that if
> you have a non-square font, in horizontal text its will be 1em tall
> and narrower than 1em wide, and in vertical text they will be 1em
> wide and shorter than 1em tall. Right?

So I don't really see the example you're bringing up.  If you're
thinking of a Japanese font that uses non-square kanji characters,
those will be rendered upright in vertical text and thus the same
height in both cases, no?

The 'font-size' property determines the height of glyphs *before*
layout operations. The default rendering of the string "iiiiii" will
render glyphs of the same height in both horizontal and vertical text
runs, only the final orientation will be different when rendered.  Which
one is taller or wider is irrelevant.

You seem to want to describe 'font-size' in terms of how glyphs are
shown on the page after layout operations.  But that's not how any
author thinks about font sizes!  If I have 16px text on the page
that's rotated 45 degrees, I still think of that as 16px text, not as
22.6px sized text, even though that's what the "height" of the text
will be.

Cheers,

John Daggett
Received on Monday, 20 May 2013 10:20:21 UTC

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