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Re: font size: proposed plan

From: Erik van der Poel <erik@netscape.com>
Date: Fri, 28 Jan 2000 07:09:35 -0800
Message-ID: <3891B12F.DD8B9AA8@netscape.com>
To: www-style@w3.org
My recent messages to this list may give the impression that I have
dropped *all* of my font-related suggestions for the CSS spec. That is
not true at all.

I have dropped my suggestion to change the definition of "em" to be the
width of M, and I have dropped my suggestion to try to take into account
fonts with accents inside their em square (the fonts Kent mentioned).

But I have *not* dropped the following:

1. "em" needs to be clarified to say whether it means the computed or
actual value of font-size. And whether it refers to the first available
font, or the height of the text in the element, since it may require the
use of more than one font in the font-family list (plus UA fallbacks).

2. "font-size" needs to be clarified to say what it really means. I
don't know whether it would be wise to actually mention terms like "em
square" in the font-size definition since CSS is for various media
types, not just the screen. However, I have often found that it is
useful for a spec to have both "normative" and "informative" parts,
where the normative spec gives you a very terse and sometimes
intentionally vague or flexible definition, while the informative part
(e.g. appendix) gives some background info for implementors, rationale,
etc. Would it be useful to have such an informative appendix, where we
discuss Windows's negative lfHeight in LOGFONT, X Windows issues,
TrueType's em, etc?

3. Font box model. Since the font-family property allows multiple fonts
to be specified (and since the font matching algorithm allows the UA to
use a UA-dependent fallback anyway), we need to come up with some sort
of "font box" model that describes how the individual fonts are aligned
vertically in the context of line box, inline box, vertical-align,
line-height, etc.

4. Change the words "leading" and "half-leading" to something more
appropriate e.g. line spacing.

5. Clarify the half-leading stuff. It currently has some vague wording.
We need to clarify whether the half-leading needs to be added above and
below the em square (as opposed to the font's bounding box).

---

That's it for now.

Erik
Received on Friday, 28 January 2000 10:12:07 GMT

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