W3C home > Mailing lists > Public > www-style@w3.org > October 2011

Re: List cases for a cap height unit

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 26 Oct 2011 11:34:28 -0700
Message-ID: <CAAWBYDDbbd65hSr6FmqRg6S4RRSRx+kRwND34fWdyLOwr+b9rw@mail.gmail.com>
To: Alan Stearns <stearns@adobe.com>
Cc: www-style list <www-style@w3.org>
On Wed, Oct 26, 2011 at 11:01 AM, Alan Stearns <stearns@adobe.com> wrote:
> On 10/26/11 10:36 AM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote:
>> On Wed, Oct 26, 2011 at 10:13 AM, Alan Stearns <stearns@adobe.com> wrote:
>>> It all depends on the font. In some fonts ascent will be significantly
>>> taller than cap height, so a lowercase 'f' will loom above a capital "A."
>>> What "size of the text" means is a little fuzzy - is it cap height, ascent,
>>> the max of those, or an optic average?
>> For use case 1, "size of the text" means "a normal height for a
>> capital letter, so it blends in typographically".  For use-cases 2 and
>> 3, it means "the largest height such that, when the image is placed on
>> the baseline, it doesn't change the line's height".
>> I *think* that cap height works for both of these definitions.  Am I wrong?
> I think cap height works fine for all of the use cases (not necessarily the
> definitions, see next para). My point is that using the term "cap height" in
> the use case makes the language more precise, and less open to
> misinterpretation. I don't want someone to read "as tall as possible" and be
> disappointed that they get something slightly less tall than it could have
> been.

In the final property descriptions, of course precise terms will be used.

In use-cases, you rarely need or want that, because you're looking for
problems to solve, not solutions.  Using the cap height or the ascent
or what have you is part of a particular solution to a use-case.

> Your "largest height such that..." definition above does not match cap
> height (since ascent can be larger). The use cases work perfectly fine with
> cap height, and cap height is guaranteed not to increase the line's height.
> It's just not always going to be the largest height that does not increase
> the line's height.

Ah, I didn't realize that.  (Can you tell I'm not a font geek?)  After
doing some reading, both of yours and Steve's messages and some other
pages on the net, it looks like cap height is still what is wanted for
usecases 2 and 3.  More generally, for both of them you want a height
that "fills the line" without disturbing the vertical rhythm.  A
sparkline that went from the baseline to the ascent would be slightly
suboptimal, as it would be taller than most capital letters and thus
would "stick out" somewhat.  Similarly for smilies - I believe one
that went up to the ascent would look a little bit oversized.

On Wed, Oct 26, 2011 at 11:10 AM, Stephen Zilles <szilles@adobe.com> wrote:
> For your example of a new math sign, of course the figure height (usually
> slightly less than the cap height) would make more sense.

What's the figure height?  From what I can glean from the internet, it
appears to be the height of numbers?  That's not necessarily what you
want - for example, if we pretended that the forall symbol wasn't in
Unicode and you were providing it as an image, you'd want it to be the
height of a capital letter.

So, signs/operators/etc in math or logic may want to be either the cap
or figure height, depending on intended usage.

> In a Middle Eastern context (i.e. unicameral "alphabets" - Arabic, Armenian,
> Coptic/Ethiopic, and Hebrew) I would suggest using the figure height -
> although there's a risk that figures in many fonts for these systems will
> not be well fitted to the design.

Can you point to a diagram or something similar showing the
differences between figure and cap height for such scripts?  I don't
have a good graph on why one is better than the other for these types
of scripts.

Received on Wednesday, 26 October 2011 18:35:18 UTC

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