Re: [css3-values] Unit for ideographic advance (ISSUE-195)

On Mon, Oct 31, 2011 at 12:29 PM, Koji Ishii <> wrote:
> This is a follow up to CSS-ISSUE-195[1].
> OpenType spec defines how to calculate Ideographic Em-Box[2]. Historically speaking, East Asian font designers used to use head.unitsPerEm to store this information, so the logic described in the spec falls back to head.unitsPerEm if the information is missing. Authors use "em" units for this purpose today for the same historical reasons, which works for such fonts, but it can be different.
> What we'd like to propose is to make inline-direction length of the Ideographic Em-Box as a unit, so that authors can specify the number of Ideographic Em-Box for lengths such as box width, margins, column width, and column gaps, and so that the value works as authors expect for any fonts.

I'm totally fine with something like this.

>From what I understand, font-specific units are pretty cheap as long
as the information is easily obtainable from the font.  The only thing
I'm somewhat concerned with is an explosion of units, but as long as
they're useful I'm okay with this.

We almost certainly need a nice diagram in the V&U spec to explain the
use of units like this, and figure-height or capital-height.


Received on Thursday, 3 November 2011 17:12:10 UTC