Re: [css-values][css-writing-modes] ch and ic units

On Sun, Mar 6, 2016 at 7:00 PM, Florian Rivoal <florian@rivoal.net> wrote:

>
> 2) "advance measure", as used in the definition of both the ch and ic
> units isn't defined, and we need to clarify how it works in vertical
> writing modes. Since they are typically used to set the inline size of
> something in terms of a number of characters, it would makes sense to me in
> - in "writing-mode:sideways-*" or
> "writing-mode:vertical-*;"text-orientation:sideways", advance measure for
> both units means advance width
> - in text-orientation:upright, advance measure for both units means
> advance height
> - in text-orientation:mixed, ch should use the advance width, which ic
> should use the advance height.
>

For CJK authors, "ch" is quite useful to get the approximate width of
non-CJK characters, and in CJK vertical flow, the height is almost 1em.

With your proposal, authors will lose a way to get the former, and makes
"ch" equivalent to "em" except for very few exceptional fonts.

I prefer "ch" always be the "width of "0" glyph, or 0.5em" as what authors
lose looks more than what authors get.

/koji