- From: Koji Ishii <kojiishi@gmail.com>
- Date: Fri, 11 Mar 2016 16:55:27 +0900
- To: fantasai <fantasai.lists@inkedblade.net>
- Cc: "www-style@w3.org" <www-style@w3.org>
- Message-ID: <CAN9ydbV05GOYkyLOfMFgjpBbmKTZN0QxOTW2MteqjU8UPc5nPw@mail.gmail.com>
On Fri, Mar 11, 2016 at 6:14 AM, fantasai <fantasai.lists@inkedblade.net> wrote: > On 03/09/2016 11:07 PM, Koji Ishii wrote: > >> On Thu, Mar 10, 2016 at 6:36 AM, fantasai wrote: >> > >> > * We have an en unit. It does not change per writing mode. >> >> Where is it defined? I can't find in CSS Values[1]? >> > > Sorry, my mistake. I was mixing up with "ex" unit. "ex" is x-height, it's not a width... > > * The use case for ch is an exact (for monospace fonts) or >> > approximate (for proportional fonts) sizing function >> > with respect to the number of characters that can fit on >> > a line. Its primary use case is <textarea>, <input>, and >> > <pre>. Ignoring the effects of text-orientation here would >> > make it fail at its primary use case. >> >> Doing so doesn't solve what you want to solve, since it only solves for >> digits. >> > > It does solve it exactly for monospace fonts, and for tabular > digits, and in fully proportional cases it's as close of an > approximation as you can get. It's the best we can do, and > it's needed to make the 'width' attribute of these elements > work correctly. All alphabets are likely to be proportional heights even for monospace fonts. We intentionally left sythesizing height algorithm undefined IIRC, Currently, WebKit/Blink on Mac synthesize it from bounding box, so "i" has smaller advance than "k". Blink on Windows and Gecko uses A+D for the advance of upright, but I've got feedback from web authors that this is a bad behavior, so we might change. That said, there's no monospace upright fonts. > Fwiw, the ch unit is already defined to be writing-mode sensitive, >> > as the spec very intentionally uses the term "advance measure" and >> > not "advance width". >> >> >> I wasn't aware of that, if so, I'd request to change. This is too >> bad for authors, and makes things unnecessarily complex. >> > > I've given the use cases for ch as defined in the spec. > You still haven't given me a use case for ch as you prefer it defined. Given above, I don't think it's a valid interoperable use case. My use case is listed above; authors need something like "en". > Not quite. A font with proper vertical metrics will not use >> > a full em for the advance height of its ASCII characters. >> >> And such fonts will not work with the "ch" definition you're >> proposing except for monospace digits. The solution is too >> restrictive and makes little sense to me. >> > > I don't see how your proposed definition improves anything. It keeps "ch" constant, regardless of text-orientation, and that's what I understand web authors want. /koji
Received on Friday, 11 March 2016 07:56:15 UTC