- From: Koji Ishii <kojiishi@gmail.com>
- Date: Sat, 24 Jan 2015 17:03:22 +0900
- To: Bobby Tung <bobbytung@wanderer.tw>
- Cc: Xidorn Quan <quanxunzhen@gmail.com>, www-style list <www-style@w3.org>, CJK discussion <public-i18n-cjk@w3.org>
I had an impression that someone has solved somehow and Bobby knows that, because WebKit has implemented inter-character already. It's a bit unfortunate to know that this wasn't solved yet. I agree with Xidorn that this should be solved outside of the ruby spec. So, both of you know the spec/algorithm to layout Bopomofo tonemarks? I suspect still-in-work CLREQ might cover that, but if there was a polyfill on github, that'd be a great first step. It helps authors, and it may help possible contributors with font knowledge to understand the necessary spec/algorithm. /koji On Fri, Jan 16, 2015 at 10:11 AM, Bobby Tung <bobbytung@wanderer.tw> wrote: > Hi Xidorn, > > I remember this issue is discussed in TPAC 2014 ruby session. Layout Engine > and fonts' GPOS are ok for the tone marks. > > But fonts vary and may take longer for penetration. I'd like to hear more > comments from implement side for the issue. > > WANDERER Bobby Tung > Sent from my iPhone. > > Xidorn Quan <quanxunzhen@gmail.com> 於 2015年1月16日 上午8:38 寫道: > > Hi, > > The current CSS Ruby spec requires UAs to position the tone marks in ruby > annotation properly in the note below "ruby-position: inter-character;" [1] > and I was trying to implement this during the last few days. But it then > makes me wonder whether it is worth to implement this in layout engine. > > The first reason made me think about this was the fact told by Bobby that > the tone marks are always positioned in a separate column for vertical > bopomofo in all contexts, not only when they are inside ruby annotation. > Which means, the tone mark positioning is not limited to inter-character > ruby; it also covers ruby and non-ruby text in vertical text. It is > definitely what fonts should handle. > > The other potential problem for this is that, it will never be interoperable > until all UAs implement this in the same way. There are a lot of details > need to be considered, for example, what tone marks should be repositioned? > Only trailing ones, or every one? What exactly position the tone mark should > be placed when font or font size vary? It would be hard for author to detect > whether a UA support the tone mark positioning, and how it is implemented. > > In conclusion, I don't think it is a good idea to implement tone mark > positioning in layout engine. It would affect interoperability and > complicate the impls. The positioning should be handled by fonts. > > However, we know that no fonts seem to support this currently. They even > display a rotated tone mark in vertical text. For this, I suggest we use > polyfiller to do the positioning. It would be easier to implement this in > JavaScript and DOM, a polyfiller also provides more flexiblilty for authors > to control over the behavior. Once the fonts start supporting this, authors > can simply remove the polyfiller. > > The attachment is a simple polyfill demo for tone mark positioning. It seems > to work almost fine with Trident and WebKit (with a little problem with > Gecko, though, because of the incomplete ruby impl) > > - Xidorn > > [1]: http://dev.w3.org/csswg/css-ruby/#valdef-ruby-position-inter-character > > <tone-mark-positioning.html>
Received on Saturday, 24 January 2015 08:03:54 UTC