- From: Behnam Esfahbod via GitHub <sysbot+gh@w3.org>
- Date: Wed, 15 Feb 2017 09:56:01 +0000
- To: public-css-archive@w3.org
@frivoal, I just posted a summary of our discussion last week here: https://github.com/w3c/alreq/issues/86#issuecomment-279963613 > We discussed underline/overline methods on the 7 February 2017 weekly meeting. > > Here's a summary: > > 1) Existing practices (meaning almost any handwriting, lithography, movable type, and traditional word processors) puts underline/overline below/above all glyph parts (letter parts and diacritics). Therefore, this is a desired behavior. > > 2) We will keep looking for other practices and will document when we have good evidence. > > 3) Based on the samples collected, looks like implementations need to find a better way of calculating a position for underline/overline based on font data. Most probably, it will use ascend and descend values for the positioning. > > 4) In any case, if the underline/overline collides with ink, the prefferred default behavior would be to skip the ink. > > 5) When skipping ink, it's also preferred to make sure the underline/overline drawing does NOT form a short pieces, which could be easily mistaken with dots or diacratics. To prevent this, the drawing can be skipped for parts with a short width. So, to answer to your questions, > the ideal behavior for Arabic and other languages using the same script is to position the underline so that it does not intersect, making the question of whether or not to skip irrelevant since there is no intersection. Exactly! > The position of the underline is controlled by https://drafts.csswg.org/css-text-decor-4/#underline-offset, and the default value allows for that. It should probably be clarified to make sure that it not only allows for it, but actually requires it, or if we cannot do that, at least recommend it. IMHO, the `text-underline-*` properties are designed with only Latin-similar writing systems in mind, assuming there's a baseline and letters sit on top of that, which is not a valid assumption for Arabic scripts. If we really want to expand control over the underline/overline behavior, we should start with allowing positioning based on any of baseline, ascend, descend, and possibly other font properties. Having only two positioning options (`under` and `over`) and then manually moving the lines with an `offset` doesn't sound like a user-friendly alternate. > Some (many) current implementations may be doing a terrible job of implementing auto correctly, and place the underline in a way that does intersect. We can hope this will go away eventually, but maybe it will take a while, and maybe there are cases where that is not possible. Yes, unfortunately. > Also, it remains possible to place the underline manually, and make it intersect. > > When that happens, what should we do if the author has not said what they want in terms of ink skipping. skip by default or not? > > It seems to me that although avoiding intersections is the main goal, if intersections do happen, skipping ink is better than not. Does that make sense? Yes, skipping in any case of collision would be a wise choice. -- GitHub Notification of comment by behnam Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/727#issuecomment-279966408 using your GitHub account
Received on Wednesday, 15 February 2017 09:56:08 UTC