RE: [css3-text] scoping line break controls, characters that disappear at the end of lines

I asked this question for ideographic spaces at public-html-ig-jp@w3.org in January without good conclusion at that point. I then had some discussion with fantasai, investigated a little more, and came into diffident conclusion than before.

In short, I support the current spec--keep around all those fixed-width spaces.

Long version: fantasai helped me to make the question simpler:
A. If it occurs at the beginning of a line, does it take up space?
B. If it occurs at the end of a line, does it take up space?
C. If there is more than one together, are they kept together, or can we break between them?

By eliminating logically incorrect combinations and incorporating opinions from Japan, we have 3 options:
1. YES on the beginning, NO on the end, and keep consecutive spaces together.
2. YES on the beginning, YES on the end of line, and allow break between them.
3. Variation of 1; allow only one ideographic space at the end, and ignore the rest.

MS Word behaves #1. Most traditional Japanese word processors in 1980/90s behaved #2. #3 is from JLTF, where he likes Word's behavior except that an ideographic space after an exclamation or question mark should be honored.

I quickly looked at current behaviors[1]:
MS Word: #1
Adobe InDesign: #2
IE9: #1
FF11: Neither. Breaks look like IE, but the last two are different. Justification behavior is also different.
Chrome18/Safari5: #2

MS Word took #1 because in 1990s, many Japanese authors used ideographic spaces and ASCII spaces mixed without understanding so. Oftentimes they do so intentionally assuming two ASCII spaces are equivalent to one ideographic space, because it was so in most traditional CUI-based software. To handle two ASCII spaces and one ideographic space in the same way, and also to support Latin typography, #1 was the best choice.

Today, in HTML world, I don't think Japanese authors have such requirements, so there's no big motivation to take the #1 for CSS.

The point JLTF made--an ideographic space after exclamation/question marks--makes sense, but it's too special case once we took #1, so Word gave up implementing it. But it's free of cost if we go with #2.

Give this, given InDesign taking option 2, and given all browsers behaving differently today, I think option 2 makes the most sense.

Note that this is filed as CSS-ISSUE-220[2].

[1] http://lists.w3.org/Archives/Public/www-archive/2012Mar/0058.html
[2] http://www.w3.org/Style/CSS/Tracker/issues/220

Regards,
Koji

-----Original Message-----
From: fantasai [mailto:fantasai.lists@inkedblade.net] 
Sent: Tuesday, January 10, 2012 10:37 AM
To: www-style@w3.org; 'WWW International'
Subject: [css3-text] scoping line break controls, characters that disappear at the end of lines

In 2008 roc outlined some principles for how line breaking controls (i.e. 'white-space', at the time) are scoped to line-breaking opportunities:

In <http://lists.w3.org/Archives/Public/www-style/2008Dec/0043.html> Robert O'Callahan wrote:
>
> 1) Break opportunities induced by white space are entirely governed by the
>    value of the 'white-space' property on the enclosing element. So, spaces
>    that are white-space:nowrap never create break opportunities.
> 2) When a break opportunity exists between two non-white-space
>    characters, e.g. between two Kanji characters, we consult the value of
>    'white-space' for the nearest common ancestor element of the two characters
>    to decide if the break is allowed.

I'm trying to encode this into the spec. My question is, are spaces (U+0020) the only characters that fall into category #1? What about the other characters in General Category Zs?
   http://www.fileformat.info/info/unicode/category/Zs/list.htm

In particular, U+1680 is, like U+0020, expected to disappear at the end of a line.

Which brings up another issue: which characters should disappear at the end of a line? Right now we keep around all those fixed-width spaces.

~fantasai

Received on Saturday, 31 March 2012 20:11:03 UTC