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Re: [csswg-drafts] [css-rhythm-1] Avoiding accidental double spacing

From: Koji Ishii via GitHub <sysbot+gh@w3.org>
Date: Thu, 26 Jan 2017 18:32:32 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-275470960-1485455550-sysbot+gh@w3.org>
Since I wasn't able to express my points very well in the weekly conf 
call, let me continue my points here by cc'ing people who spoke at the
 weekly on 25 Jan, from [IRC 
log](https://log.csswg.org/irc.w3.org/css/2017-01-25/#e766245):
@astearns @stevezilles @tantek @tabatkins @dbaron @fantasai @dauwhe 
@litherum @FremyCompany 
There were some points what I said didn't seem to be understood 
correctly, or I didn't understand even by reading IRC log, so 
appreciate to read through and comment here if any.

`line-height: normal` doesn't produce a robust layout as discussed, 
and I agree that a robust layout is one of important principle in CSS,
 and that `line-height: normal` is against that.

The purpose of `line-height: normal` is different; it is designed to 
avoid line overlaps as much as possible. Making any text readable 
without unexpected overlaps is also one of important principles in 
CSS. These two important principles conflict to each other. I think 
that is why `line-height` gives a choice to authors, and I think CSS 
chose the right default because overlapping is worse problem.

What I was trying to say at the weekly was that we need to give the 
choice to authors regardless rhythmic sizing is used or not, and IIUC 
this is also what @litherum was trying to say.

I made [a multi-script sample text here](http://jsbin.com/xekuhu) 
(credits to @r12a and @aphillips, thank you!) For scripts in this 
example, I hope you see `normal` works perfectly in all browsers, but 
if we were to pick one fixed value, probably "1.8" is a good value. 
But I saw an example where "1.8" wasn't still tall enough before. Pick
 "2"? But it's too tall for some other scripts, such as Latin.

Or, maybe, I wonder, from @fantasai's comment above, this point was 
understood but cases where font metrics-based line height and rhythmic
 sizing used together was not understood?

If that's the case, I'm quite sure this case is common; author wants a
 constant rhythm, such as 18pt. The page has CGM that text can be in 
various scripts. Author wants to prioritize "lines not to overlap" 
over "possible additional space when falls back to bad fonts occurs," 
because font fallback is more predictable than CGM text content. In 
this case, the combination of `normal` and rhythmic sizing is what the
 author needs.

If the author uses `line-height: normal`, Latin lines will fit to one 
step unit, while Tibetan may fit to two or three step units, but still
 the rhythm is kept.

...or maybe concerns discussed there was different from either of 
above, appreciate if someone can explain more if so.

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Received on Thursday, 26 January 2017 18:32:38 UTC

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