Re: [css-text-decor] Doesn't example 3 in text-underline-position break current UA behavior?

Revisiting this thread after 6 months since last reply gave me a slightly
fresh view.

On Fri, Jul 3, 2015 at 2:12 AM, Myles C. Maxfield <mmaxfield@apple.com>
wrote:

>
> I'm proposing that "auto" should take any and all context into
> consideration, including things like which language the text seems to have
> come from, how many characters in a row seem to come from that language,
> where line breaks occur, etc. Given all this information, "auto" can decide
> whether to put the line on the left or the right, and it can make this
> decision on whatever granularity makes the most sense (character, phrase,
> line, element, etc.). I'm also proposing that this behavior be able to be
> overridden using "under", "left", or "right".
>
> "auto" would mean "Do whatever you think is best"
>

I still agree on this. For this to work, we need two edits to the spec:
1. Remove the UA stylesheet rules and let UA to figure out whatever if
"auto".
2. Remove "however it must be placed at or under the alphabetic baseline"
from "auto" since it prohibits placing on right in vertical flow.


> "auto left" would mean "For vertical writing modes, put the underline on
> the left. Otherwise, it's up to you."
>

Logically I agree, but in reality, I can't come up with any case this
combination is useful. "left" means either accounting or Chinese, and
"right" means either Japanese or Korean, so "left" or "right" implying
"under" looks reasonable to me.


> "under left" would mean "For horizontal writing modes, use the 'under'
> underline. Otherwise, (for vertical writing modes), put the underline on
> the left"
>

I agree on this, and this is the same as in the spec.


> "under" would mean "For horizontal writing modes, use the 'under'
> underline. Otherwise, do whatever you think is best"
>

I agree on this. "right" and "left" can imply "under", but the opposite
isn't true; "under" could be "left" (accounting or Chinese) or "right"
(Japanese or Korean.)


> "left" is the same as "auto left"
>

See above, the same as "auto left".

So now my proposal is above 1 and 2, and:
3. Clarify when "under" alone is used, its position in vertical flow is
automatic (the behavior isn't defined today.)
4. The value syntax could be one of:
  a. No change: auto | [ under || [ left | right ] ]
  b. Full options: auto | [ under || [ left | right | auto ]]
  c. Simpler: auto | under | left | right

I prefer "simple and good enough for now, extend in future" option, so "c".

/koji