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RE: [css3-images] 2011/12/01 ED section 4.2 review notes

From: Brian Manthos <brianman@microsoft.com>
Date: Thu, 1 Dec 2011 22:01:21 +0000
To: Tab Atkins Jr. <jackalmage@gmail.com>
CC: fantasai <fantasai.lists@inkedblade.net>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <9710FCC2E88860489239BE0308AC5D170450C648@TK5EX14MBXC264.redmond.corp.microsoft.com>
>> # radial gradient is specified by first pinpointing the center
>> # of the gradient (where the 0% ellipse will be) then specifying
>> # the size and shape of the ending shape (the 100% ellipse).
>> 1. The prose doesn't align with the grammar like it used to.
>> In the previous grammars, this prose aligned with the ordering in the grammar...
>>        ... (<position>, <size-shape>, <colors>)
>> I think it's worth considering updating the prose to match the new grammar ordering.

> Fixed.  "A radial gradient is specified by indicating the center of
> the gradient (where the 0% ellipse will be) and the size and shape of
> the <dfn>ending shape</dfn> (the 100% ellipse)."

That doesn't address the issue.  Your new text has the form...
	"A radial gradient .... [position information] .... and [size and shape information] ..."
whereas the grammar has it in the opposite order.

>> 2. Position can no longer be first.
>> In the prior WD grammar, position was always first.  In the ED grammar prior to 12/28, position *could* be first.  With the current ED grammar it can never be first.
>It could only be first if you omitted the shape, and only because the
>shape and size weren't connected.


WD 2011/09/08

<radial-gradient> = radial-gradient(
		[<shape> || <size>]
		[<length> | <percentage>]{2}
	<color-stop>[, <color-stop>]+
radial-gradient(5px 6px, 7px 8px, red, blue)

ED 2011/11/11

<radial-gradient> = radial-gradient(
  [ <shape> , |
    <shape>? [ at <position> || to <extent> ] ,
  <color-stop> [ , <color-stop> ]+
radial-gradient(at 5px 6px to 7px 8px, red, blue)

Both old grammars allowed position to go first *with explicit sizing present*.  The new grammar does not.

> It can still be "first" if you omit the size and shape entirely.

In the irrelevant case where only 1 is specified perhaps.  But that’s sidestepping the actual concern.  "I won the nomination as the only candidate in the primary."

> The possible orderings don't seem significant to me.

And you might be fine with that, but it's a change that wasn't discussed and I think it's a bad idea relative to where we were (mid-November ED).

I would prefer either we allow full reordering (and we can, without ambiguity) or no reordering.  A partially flexible parser just confuses people rather than helps them.

>> 3. The meaning and rendering of "simple two length/percent" radial gradients has changed.
>On the other hand, the November ED made just-a-size-keyword and
>just-a-size-and-shape-keyword invalid, while the December ED returns
>it to validity with the same meaning as the previous WD.  Kind of a
>toss-up in terms of what different grammars allowed, I think.

I think it's the wrong choice and found it worth calling out because it feels *just like the angle coordinate system* change where the same-syntax-means-something-different is a bad thing -- and I agreed with Brad on that concern then and now.

>> 4. circle/ellipse keyword can now be repositioned
>It's still prevented from coming after the "at <position>", though,
>for the same reasoning as before.

This is a better explanation for change #2 above.  I might be able to get on board with that but need to think about it some more.

>> 5. Editorial snafu with <position> prose regarding "defined".
> I think you're misunderstanding that comment - it's not "the entire
> syntax of background-position", but it *is* defined by the
> background-position syntax, as that syntax has a <position>
> non-terminal.

Can we add "a single layer of" in front of 'background-position' to avoid the confusion?

# The <position> notation is defined by the positioning syntax of ‘background-position’ and is resolved in the same way

# The <position> notation is defined by the positioning syntax of a single layer of ‘background-position’ and is resolved in the same way

>> 6. Editorial snafu with <position> prose regarding "box".
> ... I've now defined the term "gradient box" ...
Sounds like a good change, I'll follow-up separately if I find new concerns on this one.

>> 7. "Similar to" is the proper phrasing for the prose within 'farthest-side' and 'farthest-corner'.
> I find your "absurd" statement perfectly reasonable, too.  ^_^
Agree to disagree all the way to REC.

> > # <extent-keyword> = closest-corner | closest-side | farthest-corner | farthest-side
> > 10. To my recollection, we did not have consensus on the official demise of "cover" and "contain".  Did we resolve on that?  If not, it might be worth adding an issue near "<extent-keyword>" to call that out.
> Are you asking for an issue because you disagree, or just for
> completeness?  If the latter, I don't think we need to call it out
> specially.

Completeness and clarity for authors and implementers.

For example, when adding/updating my implementation for the new grammar should I remove cover and contain under the assumption that they are gone OR should I leave them in place until we have are resolution?  For the moment, my gut is "do the least work" until I know more.

I'm undecided on whether to keep them or not.  I see merit in both options.
Received on Thursday, 1 December 2011 22:02:02 UTC

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