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Re: [css21] What's the used value of left/right when overconstrained in relpos?

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Mon, 29 Apr 2013 13:32:20 -0700
Message-ID: <CAAWBYDC3CvxPcAhkbDK-d=rT-+go0tShXCJA4nUAQ6G=G5fGkA@mail.gmail.com>
To: Sylvain Galineau <galineau@adobe.com>
Cc: www-style list <www-style@w3.org>
On Mon, Apr 29, 2013 at 1:22 PM, Sylvain Galineau <galineau@adobe.com> wrote:
> On 4/29/13 1:14 PM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote:
>>On Mon, Apr 29, 2013 at 11:38 AM, Sylvain Galineau <galineau@adobe.com>
>>wrote:
>>> Fwiw the old box model module is rather clear about the constraint
>>>fix-up
>>>  applying to the used value in the inline dimensions [1]. As you note,
>>> interop confirms this. I don't think CSS21 or CSSOM ever clearly defined
>>> what getComputedStyle() should return here though.
>>
>>I think you misunderstood my comment about interop.  I was saying the
>>exact opposite - at least three browsers today do *not* apply the
>>constraint fix-up to the used values (or at least, to what
>>getComputedStyle() returns, which is supposed to be the used value).
>
> No I got you right, it's just that I don't quite think of
> getComputedStyle()
> as returning the used value because of the situations where it does return
> the computed value, such as this one. Doesn't really change my point:
> returning the computed value is the interop behavior in this case. Not sure
> this would be a safe change.

Ah, I gotcha.  So you're saying that getComputedStyle should be
returning the computed value.

Here's the problem: Chrome currently does that, but Firefox definitely
resolves percentages (based on layout values) when returning a value
for t/r/b/l in getComputedStyle.  I don't know IE's behavior, since
I'm currently on my Linux box.

So our choices are either:

1. Change CSSOM to remove top/left/bottom/right from the used-value
list, so it joins the rest of CSS in returning computed values
(forcing at least Firefox, and maybe IE, to change behavior for
percentages).
2. Clarify 2.1 that the "ignore" thing has *no effect* on used values;
it just means that the given property has no effect when doing layout.
 t/r/b/l remain as used-values in gCS().  (Requiring Chrome to change
so that it resolves percentages, but we already have an in-flight
patch to do this.)

~TJ
Received on Monday, 29 April 2013 20:33:07 UTC

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