298244 - The absolute box is not centered by "margin: auto;"

Status: VERIFIED INVALID

(Core :: Layout: Positioned, defect)

Description

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

CSS 2.1 10.3.7 said:

> If none of the three is 'auto': If both 'margin-left' and 'margin-right' are
'auto', solve the equation under the extra constraint that the two margins get
equal values, unless this would make them negative, in which case when direction
of the containing block is 'ltr' ('rtl'), set 'margin-left' ('margin-right') to
zero and solve for 'margin-right' ('margin-left'). If one of 'margin-left' or
'margin-right' is 'auto', solve the equation for that value. If the values are
over-constrained, ignore the value for 'left' (in case the 'direction' property
of the containing block is 'rtl') or 'right' (in case 'direction' is 'ltr') and
solve for that value.

http://www.w3.org/TR/CSS21/visudet.html#abs-non-replaced-width

But, following testcase is not centered by "margin: auto;".
http://bugzilla.mozilla.gr.jp/attachment.cgi?id=2830&action=view

Comment 1

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Attachment: Patch rv1.0

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(In reply to comment #0)
> > If none of the three is 'auto'

That's the wrong clause, since both 'left' and 'right' are 'auto'.

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Comment on attachment 186806 [details] [diff] [review]
Patch rv1.0

The testcase here is displayed correctly, and this patch makes it incorrect.

Comment 4

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(And we already have code to handle auto margins, and as far as I know that code
is correct.  There's definitely no need to add a second piece of code to do the
same thing.)

Comment 5

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

(In reply to comment #2)
> (In reply to comment #0)
> > > If none of the three is 'auto'
> 
> That's the wrong clause, since both 'left' and 'right' are 'auto'.

Excuse me. I cannot understand well.
Does "If none of the three is 'auto'" mean that the all three values are not 'auto'?
I understood that it means 'left' or 'right' or 'width' is not 'auto'.

Comment 6

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(In reply to comment #5)
> Does "If none of the three is 'auto'" mean that the all three values are not
'auto'?

Yes.

Comment 7

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

O.K. thanks, David.

Comment 8

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

-> v.