76726 - centered table caption is not bounded by left side of container on overflow.

Status: VERIFIED FIXED

(Core :: Layout: Tables, defect)

Description

[Alexey Chernyak]

OS: Win2K
Build: 2001041804

when a centered caption width is bigger than width of it's container it is not
bounded by container's left side and gets misaligned with table.

Comment 1

[Alexey Chernyak]

Attachment: testcase

Comment 2

[Alexey Chernyak]

Attachment: screenshot

Comment 3

[Alexey Chernyak]

CCing Bernd Mielke
maybe he knows how to fix this.

Comment 4

[Bernd]

steeling the bug

Comment 5

[Bernd]

Attachment: patch

Comment 6

[Bernd]

The patch passes the regression tests.

Comment 7

[karnaze (gone)]

r=karnaze

Comment 8

[Chris Waterson]

This patch seems reasonable if the behavior is appropriate. Ought the caption's
width be pinned to the width of the containing block, instead? cc'ing hixie, who
might have an opinion.

Comment 9

[Hixie (not reading bugmail)]

I doubt that is a complete fix, but I guess it's an improvement of sorts. For a
complete discussion on the way captions are _supposed_ to work, see:
   http://www.w3.org/TR/REC-CSS2/tables.html#q5

Comment 10

[Alexey Chernyak]

Quoting CSS2 spec: "A caption that is above or below a table box also behaves
like a block box for width calculations; the width is computed with respect to
the width of the table box's containing block."

In the testcase the caption has explicitly specified width through CSS.

I think shrinking down width of a block, which has it explicitly specified, to
the width of containing block is wrong?
That's what Ian been teaching us anyways in his Evil horisontal growth tests.

Comment 11

[Alexey Chernyak]

Attachment: testcase with block elements added

Comment 12

[Alexey Chernyak]

What's interesting in the testcase added above, the left border of the contained
<div> elements seems to be collapsed? Also although specified <div> and <table>
widths are the same, for some reason <div> appears longer than <table>?

Now that one beats me.
I'm using win32 build 2001081208

Comment 13

[Bernd]

Chris, the caption - inner table widths magics are at
http://lxr.mozilla.org/mozilla/source/layout/html/table/src/nsTableOuterFrame.cpp#1500

The patch solely removes computation of the negative margins and are in my
oppinion the right thing in order to get table and caption moving together as
required by the spec.

>I doubt that is a complete fix, but I guess it's an improvement of sorts. For 
>a complete discussion on the way captions are _supposed_ to work, see:
>   http://www.w3.org/TR/REC-CSS2/tables.html#q5
IMHO, this is a complete fix for this particular bug. This is ground work for
bug 3166. A simple querry shows that we have currently 9 bugs with caption in
the subject, I can't fix them all at once :-(. BTW, I disagree that the css spec
provides a complete discussion, bug 60365 may be just an example of the problems
with the spec especially when combined with html4.

Hixie, could you be less vague and give a clear statement: should the caption
shrink or not to the containing block width? Your vague statement seems to me
blocks the sr  and my checkin (and I doubt that the tree will become greener
than it is now ;-))

Comment 14

[Alexey Chernyak]

Attachment: same as above but with dir="rtl"

Comment 15

[Alexey Chernyak]

The above testcase is even more bizzare and beats me. Ian might have idea of
what's happening there and how many bugs it uncovers. Both testcases validate as
HTML 4.01 Strict.

Either way, Bernd, I think your patch should work for the caption in the above
testcase as well? Could you check just in case? :o)

Comment 16

[Bernd]

Attachment: rtl rendering with patch

Comment 17

[Hixie (not reading bugmail)]

Bernd: Basically, the table element generates an anonymous box that contains 
the table box itself and the caption's box. The table and caption boxes retain 
their own content, padding, margin, and border areas, and the dimensions of the 
rectangular anonymous box are the smallest required to contain both. Vertical 
margins collapse where the table box and caption box touch. A caption that is 
above or below a table box also behaves like a block box for width calculations;
the width is computed with respect to the width of the table box's containing 
block (which is the anonymous box I mentioned above).

So the outer size of the caption, assuming it has width set to 'auto', will be 
the outer size of the table (by 'outer size' I mean margin-edge to margin-edge).

The difference in our handling of overflow for rtl vs ltr is a bug in block code
(the tables are doing it right). I think.

Comment 18

[Bernd]

So the outer size of the caption, assuming it has width set to 'auto', will be 
the outer size of the table (by 'outer size' I mean margin-edge to margin-edge)

 Hixie really?: 
<body>
<table style="margin-left:auto; margin-right:auto"> 
<caption>

will then the caption be as wide as the page - minus body margins?

Comment 19

[Hixie (not reading bugmail)]

No, because the box that contains the table and caption will be the smallest
possible to contain both, which will be exactly the intrinsic width of the 
table, since 'auto' margins can be pushed down to zero.

  +-----------------------+
  |+---------------------+|
  || caption             ||
  |+---------------------+|
  |+---------------------+|
  || table               ||
  ||                     ||
  |+---------------------+|
  +-----------------------+

This is a contradiction in the spec, though, since the non-normative example a 
bit lower down relies on the opposite behaviour.

Comment 20

[Alexey Chernyak]

can we get sr please?
the patch does the job of fixing this particular bug and does display the right
behaviour.

Comment 21

[Bernd]

yeah, I should have asked you for this :-). The box size issue described by
Hixie is the central issue in bug 60365, which is also assigned to me, so it
will not get lost.

Comment 22

[Alexey Chernyak]

Bernd, this has nothing to do with align attribute or centering, this is about
overflow behaviour. I think you just confused these 2 bugs and changed bug
fields by mistake. I'm reversing them to previous state.

I'm sorry my testcases uncover other unrelated bugs with block elements, and
this gets sidetracked.

But as far as this particular bug, it's testcase and the caption element in it
are concerned:

1. Both table and caption do center correctly through CSS. So it's not a matter
of centering.
2. Both table and caption are given explicit width through CSS and both abide
it. No problem there either.
3. Caption horisontal overflow behaviour was erroneous and the patch fixes it.

Ian said tables are displaying correct behaviour with the patch.

Comment 23

[Chris Waterson]

sr=waterson

Comment 24

[Bernd]

Thanks Alexey for restoring the bug status, this was a mozilla bug corrupting
the data fields when more then one bugzilla window is open. Seems that I should
upgrade...

Comment 25

[Bernd]

fix checked in, bug 96394 has the remaining block issue.

Comment 26

[Alexey Chernyak]

verified

Comment 27

[Alexey Chernyak]

Bugs have been filed for other issues that my last testcase has uncovered, here
they are:
bug 96394
bug 96463
bug 96655
bug 96658
bug 96670