60535 - CSS-P absolute positioning vertical offset

Status: RESOLVED INVALID

(Core :: Layout, defect, P3)

Description

[Ben Raubenolt]

While designing a page for class I discovered that absolute positioning of
elements is miscalulated.  Everything that is absolute positioned within another
absolute positioned block container is shifted 16px down from where it should be.

Comment 1

[Alan Shields]

makingtest

Comment 2

[Alan Shields]

Attachment: Minimum test case, with inlined style sheet

Comment 3

[Alan Shields]

testcase

Comment 4

[Boris Zbarsky [:bzbarsky]]

confirming -- I see this with linux trunk build 2000-11-17-08.

Is this a regression?  I believe absolute positioning used to work...

Comment 5

[Ben Raubenolt]

Attachment: Test case with DIV (correct)

Comment 6

[Ben Raubenolt]

Attachment: Test Case with H3 (incorrect)

Comment 7

[Ben Raubenolt]

Absolute positioning does work for DIV, but not for P and H*.  The offset for P
and H* is fine normally and indeed expected.  However, with ablsolute
positioning it should be toggled off.  I would expect the offset problem may
exist with tables as well, but I haven't tested it.

Comment 8

[Boris Zbarsky [:bzbarsky]]

Doh.  The problem here is that the P and H* elements have nonzero margins!  And
absolute positioning specifies the position of the whole box (content, padding,
border, margins), not of the content.  If I set the margin on P to zero on the
original testcase (or if I do the same to H3 in Ben's testcase) the layout is
exactly the same as for divs.  I should have caught this earlier....

Marking invalid, since this is the correct CSS2 behavior.

Comment 9

[Ben Raubenolt]

Boris is right the margins are the problem.  However, this just means there is a
different bug.  My understanding is the there should never be a non-zero default
for margins.  http://www.w3.org/TR/REC-CSS2/box.html#margin-properties  Please
correct me if I'm wrong.  IE 5.5 renders the initial test case correctly with 0
margins as the default.

Comment 10

[Boris Zbarsky [:bzbarsky]]

All that says is that unless the margins are set by a stylesheet they should be
0.  In this case the margins are set by the user-agent stylesheet for HTML 4.0.

If you look at the W3C's recommended HTML 4.0 stylesheet
(http://www.w3.org/TR/REC-CSS2/sample.html), you will see that quite a number of
elements have recommended margins.

Unfortunately, the choice of a user-agent stylesheet is up to the useragent.  So
you really can't depend on the initial values of things like margins and should
set them yourself if you really care about precise positioning....

Comment 11

[Ben Raubenolt]

I stand corrected.  Thank you.  Case closed.

Comment 12

[Mats Palmgren (inactive)]

*** Bug 119342 has been marked as a duplicate of this bug. ***