175738 - Parts of a <div> background image isn't drawn in the margin areas of its first block element

Status: RESOLVED INVALID

(Core :: CSS Parsing and Computation, defect)

Description

[Pascal Chevrel:pascalc]

Build 2002101808 WinXP

Steps to reproduce the bug :
1 create a div with a background image and a block element such as a paragraph
or a header :

<div style="position:relative; background:
url(http://bugzilla.mozilla.org/ant.jpg)">
<h1 style="color:red;">text</h1>
</div>

2 create a second div surronded by a border with a background image and a block
element such as a paragraph or a header :

<div style="position:relative; background:
url(http://bugzilla.mozilla.org/ant.jpg)">
<h1 style="color:red;">text</h1>
</div>

expected result :
-apart from the border, the two divs should identical

actual result : a large part of the background image isn't drawn in the first
div, it seems to follow somewhat the top and bottom padding values of <H1>

I will attach a testcase

Comment 1

[Pascal Chevrel:pascalc]

Attachment: testcase

Comment 2

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

Our behavior here is correct.  (Retitling bug to refer to padding rather than
margin, since it makes a big difference.)  The relevant statement in CSS2 that
explain that this behavior is correct are:

  http://www.w3.org/TR/CSS2/box.html#collapsing-margins
     (note that the "and relatively" is an error and should be removed in the
      next draft [W3C internal reference on this change:
      http://lists.w3.org/Archives/Member/w3c-css-wg/2002JulSep/0292.html ])

     "Two or more adjoining vertical margins of block boxes in the normal
      flow collapse."

  http://www.w3.org/TR/CSS2/visudet.html#q17

     "If it has block-level children, it is the distance from the top
      border-edge of the topmost block-level child box, to the bottom
      border-edge of the bottommost block-level child box."

     (There's also a bit of an error here, since it doesn't account for
      cases where there is padding/border on the outer block.)

In other words, all adjacent vertical margins collapse, and when parent/child
margins collapse, the margin ends up outside the parent.

Comment 3

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

Actually, 10.6.3 is already corrected in CSS 2.1 drafts:
  http://www.w3.org/TR/CSS21/visudet.html#q17