Bug 19149 – A position fixed node's offsetParent should return null

• Component: DOM
• Status: RESOLVED FIXED

[Gérard Talbot (no longer involved)]

CSSOM View Module, offsetParent attribute clearly states that 
offsetParent of nodeA when nodeA is a position: fixed element should return
null.

"
If any of the following holds true return null and stop this algorithm:
(...)
    The computed value of the position property for element A is fixed. 
"
http://www.w3.org/TR/cssom-view/#offset-attributes

Steps to reproduce:
1- Load provided URL
2- Click the [return document.getElementById("PositionFixedElem").offsetParent]
button

Actual results in Safari 3.1.1 build 525.17.0 under XP Pro SP3:
document.getElementById("PositionFixedElem").offsetParent = [object
HTMLBodyElement]

Expected results:
document.getElementById("PositionFixedElem").offsetParent = null

Notes:
- Internet Explorer 7, Internet Explorer 8 beta 1 and Opera 9.50 will return
null.
- I have filed a similar bug at
https://bugzilla.mozilla.org/show_bug.cgi?id=434678

I have searched for a duplicate and did not find one. 
I have not checked the testcase with a webkit trunk nightly build (526+).

I'm seeing this too. WebKit nightly from 13 Jan 2009, OS X 10.5.6.

[Matt Pennig]

<rdar://problem/6497927>

[Matt Pennig]

Created attachment 26829 [details]
Fix for offsetParent, offsetTop, and offsetLeft

[Matt Pennig]

Created attachment 26834 [details]
Fix for offsetParent, offsetTop, and offsetLeft

[Anthony Ricaud]

The testcase is working on my nightly (r41121). I've bisected it between r40738 and r40771. http://trac.webkit.org/changeset/40769 may be the revision responsible (I don't understand the patch but it has offsetParent in the summary).

Bug 24097 was fixed as a regression because of this change. One of them is therefore invalid.

[Matt Pennig]

This bug was fixed in changeset http://trac.webkit.org/changeset/40769 but there were no tests to make sure that offsetParent of a fixed element was null. Bug 24107 fixes a related issue caused by the above changeset. In the included patch, there are a number of tests which have coverage on this bug.

[Gérard Talbot (no longer involved)]

When I try the provided testcase with latest stable release Safari 4.0 build 530.17, I get expected results.

Resolving as FIXED

Thank you Matt!

regards, Gérard