Bugzilla

I have slightly edited the test to meet the current version of the spec.

CSSOM View Module
W3C Working Draft, 17 March 2016
7. Extensions to the HTMLElement Interface
https://www.w3.org/TR/cssom-view-1/#dom-htmlelement-offsetparent

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(In reply to Jaroslav Zaruba from comment #3)

> Obviously this also means that there is currently no way to compute actual
> offset (position) of an elment with position:fixed.

Correct.

> offsetTop:
> "If the offsetParent of element A is null or the HTML body element return
> the distance, as number of CSS pixels, between the top border edge of
> element A and the canvas origin and stop this algorithm."
> 
> Currently the offsetTop property of position:fixed element always contains 0.

In a test page, I am able to get the offsetTop property of a 'position: fixed' element (which is not 0) with Firefox 47 and Chrome 51. But the spec says it should not be possible since offsetParent of a 'position: fixed' element should be null.

Current version of the spec.:

CSSOM View Module
W3C Working Draft, 16 September 2025
7. Extensions to the HTMLElement Interface
https://www.w3.org/TR/cssom-view/#dom-htmlelement-offsetparent

- - - - - - - - 

(In reply to Jaroslav Zaruba from comment #3)

> Obviously this also means that there is currently no way to compute actual
> offset (position) of an elment with position:fixed.

Correct.

> offsetTop:
> "If the offsetParent of element A is null or the HTML body element return
> the distance, as number of CSS pixels, between the top border edge of
> element A and the canvas origin and stop this algorithm."
> 
> Currently the offsetTop property of position:fixed element always contains 0.

In a test page, I am able to get the offsetTop property of a 'position: fixed' element (which is not 0) with Firefox 47 and Chrome 51. But the spec says it should not be possible since offsetParent of a 'position: fixed' element should be null.