1303317 - Incorrect position:fixed within flex model

Status: VERIFIED DUPLICATE of bug 874718

(Core :: Layout, defect)

Description

[master.skywalker.88]

Attachment: flex_fixed.html

User Agent: Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36

Steps to reproduce:

I created a container with several elements aligned using display:flex. One of them has position:fixed.


Actual results:

The element with position: fixed correctly resists to scroll, but its position is determined as if its container had no flexible display. Non-fixed elements are correctly positioned.


Expected results:

position:fixed should not interfere with flex. In Edge, Opera and Chrome the element takes its position in the flex model, but it remains still while scrolling.

Comment 1

[Mats Palmgren (inactive)]

Dupe of bug 874718?

Comment 2

[Daniel Holbert [:dholbert]]

Yeah, this is bug 874718.

(Mr. Skywalker, just to provide some background here -- Firefox's behavior is correct according to an *old* verison of the spec -- and the spec went through several additional intermediate plans for how this should behave, before settling on the final behavior that you're expecting.  Thanks for the bug report, and it should hopefully be fixed in Nightly soon!)

(I've been working on this and have some patches which are very nearly review-ready, but over the past few weeks I've been focusing more on catching up on (i.e. not-falling-too-far-behind on) code-reviews, as well as helping some interns finish up their summer projects.  I expect to have patches up on helper bug 1269046 early next week, though -- and then this should be fixed soon thereafter.)

Comment 3

[master.skywalker.88]

When I approached at this issue (using position:fixed together with flex) I supposed there were no spec solution for this use case and therefore UAs could behave inconsistently (I was going to write to the public CSSWG mailing list).

I also figured out that most, if not all, could display the coupled properties as FF currently does (IE last version does, while Edge doesn't - another evidence for spec fix, in case I needed it). It came as a surprise that the other UAs did it differently. That's the only reason why I filed it here rather than elsewhere :)

Thanks for all your effort, as well as for the insight you offered me!

Cheers,
Andrea "AndySky21" Rendine

Comment 4

[Daniel Holbert [:dholbert]]

Verified locally that this was broken in Nightly 2016-10-31 & working in Nightly 2016-11-01, which means this is VERIFIED dupe of bug 874718.

(The functionality associated with bug 874718 first shipped in the 2016-11-01 nightly.)