1597100 - Initial layouting of an absolute element inside inline relative element inside absolute element is wrong

Status: NEW

(Core :: Layout: Positioned, defect, P3)

Description

[joonas.mertanen]

Attachment: wrong and correct layouting

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0

Steps to reproduce:

Repro: https://repl.it/repls/SereneLinedScience

Minimal repro was a bit hard to achieve, but having this kind of DOM tree:

• (lowest in hierarchy) <h3 position="absolute" />
• <span position="relative" />
• <div position="absolute" />
  seems to cause a weird initial layouting bug, where the layouting is wrong on the initial render, but corrects itself if you edit some property (eg. toggling "right: 5px" on the h3 off and on fixes the layouting)

Actual results:

The absolutely positioned Date h3 is positioned above the other Title h3

Expected results:

Date h3 should be positioned on same level as Title h3, and actually does get positioned there if you somehow mark the layout as dirty.

Comment 1

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

Attachment: bug1597100-absolute-pos.html

A further reduced test case from comment 0. It looks like the position:absolute's y position is changed only if it is under a position:relative inline.

Comment 2

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

mozregression tried its best to give this range.
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=30ea2905130e85f9e1d8d56fa3097901eec6514b&tochange=67cd1ee26f2661fa5efe3d952485ab3c89af4271

Comment 3

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

Attachment: bug1597100-absolute-pos.html (updated)

Updated test in comment 1.