749386 - Layout issue with position:relative and margins

Status: NEW

(Core :: Layout, defect)

Description

[Colin Sheaff]

Attachment: HTML reporoducing bug

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:12.0) Gecko/20100101 Firefox/12.0
Build ID: 20120420145725

Steps to reproduce:

A div with position:relative and a left offset of width n with a matching margin-right of width n.


Actual results:

Horizontal scroll bar.


Expected results:

No horizontal scroll bar.

Comment 1

[Jet Villegas (inactive)]

UTR in FF11, regression in FF12.

Comment 2

[Alice0775 White]

Regression window(m-c)
Works:
http://hg.mozilla.org/mozilla-central/rev/0b4c58200e3a
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a1) Gecko/20120117 Firefox/12.0a1 ID:20120117042508
Fails:
http://hg.mozilla.org/mozilla-central/rev/ff1bedd7d463
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a1) Gecko/20120117 Firefox/12.0a1 ID:20120117072408
Pushlog:
http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=0b4c58200e3a&tochange=ff1bedd7d463


Regression window(m-i)
Works:
http://hg.mozilla.org/integration/mozilla-inbound/rev/7ea3311b5e6c
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a1) Gecko/20120116 Firefox/12.0a1 ID:20120116145408
Fails:
http://hg.mozilla.org/integration/mozilla-inbound/rev/3077b729dfd5
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a1) Gecko/20120116 Firefox/12.0a1 ID:20120116153908
Pushlog:
http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=7ea3311b5e6c&tochange=3077b729dfd5

Last good: e176daacecfc
First bad: 7f8cf8e934a5
Triggered by:
7f8cf8e934a5	Benjamin Stover — Bug 665597 - Include margin calculations in FinishAndStoreOverflow. part=1/5 r=roc

Comment 3

[Robert O'Callahan (:roc) (email my personal email if necessary)]

This is expected. We're including the right margin of the position:relative element in the area that you can scroll to.

This is compatible with the CSS spec (which doesn't specify whether to include the margin in the scrollable area or not), and it's reasonably logical. The question is, is it breaking sites?

Comment 4

[Colin Sheaff]

At the very least, this breaks the Pixel-Cookers theme for Redmine (http://pixel-cookers.github.com/RedmineThemePixelCookers/), an example is seen here (https://redmine.sesp.northwestern.edu/).

I'll say that this renders without a horizontal scroll bar in FireFox 11 (OSX/Ubuntu), as well as current builds of Safari(OSX) and Opera(OSX). This may be behavior that's compatible with the CSS spec, but it's not explicitly defined and the de facto standard up until this build was the opposite behavior.