1096003 - CSS not always processed the same way

Status: NEW

(Core :: CSS Parsing and Computation, defect)

Description

[Jesper Hansen]

The CSS processor doesn't always see the rule font-size : 13; on line 83 in http://www.heroes.dk/inc/forum.css
This results in the forum section headlines to occasionally be shown with bigger text

The bug can't be triggered with refresh. It can however be triggered by going to the urlbar and pressing enter.

(screenshots will follow)

Comment 1

[Jesper Hansen]

Attachment: font-size: 13; is seen

Comment 2

[Jesper Hansen]

Attachment: font-size: 13; is ignored

Comment 3

[Cameron McCormack (:heycam)]

Thanks for the bug report, Jesper.  I can't reproduce the issue myself with Firefox 33 on Windows 8.1.  What version are you using?  How many times do you need to refresh the page before you see the bug?

The correct behaviour is for the |font-size: 13| rule to be dropped, since it needs a px unit on the end.  If sometimes it is getting treated as 13px automatically, this is a bug.

Comment 4

[Jesper Hansen]

I'm on Nightly, 36.0a1 (2014-11-07). Addons: Image in New Tab, Modify Headers, PasswordMaker and Session Manager.

The Nightly hasn't been restarted since reporting this and it does appear to be behaving better.
Not perfect, but better. I can't get it to bug with F5 refreshing, but visiting the page again--- I take that back, I could just now get it to happen after using Ctrl+r.
Is there some part of the CSS processor that reacts to the font-size and tries to "fix" it, but doesn't cache that result.

Comment 5

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

Unitless lengths are allowed in a number of contexts in quirks mode, for certain properties.  See https://quirks.spec.whatwg.org/#the-unitless-length-quirk

Comment 6

[Boris Zbarsky [:bzbarsky]]

This page is in standards mode...

Jesper, can you tell me what document.compatMode is for you when you see the two different renderings?

Comment 7

[Jesper Hansen]

Attachment: CSS1Compat with red guidelines

I see that it is showing as CSS1Compat in both cases.
I added guide lines so I could actually tell the difference. Tho more noticeable on the when tabbing between the first two screenshots