625703 - A flexbox (display:box) element’s margins aren’t collapsed with surrounding elements

Status: NEW

(Core :: General, defect)

Description

[Oli Studholme]

User-Agent:       Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b8) Gecko/20100101 Firefox/4.0b8
Build Identifier: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b8) Gecko/20100101 Firefox/4.0b8

Refer to an example at http://oli.jp/bugs/mozilla/flexbox-margin-collapsing.html

Reproducible: Always

Actual Results:  
the margins of an element using display: box to trigger flexible box layout don’t collapse with the margins of surrounding elements

Expected Results:  
margins should collapse as usual

Comment 1

[Boris Zbarsky [:bzbarsky]]

Yeah, the margin-collapsing code all lives in nsBlockFrame.  This is basically the same as bug 87277.

Comment 2

[u279076]

Based on comment 1, should this be duped?

Comment 3

[Daniel.S]

Attachment: three box siblings

(In reply to comment #1)
> Yeah, the margin-collapsing code all lives in nsBlockFrame.  This is
> basically the same as bug 87277.

I don't think it is the same issue.

If you look at my testcase, you can see that we treat -moz-box like an inline-block, while WebKit and IE treat it like a block box.

Also, unlike bug 87277 this issue won't be fixed by bug 659828.

I can't tell who's right.

Comment 4

[Jose Fandos]

Confirming

Comment 5

[Oli Studholme]

Just FYI this is regarding OLD Flexbox (display: box;), not NEW Flexbox (display: flex;), and the chances of it being fixed are probably not great. For more background:
https://bugzilla.mozilla.org/show_bug.cgi?id=625694

Comment 6

[Daniel.S]

If I read bug 625694 correctly, this bug is either Invalid (since whatever -moz-box does is intended) or Won'tFix (since whatever -moz-box does is being relied on), is it not?

I'd like to add some margin-collapsing tests for -moz-box (in bug 477462), and if there is no bug, I won't mark those test failing.

Is -moz-box going to go away anytime soon, as hinted in bug 625694?

Comment 7

[Boris Zbarsky [:bzbarsky]]

> Is -moz-box going to go away anytime soon

In general no, but for websites, hopefully yes...

Comment 8

[chharvey]

Also please remember to update the “[Mastering margin collapsing](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Box_Model/Mastering_margin_collapsing)” article.

In this article, there is no mention of whether the vertical margins of an element with `display: flex;` should/should not collapse with the vertical margins of its first and last child (as of 2016-07-12 they still do not collapse). This information should be explicitly added to the article to reduce confusion.