Intent to implement and ship: CSS display:flow-root

[Mats Palmgren]

Summary:
A display:flow-root element generates a block container box, and lays out
its contents using flow layout. It always establishes a new block
formatting context for its contents (per CSS2).
This is intended to make "clearfix" hacks unnecessary.

The implementation is fairly trivial: it adds a new keyword to
the 'display' property and ties that to existing code for
"NS_NewBlockFormattingContext".

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1322191

Link to standard:
https://drafts.csswg.org/css-display-3/#valdef-display-flow-root

Platform coverage: all platforms

Estimated or target release: Fx53

Preference behind which this will be implemented:
layout.css.display-flow-root.enabled

DevTools bug: no need

Do other browser engines implement this?
Not that I am aware of, bugs have been filed for WebKit/Blink:
https://bugs.webkit.org/show_bug.cgi?id=165603
https://bugs.chromium.org/p/chromium/issues/detail?id=672508

Tests: added as part of the implementation

Security & Privacy Concerns: none


/Mats

[L. David Baron]

Sounds good to me, except that I think it's worth explicitly raising
on www-style that we're planning to ship this, since the spec for it
isn't yet in (or near) CR. (The bug says the editors believe the
feature is stable enough to ship, but that's worth raising more
widely before we ship it.)

-David

--
𝄞 L. David Baron http://dbaron.org/ 𝄂
𝄢 Mozilla https://www.mozilla.org/ 𝄂
Before I built a wall I'd ask to know
What I was walling in or walling out,
And to whom I was like to give offense.
- Robert Frost, Mending Wall (1914)

[mtan...@yandex.ru]

Fwiw, there is also a feature request for Edge:

https://wpdev.uservoice.com/forums/257854/suggestions/17420707

originally posted as a bug (but closed on the ground that the bug tracker is for bugs while feature requests should go to UserVoice):

https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/10152756/

For some reason cannot add any of those two URLs to the “See Also” field in Bugzilla: it rejects with the message “Invalid Bug URL” (looks like there is some white list of bug trackers that doesn’t account for Microsoft’s bug trackers).

[Daniel Holbert]

On 12/21/2016 10:57 AM, mtan...@yandex.ru wrote:
> Fwiw, there is also a feature request for Edge:
>
> https://wpdev.uservoice.com/forums/257854/suggestions/17420707

[...]

> https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/10152756/
>
> For some reason cannot add any of those two URLs to the “See Also” field in Bugzilla: it rejects with the message “Invalid Bug URL”

This linking issue is tracked in
https://bugzilla.mozilla.org/show_bug.cgi?id=1322371 (at least for
developer.microsoft.com, and I added a note there about the uservoice
URLs as well).

~Daniel

[Mats Palmgren]

FYI, Chrome is following our lead and now intend to ship too:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/k9WOAVA5Ewc

/Mats