[webkit-dev] Adding ENABLE_FLEXBOX to WebCore

Tony Chang tony at chromium.org
Thu Jun 9 15:00:25 PDT 2011

On Thu, Jun 9, 2011 at 1:19 PM, Sam Weinig <weinig at apple.com> wrote:

> Why should we implement this spec? We already have one flex box
> implementation that we can never remove (and corresponds closely to
> Firefox's) so it seems to me that we should work on standardizing that
> model. Adding a large bunch of code that duplicates existing functionality
> seems foolish.

There was an attempt to standardize the old flexbox (
http://www.w3.org/TR/2009/WD-css3-flexbox-20090723/), but that effort seems
to have fizzled.  I attempted to write some patches to make WebKit's old
flexbox implementation match that spec, but Hyatt recommended against that
because it can only break sites that are targetting WebKit's existing
flexbox implementation.  WebKit's implementation and Firefox's
implementation are different enough that the current uses of flexbox are
mostly browser specific (e.g., dashboard widgets).

If the issue is the syntax for describing flexing, perhaps the spec should
> be written in a backwards compatible way, that supports both the new syntax
> and the old syntax, but the underlying implementation can remain.

The new syntax describes a superset of features provided by the old syntax.
 I think it's possible to implement the old flexbox on top of the new
flexbox implementation and that seems like a worthwhile goal, but it'll
probably easier to see the similarities for refactoring after the code has
been written.

> On Jun 8, 2011, at 10:57 AM, Tony Chang wrote:
> Hi webkit-dev,
> I wanted to let you know that Ojan and I plan to add flexbox layout support
> to WebCore.  WebCore already supports an older flexbox implementation
> (display: box), but the new spec is designed to be easier for developers to
> understand and more powerful.  The old flexbox will still remain in WebCore
> since none of the CSS properties overlap with the new flexbox spec.  The
> spec can be found at: http://www.w3.org/TR/css3-flexbox/ (
> http://dev.w3.org/csswg/css3-flexbox/<http://dev.w3.org/csswg/css3-flexbox/#negative-flexibility>
> )
> This support will be behind the ENABLE_FLEXBOX feature define (
> https://bugs.webkit.org/show_bug.cgi?id=62049) and there is a meta bug
> tracking the feature's development (
> https://bugs.webkit.org/show_bug.cgi?id=62048).  I expect this feature to
> eventually be enabled by all ports.
> I am ready to setup a buildbot for tracking the compile and flexbox related
> layout tests.  Should I go ahead and get this added to build.webkit.org's
> waterfall?
> Thanks,
> Tony
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