On 03/18/2014 11:26 AM, Cameron McCormack wrote:
CSS Variables is a feature that allows authors to define custom properties that
cascade and inherit in the same way that regular properties do, and to
reference the values of these custom properties in the values of regular
properties (and other custom properties too).
http://dev.w3.org/csswg/css-variables/
I blogged about the feature when it initially landed here:
http://mcc.id.au/blog/2013/12/variables
It lives behind the layout.css.variables.enabled pref, which is currently
enabled by default only on Aurora/Nightly.
One thing from the specification that we don't implement is the CSSVariableMap,
but Tab tells me that this is going to be removed from the spec.
I intend to enable this feature by default this Friday (March 21). That would
target Firefox 31.
The spec has been stable for a while, and the CSS Working Group already has a
resolution to publish the document as a Candidate Recommendation.
There has been a last minute proposal for a change to the syntax of custom
property declarations, to align with other custom features in CSS that are
coming down the pipeline (such as custom media queries). There are a couple of proposals
on the table: to replace the "var-" prefix of the name of
the custom property with a "_" prefix, or perhaps just anywhere within the name. Similarly for
"--" rather than "_".
Tab wants to discuss this in this week's CSS Working Group telcon, so if the
decision is made quickly enough we can update our implementation. The CSS
Working Group is aware of our plans to ship.
Bug to enable this feature: https://bugzilla.mozilla.org/show_bug.cgi?id=957833
Blink until recently had an implementation of CSS Variables, behind a flag, but
not one that supported the fallback syntax (or CSSVariableMap). They
have recently removed it saying that they need to rewrite as it had poor
performance, but they say they are still interested in the feature
Curious, how much have we tested the performance of our implementation and are
there some known perf issues?
-Olli
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