On Feb 16, 2013, at 10:50 PM, Maciej Stachowiak <m...@apple.com> wrote:

> 
> On Feb 16, 2013, at 10:16 PM, Dirk Schulze <dschu...@adobe.com> wrote:
> 
>> 
>> On Feb 16, 2013, at 6:54 PM, Adam Barth <aba...@webkit.org> wrote:
>> 
>>> It's much easier to discuss a concrete example.  Which interface are
>>> you interested in deprecating?
>> 
>> I can understand that it is easier to discuss on a concrete example, even if 
>> I would like to discuss this in a general scope. We have multiple interfaces 
>> that we may want to deprecate at some point.
>> 
>> A concrete example I thought about is WebKitCSSMatrix[1]. It is not used in 
>> WebCore yet but hopefully replaced by a standardized Matrix interface in the 
>> future[2]. This new interface will not be fully compatible to 
>> WebKitCSSMatrix and I would like to warn authors before they actually start 
>> using it.
> 
> Since you're the one designing the new interface (or at least you are the 
> spec editor), why don't you just make it compatible? Breaking changes to 
> existing Web APIs should only be done as a last resort, and I don't 
> understand the justification for doing it here.

It is a proposal so far and no draft yet. Technically, I am not the editor of 
it so. The proposal has quite some way to go (hopefully not too much) and I do 
not plan to land anything in this direction as long as the responsible WGs did 
not agree on continuing with the proposal and the general direction. I will 
post a separate mail with the actual feature implementation announcement when 
the time comes.

> Then we have a much simper transition story, and WebKitCSSMatrix can be 
> aliased to the new class.

I indeed tried to preserve the behavior of WebKitCSSMatrix as much as possible. 
I got an action of the SVG WG to work on a replacement for SVGMatrix. The 
highest priority was to preserver the behavior of SVGMatrix (which is 
definitely actively used by web content) and provide a basic interface that can 
be used beyond just SVG. There are a lot of use cases in the near future for a 
generalized matrix IMO. SVG, CSS Transforms, Canvas and WebGL are the obvious 
once. A specification interoperable format to share transformation data seems 
extremely desirable. I encourage everyone who is interested to look at the 
proposal and give feedback.

> 
>> 
>> Again, I think it would be better to discuss this in a wider scope but am 
>> happy to discuss it on the concrete example as well. This actually might 
>> make it easier to come up with general rules in the future.
> 
> I think spamming the console is not a useful thing to do for interfaces that 
> actually have significant usage in the wild. A more productive step would be 
> to measure usage of WebKitCSSMatrix. If it's reasonably high, we're not going 
> to be able to remove it.

I agree that we need more metrics to discuss the next active steps on 
WebKitCSSMatrix and I already uploaded a patch to add it to the 
FeatureObserver[1].

The question remains: How do we want to continue with deprecating WebKit 
specific features in the long term. Especially when we have a standard 
compliant replacement. It is extremely hard to maintain all different 
behaviors. So far we have multiple implementations of background, flex-box, 
gradients to name some. This doesn't scale very well and there will be a time 
where we can not guarantee for the correct functioning of old features. This is 
a problem that other browsers like IE are focused for quite some time as well 
(not necessarily successfully). As long as we are concerned to deprecate and 
remove features, we increase the complexity of the code base. Less and less 
reviewers will be able to determine the behavior of patches to the general code 
base, while we increase the feature count and interoperability between modules 
more and more. There is no other way then to risk breaking content that relies 
on non-standardized behavior of platforms. And we should formalize this t
 o give a bit more reliability to web authors. The last section on [2] is too 
vague at the moment.

Greetings,
Dirk

[1] https://bugs.webkit.org/show_bug.cgi?id=110002
[2] http://trac.webkit.org/wiki/DeprecatingFeatures


> 
> Regards,
> Maciej
> 
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