Re: [Shadow DOM] Simplifying level 1 of Shadow DOM

On Wed, May 1, 2013 at 12:15 PM, Dimitri Glazkov <> wrote:
> On Wed, May 1, 2013 at 11:49 AM, Ryosuke Niwa <> wrote:
>> On Apr 30, 2013, at 12:07 PM, Daniel Freedman <> wrote:
>>> I'm concerned that if the spec shipped as you described, that it would not be useful enough to developers to bother using it at all.
>> I'm concerned that we can never ship this feature due to the performance penalties it imposes.
> Can you tell me more about this concern? I am pretty sure the current
> implementation in WebKit/Blink does not regress performance for the
> Web-at-large.

Note that the interesting restriction isn't that it "shouldn't regress
performance for the web-at-large". The restriction is that it
"shouldn't be slow when there is heavy usage of Shadow DOM on the

Otherwise we recreate one of the problems of Mutation Events. Gecko
was able to make them not regress performance as long as they weren't
used. But that meant that we had to go around telling everyone to not
use them. And creating features and then telling people not to use
them is a pretty boring exercise.

Or, to put it another way: Don't create footguns.

/ Jonas

Received on Wednesday, 1 May 2013 19:42:07 UTC