[Webkit-unassigned] [Bug 103208] Don't use ComposedShadowTreeWalker in NodeRenderingContext when SHADOW_DOM is not enabled

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=103208





--- Comment #10 from Dimitri Glazkov (Google) <dglazkov at chromium.org>  2012-11-26 21:50:54 PST ---
(In reply to comment #7)
> Web Components code should be fully behind a feature flag like all other experimental features. Platforms that are not interested in this feature shouldn't need to take the performance and binary size hit from it. Also it is not ok to make other parts of WebKit internals depend on experimental features. The original implementation of <details> did not have such dependency.
> 
> The feature define should be renamed to WEB_COMPONENTS or similar. SHADOW_DOM is a bad name as we have tons of internal shadow DOMs that don't depend on most of this code.

As I mentioned at this year's WebKit contributors meeting (http://webkitmemes.tumblr.com/image/21402870608), all of our internal shadow DOMs use the same plumbing. It's all been painfully specified here (http://www.w3.org/TR/shadow-dom/). SHADOW_DOM intentionally guards only the public-facing API, because most of it had been just a reshaping of the existing custom shadow DOM code we keep writing for every darn HTML element. Most of the Shadow DOM spec is just writing down lessons I learned from that refactoring.

Speaking of which, the initial, hard-coded implementation of <details> was so bad that you would've cried tears of blood just looking at it. There are lots of tiny details that we figured out and made sure they worked right with insertion points, from accessibility to hit-testing, to event retargeting and rendering. I somehow doubt that there's a noticeable binary size hit. I'd bet that a proper <details> implementation in itself would've been a hefty chunk of code.

I understand your frustration and I totally agree that we should fix the performance regression though. We suck and we should fix it -- and we will. And may Kling create a thousand ghastly memes featuring me and Morrita if we don't.

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