[webkit-dev] DOM Mutation Events. WAS: Fwd: webkit editing rewrite?

Maciej Stachowiak mjs at apple.com
Wed Aug 11 07:06:38 PDT 2010

On Aug 9, 2010, at 8:21 PM, Timothy Hatcher wrote:

> On Aug 9, 2010, at 7:52 PM, Dimitri Glazkov wrote:
>> I am very, very tempted to just get rid of them. As Ojan indicated,
>> the use cases for DOM Mutation events are extremely limited and to me,
>> most of them feel like we should be solving them differently anyway.
>> However, with the introduction of extensions into Chromium and Safari,
>> DOM Mutation events experience a sort of renaissance, being used to
>> sense the DOM changes to re-apply modifications (rewrite URLs, text,
>> etc.).
>> So I think we will upset a bunch of extensions developers if we just
>> go cold turkey, which is probably not the right thing -- regardless of
>> whether techniques they employ are sound or not.
>> With this in mind, I think we should do #1 and #3, then #2 after some
>> time and loud over-communication (like Inspector warnings, blog posts,
>> billboards on Hwy 101 etc.).
> Adding input/beforeinput events (#3) wont solve the need of most extension developers that use mutation events today (the examples you cite). So that makes it hard to remove them, especially over time, no matter how much warning you give.

Would it satisfy extension use cases if DOM mutation events got batched and dispatched asynchronously as the generic DOMSubtreeModified?[1] Do extensions need detailed change notification, or is a general "something changed" notification good enough?

I think reducing mutation event support down to just DOMSubtreeModified, and firing it only at the very end of operations that should be atomic, would greatly reduce the risk of mutation-event-induced crashing, but would probably still serve the key use cases.

For performance reasons, it would be even better to have a type of notification that doesn't have to allocate an event object, as that is a large part of the performance hit from mutation events. I gather that is what the fancier new mutation events proposal does.


[1] http://www.w3.org/TR/DOM-Level-3-Events/#event-type-DOMSubtreeModified

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