On 12/10/11 3:26 AM, Tab Atkins Jr. wrote:
On Mon, Oct 10, 2011 at 7:51 PM, Sean Hogan<shogu...@westnet.com.au>  wrote:
On 24/09/11 7:16 AM, Adam Klein wrote:
- Is free of the faults of the existing Mutation Events mechanism
(enumerated in detail here:
A simpler solution that is free from the faults listed in that email would
be to have (at max) one mutation observer for the whole page context. I
guess this would be called at the end of the task or immediately before page

If a js lib (or multiple libs) want to provide finer grained mutation
handling then let them work out the details.
That seems unworkably restrictive.  It's very easy to imagine multiple
libraries listening for different kinds of things at the same time.
Libraries would just end up re-implementing event distribution, which
is something we can avoid by doing it correctly now.

This proposal doesn't entirely avoid the issue of event distribution. There is no equivalent of event.stopPropagation() and hence no way to prevent mutation records being delivered to observers. The observers may have to be written with this is in mind.

For example, what if two observers can potentially handle the same mutation - which one should handle it?

Alternatively, some code might respond to an attribute by adding content to the DOM. What if there are mutation listeners that could respond to that added content? Is it desired that they ignore or handle it?

Another pattern that doesn't seem to be reliably handled is mutations within DOM fragments that are temporarily removed from the document. That is: - if the fragment always remains in the document then all mutations can be monitored by observers on the document (or document.body), but - if the fragment is removed from the document followed by mutation observers being called, then any further mutations won't be delivered to the observers, even when the fragment is reinserted into the document.

The exact behavior in this scenario depends on whether mutations complete within one microtask or more than one


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