Are you proposing new mutation record type? I think that could handle most of the enter/leave requirements.
observer.observe(target, { element: 'x-foo' }); If MutationObservers are an open topic for extension, I'd love to see generic css selector support. observer.observe(target, { selector: 'foo' }); observer.observe(target, { selector: '.foo' }); That'd cover element name "enter" and "leaves" as well. On Tue, Feb 11, 2014 at 7:41 PM, Ryosuke Niwa <rn...@apple.com> wrote: > Hi, > > I’m bringing this up out of: > > [Custom]: enteredView and leftView callbacks are still confusing > https://www.w3.org/Bugs/Public/show_bug.cgi?id=24314 > > Could someone clarify exactly why mutation observers can’t satisfy use cases > for custom elements? > > I strongly believe that we should extend mutation observers (e.g. add some > flag to fire more eagerly) so that we could *explain* these callbacks in > terms of mutation observers. > > - R. Niwa > >