[webkit-dev] Unprefixing DOM MutationObservers, and looking for help from port maintainers

Adam Klein adamk at chromium.org
Fri Jun 15 10:31:09 PDT 2012

An update: it appears that the GTK and EFL ports have added at least
basic support for end-of-task delivery, in
http://trac.webkit.org/changeset/108628 and
http://trac.webkit.org/changeset/110568. They now pass all
MutationObserver tests. Do these tests pass in the actual browsers
built from GTK and EFL, or only DRT?

On Fri, Jun 8, 2012 at 2:16 PM, Adam Klein <adamk at chromium.org> wrote:
> Hi webkit-dev,
> DOM MutationObservers (see meta bug
> https://bugs.webkit.org/show_bug.cgi?id=68729) have been shipping as
> WebKitMutationObserver in Chromium since earlier this year. The
> feature is fully specced as part of DOM4
> (http://www.w3.org/TR/domcore/#mutation-observers) and is implemented
> in Firefox. Mozilla has also recently unprefixed their version of the
> API (https://bugzilla.mozilla.org/show_bug.cgi?id=749920), and I'd
> like to do the same (https://bugs.webkit.org/show_bug.cgi?id=85161).
> The tricky part is that while the Chromium version is complete and
> compatible with Firefox, there's one piece missing from all other
> ports (https://bugs.webkit.org/show_bug.cgi?id=78290). The short
> version is that each port needs to be able to run some code
> (delivering mutations) at the end of every task (see
> http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#processing-model-2,
> step 4 "Perform a microtask checkpoint"). Without this code, mutations
> due to user input are not delivered in a timely fashion.
> It's easy for Chromium to do this because we have our own MessageLoop
> abstraction wrapping the native event loops on various platforms, so
> our definition of end-of-task is easy to define. But implementing this
> properly is likely to be slightly different for every port.
> In the short term, my plan is to add the unprefixed version (in
> addition to the prefixed) of MutationObserver when PLATFORM(CHROMIUM)
> is enabled. But I'd like to help other ports implement this
> appropriately, and provide the unprefixed version there too. Please
> let me know how I can be of assistance.
> Let me know if you have questions or concerns,
> Adam Klein

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