Re: Ready indicator

This is something that keeps coming up in various contexts. I agree
that it really needs to be addressed.

Browsers commonly take "screenshots" of websites and display those on
the "new tab" page or elsewhere where they want to display a thumbnail
of a website. Those often end up creating a snapshot at more or less
random points during the loading sequence.

Likewise, if we're ever going to enable a better navigation experience
where the UI can smoothly transition from the current page to the next
page, we'll need to know when the next page is ready to be rendered.

So I definitely agree that we need a standardized way for a page to
indicate "I'm now rendered" so that the UA can build various features
on top of that.

Possibly we'll end up wanting something slightly more complex, like
"I'm rendered enough that it makes sense to display the page" vs. "I'm
done rendering". The former could be when the "UI" of a page has been
rendered, whereas the latter has also loaded and rendered dynamic
data. The two might be very different in a world where the UI has been
cached in a service worker, but the latter requires hitting the
network. But I think even a simple "I'm rendered" would go a long way.

/ Jonas



On Fri, Oct 10, 2014 at 10:08 AM, Eli Perelman <eperelman@mozilla.com> wrote:
> Hello,
>
> In my experiences working on tooling for performance on Firefox OS, I have
> run into a difficult situation in timing the launch time of various
> applications. These applications are built using Web-standard technologies,
> e.g. JavaScript, CSS, and HTML (as such I may use app and site
> interchangably). In order to effectively measure the amount of time an
> application took to launch, I would need to know at which moment the
> application is loaded. Using standard web technologies in the past, we would
> often rely on indicators of window load or the last tick of the event loop
> to determine that everything has been completed, but unfortunately in
> today's world of dynamic loading, this just isn't deterministic.
>
> There is no reliable way to infer the loading time of an application, or any
> website for that matter. Each instance has the power to defer loading of
> all, some, or none of their assets. The window load event does not represent
> a state in every site or app that deems it usable from a user standpoint. By
> using an arbitrarily-inferred event for assessing launch performance,
> engineers are encouraged to defer as much loading as possible in an effort
> to thwart timing metrics.
>
> I believe that if we cannot infer this "ready" state of a site, then the
> site must have the power to imply it. By introducing a performance API where
> a site can infer what it determines to be its "ready" state, we can provide
> better value to tooling by making metrics more directly correlated with
> user-perceived launching. It also has greater use cases outside of just
> performance tooling, as it can be used as an indicator to engines to
> possibly optimize the loading of content or even updating its UI in a more
> intelligent fashion. It would also encourage developers to load assets in
> the manner that makes sense for them in the development process, and not
> destroying their workflow for the sake of "boosting the numbers".
>
> For Gecko, we believe this would be interesting to implement, and can
> propose a possible API if this group finds interest in exploring the idea.
> We would also be interested to discover if there is any prior art in this
> domain.
>
>
> Thanks,
>
> Eli Perelman
> Software Engineer, Firefox OS

Received on Saturday, 11 October 2014 08:07:43 UTC