Re: WG design call - April 12th @ 11am PST

ElementTiming will support images and text. Not sure if you consider that
to cover forms, but I think these two are the building blocks of any

On Wed, Apr 24, 2019 at 9:52 AM Fred Short <> wrote:

> Hi,
>   I initially added this to the video comment section but sending to the
> public-web-perf list as well:
> "Interesting conversation but I think Ryosuke largely has it right. I
> think element size as a proxy for importance to the user won't ultimately
> be useful or relevant since what is important will vary greatly from page
> to page (i.e. what is meaningful for a static web page will be completely
> different to what is meaningful for a business app). Trying to do something
> that "loosely models user experience" will result in something that is
> largely not meaningful to most. The annotation approach via ElementTiming
> is the better approach and will be more useful/accurate in the long run.
> The argument that dev's won't take the time to annotate isn't a good one -
> if they are interested in measuring the user experience of their page, they
> will take the time to do the necessary annotation. A default,
> heuristic-based approach, won't provide much useful information relative to
> their page so they will need to fall back to ElementTiming to get something
> more meaningful for their page. One comment about the ElementTiming spec -
> If I'm reading this correctly, this is initially limited to annotating
> images within the page. This will need to be expanded to include other
> elements (i.e. form elements for starters) before this is going to be truly
> useful for business applications in the wild.”
> Thanks,
> Fred
> On Apr 22, 2019, at 4:45 PM, Yoav Weiss <> wrote:
> (Just realized this email was never sent after the April 12th call.
> Apologies!!)
> Hey all,
> Minutes
> <>
> and video <> from the call are now available.
> Copying them here for safe keeping.
> Cheers,
> Yoav
> WebPerfWG design meeting - April 12th 2019
> Participants:
> Steven Bougon, Gilles Dubuc, Phillippe Le Hegaret, Nicolás Pena, Maxime
> Villancourt, Tim Dresser, Benjamin De Kosnik, Ryosuke Niwa, Andrew
> Comminos, Markus Stange, Nic Jansma, Todd Reifsteck, Yoav Weiss
> Face to Face:
>    - We need to notify everyone 8 weeks in advance.
>    - No date nailed down yet.
>    - Web Games workshop at the end of June
> Next call dates:
>    - Tuesday April 23th @ 9:00am PST
> Largest Contentful Paint: slides
> <>
>  (Nicolás)
>    - Improves on FCP
>    - Looks at the largest text or image.
>    - Stop looking at input or page unload.
>    - Heuristics:
>    - Ignore removed elements.
>    - Ignore background images attached to the body.
>    - Mobile:
>    - Most mobile pages have at least one large image.
>    - Desktop:
>    - May have more page with large text elements.
>    - Ryosuke: why is this important?
>    - Tim: We have had lots of feedback that FCP isn’t sufficient. Element
>    timing is strictly better than LCP, but not everyone will manually annotate
>    for element timing.
>    - Ryosuke: It seems like this is just heuristics. If developers don’t
>    take the time to annotate their websites for ET, why would they care about
>    this?
>    - Yoav: This isn’t just a bunch of heuristics, we’re trying to find
>    the largest element, under the assumption that it is meaningful for the
>    user. There are heusristics related to size of text elements,
>    meaningfulness of BG images, but eventually, we want to use size as a proxy
>    for importance.
>    - Todd: I think the question was “are people asking for this?”
>    - Ryosuke:
>    - Do people want this? Will people use this?
>    - Nicolás: FCP is widely used and we get a lot of complaints that it’s
>    not enough, so no doubt there’s a need
>    - Tim: maybe we need to gather additional data to prove this fills
>    that gap.
>    - Ryosuke:
>    - Safari doesn’t even paint until we think the majority of the web
>    page has painted.
>    - First contentful paint should be equivalent to largest contentful
>    paint.
>    - Nicolás: Is that also true for splash screens?
>    - Ryosuke: won’t that be counted?
>    - Nicolás: That’s why we ignore removed elements
>    - Tim: maybe we should grab some filmstrips from Safari, and eyeball
>    what this metric would do there?
>    - Ryosuke: What Safari aims to do is avoid paint, keep the user
>    looking at the previous screen, until we have enough to paint something
>    meaningful. So this metric will be implementation specific with regards to
>    when things are painted. I can see this being useful in Chrome, but not in
>    Safari.
>    - Todd: At MS, lots of things are built in React, with 3-5 phases of
>    rendering, and only hit “useable” at the 4th phase. IIUC, this API intends
>    to cover some of those scenarios as well.
>    - Tim: yeah. Would going over Safari filmstrips be useful?
>    - Ryosuke: It may be useful, but we’ll consider any difference between
>    this metric and FCP as a bug. Safari wants to wait until the main content
>    has painted.
>    - Gilles: There’s no conclusion if progressive rendering is better
>    than waiting. Otherwise, regarding exceptions around user interaction and
>    scrolling, how much data do we discard?
>    - Nicolás: we don’t discard, we just report the earlier example.
>    - Gilles: How can we avoid bias? You’d be different measurements based
>    on user behavior.
>    - Tim: Hoping that e.g. 90%ile data will be clean, but we can do more
>    research there.
>    - Nicolás: We can discard those cases based on timing.
>    - Gilles: what’s the attribution story?
>    - Nicolás: We expose rects, intrinsic sizes, urls as reported by RT,
>    id when it’s there. Wondering what attribution is required for this to be
>    useful.
>    - Tim: this is different from what Safari does because we can
>    calculate it retroactively, where the browser can’t do that while painting.
>    So I’d expect differences.
>    - Ryosuke: For this to be useful to webdevs, we want a metric that is
>    useful in all browsers. Usecase of wanting to identify when important
>    things have painted makes sense. Suppose you’re writing an editor app,
>    where you first paint a splash screen. The splash screen is a big image.
>    The editor content is empty. What would the metric do?
>    - Yoav: The page will not be a single element which is completely
>    white. Ryosuke - IIUC, this metric and FCP will be very close in Safari?
>    - Ryosuke: I think so.
>    - Yoav: So Safari will still show this metric very close to Chrome’s
>    implemention of it, it’s only FCP that will be significantly delayed, right?
>    - Ryosuke: you can see it that way.
>    - Tim: There’s certainly developer demand for something like this.
>    What would be alternatives we can take?
>    - Benjamin: What about last contentful paint?
>    - Tim: We don’t want to penalize continuous updates and lazy loading.
>    Motivated engineers can create their own metrics using Element Timing.
>    - Yoav: and the goal with this metric is to gather that data for the
>    majority who won’t annotate their elements.
>    - Tim: Ryosuke, any alternatives?
>    - Ryosuke: the idea to measure this has come up multiple times, and we
>    always didn’t find a good algorithm for this. This is just a bunch of
>    heuristics.
>    - Tdresser: Element Timing as a primitives will help us reach a
>    different outcome. FMP was a bag of heuristics. We should solve the problem
>    even if the solution is not perfect.
>    - Ryosuke: heuristics may change in the future.
>    - Nicolás: reasons for heuristics is to exclude some of the images.
>    This is not a black box of heuristics. We want to use the size of the image
>    as a proxy for its relevance.
>    - Ryosuke: the correlation between size and importance is a heuristic
>    in itself
>    - Yoav: I’d be uncomfortable if we said that this is a problem we
>    cannot solve. Developers continuously ask for this.
>    - Gilles: maybe ET usage can help guide us towards the right solution.
>    This is a lot of guesswork. It will probably not work for many other sites.
>    - Steven: we sell a platform for our customers to create their pages,
>    where ET will not work.
>    - Gilles: yeah, but we should give more time for ET to be used. This
>    is making a lot of assumptions regarding the user interaction model. This
>    reminds above-the-fold synthetic metrics. Maybe the future is that people
>    interact more and more early. Input limitation is a problem. So need a
>    metric that captures that interaction as well.
>    - Nicolás: We saw data saying that this is better than FCP
>    - Steven: We sell a platform where customers add components, and want
>    to measure it even if they don’t annotate.
>    - Gilles: we still haven’t given developers a chance to experiment and
>    find patterns that work, which can inform a high-level metric design. This
>    is assuming a lot of the user interaction model and how users behave. This
>    metric becomes less useful as people interact earlier. We need to also
>    capture elements that are below the initial viewport.
>    - Ryosuke: can imagine a webapp where users scroll early to the
>    content they care about
>    - Ryosuke: did you look at pages already using element timing, and
>    seen how well this matches up with LCP?
>    - Tim: very few websites use ET today, but we should look at that.
>    - Yoav: from an analytics provider’s perspective, does this make sense?
>    - Nic: we need something that doesn’t require manual annotation.
>    Generally excited about this, but we’d need to think through the
>    implications of user input stopping the updating of this metric. We’d need
>    to log when interactions occurred as well. But onboard with getting
>    something like this.
>    - Yoav: what I hear from folks is:
>    - Concern from folks around input and abort bias.
>    - Heuristics: how comfortable are folks with a heuristic based
>    approach where the intent is declared, but the heuristic calculation itself
>    is UA defined?
>    - Markus: ideally any heuristics would live in the page, and the page
>    would do the annotation etc. This isn’t feasible though. We’ll need some
>    heuristics in the browser.
>    - Ryosuke: it would be better if the heuristics lived in the analytics
>    provider.
>    - Nicolás: we could relax the constraints and emit more ETs, so that
>    analytics providers can calculate this retroactively.
> <out of time>
> On Fri, Apr 12, 2019 at 3:31 AM Yoav Weiss <> wrote:
>> Hey all,
>> Join us tomorrow for a WG call and talk about new feature designs.
>> On the agenda
>> <>
>> for tomorrow we currently have discussions about Element Timing and Largest
>> Contentful Paint. Feel free to add more items to the agenda if there's
>> something else you'd like to discuss.
>> The hangout for the call would be the usual one
>> <>.
>> See y'all tomorrow,
>> Yoav

Received on Wednesday, 24 April 2019 14:39:13 UTC