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Re: NavigationTiming event for initial display

From: Shubhie Panicker <panicker@google.com>
Date: Thu, 23 Jun 2016 08:21:09 -0700
Message-ID: <CAK7ODi_YgRcmKxBD=cLUd1eYhTv66jRaOUgt0_bPRAxbToMZbA@mail.gmail.com>
To: Bryan McQuade <bmcquade@google.com>
Cc: Stefan Seifert <nine@detonation.org>, public-web-perf <public-web-perf@w3.org>, Paul Irish <paulirish@google.com>
We just discussed this at this Wednesday's W3C F2F meeting (great timing :))
The general consensus was on moving forward with *FirstPaint* and
*FirstContentfulPaint*  (something more than blank screen, such as the top
app bar) to start with. Captured in Ilya's meeting notes
<https://www.w3.org/2016/06/WebPerfWGroadmap.html> at the bottom under
"Milestone 3: Nav Timing"

We also discussed "FirstMeaningPaint" (Paul can share pointer), as a future

On Thu, Jun 23, 2016 at 8:12 AM, Bryan McQuade <bmcquade@google.com> wrote:

> Thanks for starting this discussion. This has been an area of interest
> recently, and I believe there's a desire to expose display-oriented metrics
> to the web platform. +Paul Irish <paulirish@google.com> has been working
> on some possible display-oriented metrics and may be able to share more
> about this.
> We do currently expose a first paint timing
> via chrome.loadTimes().firstPaintTime, however chrome.loadTimes() is an
> old, non-standard API and we're hoping to standardize some paint/display
> timing information and then deprecate chrome.loadTimes().
> IIUC IE also exposes a similar performance.timing.msFirstPaint.
> So there's no standard APIs available today, but I agree there should be.
> Paul can share more about the thinking with progressive web metrics.
> On Thu, Jun 23, 2016 at 9:13 AM Stefan Seifert <nine@detonation.org>
> wrote:
>> Hi!
>> Trying to bring facts into a discussion about the merits and harm of using
>> Javascript to lazily load images, I've been looking through the
>> documentation
>> about timing interfaces. While Navigation Timing seems to offer a wealth
>> of
>> information, the one point that would be most helpful for me is the time
>> to
>> initial display, i.e. when the browser first displays rendered content.
>> This is the time, people try to optimize by using lazy image loaders which
>> then rob the browser any chance to make a better informed decision based
>> on
>> all the information it has. The first step in optimization is of course
>> creating a reliable and meaningful benchmark. In absence of timing
>> information
>> offered by the browser (which should be the entity that knows best),
>> people
>> have to resort to opaque web services claiming to use elaborate camera
>> setups
>> or even worse - tribal knowledge spread at conferences and in blog posts.
>> Would it be feasible to add such an event to Navigation Timing or is this
>> information already available in some form?
>> Thanks and regards,
>> Stefan Seifert
Received on Thursday, 23 June 2016 15:21:43 UTC

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