Re: [NavigationTiming2] Comments and questions about the Navigation Timing 2 draft

On Thu, Oct 11, 2012 at 10:26 AM, Boris Zbarsky <bzbarsky@mit.edu> wrote:

> *TL;DR:* In my opinion, time to first paint is definitely more than a
>> "feel good" metric. In fact, it is something we want to highlight to
>> site owners and developers and get them thinking about.
>>
>
> OK.  I agree that we want people to think about the issue of layout and
> painting being blocked on scripts.
>
> The hard bit for me is that the common user-perceived lag has to do with
> one of two things, as far as I can tell:
>
> 1)  Layout not starting due to pending scripts/stylesheets.  This has
> nothing to do with painting per se.
>
> 2)  Layout starting but there not being anything to render because it's
> all generated via script onload or on DOMContentLoaded or is display:none
> until something happens.  This would not be detected by a "first paint"
> metric, because the browser will happily paint a white viewport.


Right, both (1) and (2) are contextual to each individual page. However,
perhaps somewhat naively, I still equate the "layout flush" to "first
paint".. That is, coming back to "user sees something" definition. What the
user sees is a separate story for the site owner to worry about. For Gmail,
it's a loading screen, for another site it may be a blank frame - we should
leave this to the site owners.

Ilya