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

On Wed, Oct 10, 2012 at 7:44 PM, Boris Zbarsky <bzbarsky@mit.edu> wrote:

> On 10/10/12 10:33 PM, Ilya Grigorik wrote:
>
>> Boris, could you elaborate on this?
>>
>
> Sure.  How are you defining "first paint"?
>
> Is it when the page bits start being converted to a display list?  When
> the display list starts being rasterized to buffers?  When rasterization
> finishes?  When compositing of the buffers starts?  When it finishes? What
> happens when compositing starts before rasterization finishes? What happens
> if compositing is happening completely in parallel with everything else
> that's going on, on a separate thread or in a separate process?  Do you
> still care when it starts or stops?  Same question about rasterization.
>
> Or more to the point, what information are people actually looking for
> from this "first paint" value?
>
> And note that if what they're looking for is "user sees something" then
> none of the above are correct and the correct number is when something
> appears on the monitor, which can be many milliseconds (sometimes hundreds
> of milliseconds) after all the things I mention above.


Interesting, thanks! I think the intuitive definition for 99.9% of people
who do not live inside the graphics stack is the last one that you
suggested, which is the "user sees something, anything...". Granted, I
think you're hinting at the fact that even that is not 100% accurate due to
hardware and other factors that are outside of our control, but I hope we
can find and agree on a reasonable definition.

Do you have any suggestions for best way to measure this?

Ilya