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List:       webkit-dev
Subject:    Re: [webkit-dev] WebKit position on Paint Timing / (first paint, first contentful paint)
From:       Noam Rosenthal <noam () webkit ! org>
Date:       2020-03-01 22:07:17
Message-ID: CAGttnEWCwLooLEJSPsSW=m1ixdXkDtdYMkifPb_T4BKFJekcPA () mail ! gmail ! com
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[Attachment #2 (multipart/alternative)]


>
>
> The first visually non-empty milestone almost always happens way before
> this point. The above is just a fallback to make sure we eventually hit
> this milestone. For example, if a document is totally blank even after
> loading the document and all subresources, we want to paint it instead of
> waiting forever.
>
> The visually non-empty heuristic is elsewhere.
>
> Note that WebKit would consider the paint triggered by the above fallback
> code to be both a first paint and "first visually non-empty paint" or
> "first meaningful paint", which somewhat corresponds to Chrome's notion of
> "first contentful paint".
>
> First paint can only happen earlier under even more unusual circumstances,
> I believe there is a timeout after which we will paint even if all we can
> paint is blank white or background color.
>
>
> But let's take the specifics to Slack/bugzilla?
>
>
> I think it would be good for you to talk to people who understand WebKit's
> layout/paint milestones in detail before taking things to bugzilla. Ask on
> Slack, and I'll point you to the right people.
>
Oops, just saw this, an initial (not for review) patch is already in
bugzilla :)
But I'll continue the discussion - I have better idea of what to ask now.
Who would be the right people to ask?

[Attachment #5 (text/html)]

<div dir="ltr"><div class="gmail_quote"><blockquote class="gmail_quote" \
style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: \
break-word;"><div><br>The first visually non-empty milestone almost always happens \
way before this point. The above is just a fallback to make sure we eventually hit \
this milestone. For example, if a document is totally blank even after loading the \
document and all subresources, we want to paint it instead of waiting \
forever.</div><div><br></div><div>The visually non-empty heuristic is \
elsewhere.</div><div><br></div><div>Note that WebKit would consider the paint \
triggered by the above fallback code to be both a first paint and "first visually \
non-empty paint" or "first meaningful paint", which somewhat corresponds to Chrome's \
notion of "first contentful paint".</div><div><br></div><div>First paint can only \
happen earlier under even more unusual circumstances, I believe there is a timeout \
after which we will paint even if all we can paint is blank white or background \
color.</div><br><blockquote type="cite"><div><div dir="ltr" \
style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal \
;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><div \
class="gmail_quote"><div><div \
style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stre \
tch:normal;font-size:12px;line-height:normal;font-family:Menlo;color:rgb(155,35,147)"><span><br>But \
let&#39;s take the specifics to \
Slack/bugzilla?</span></div></div></div></div></div></blockquote><div><br></div><div>I \
think it would be good for you to talk to people who understand WebKit's layout/paint \
milestones in detail before taking things to bugzilla. Ask on Slack, and I'll point \
you to the right people.</div></div></blockquote><div>Oops, just saw this, an initial \
(not for review) patch is already in bugzilla :)<br>But I&#39;ll continue the \
discussion - I have better idea of what to ask now.<br>Who would be the right people \
to ask?</div></div></div>



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