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Re: Using preload for "async" CSS by changing `rel` trick

From: Anne van Kesteren <annevk@annevk.nl>
Date: Sat, 13 Jan 2018 08:43:53 +0100
Message-ID: <CADnb78hxNuQQ_Ev_d6mxgN=nXF7jzDtELssBczpd5oeN9-bJWw@mail.gmail.com>
To: Ilya Grigorik <igrigorik@google.com>
Cc: Ben Maurer <ben.maurer@gmail.com>, Philip Walton <philipwalton@google.com>, Royi Hagigi <royi@fb.com>, "public-web-perf@w3.org" <public-web-perf@w3.org>
On Sat, Jan 13, 2018 at 7:39 AM, Ilya Grigorik <igrigorik@google.com> wrote:
> On Fri, Jan 12, 2018 at 10:24 PM, Ben Maurer <ben.maurer@gmail.com> wrote:
>>>> We use the fact that a resource has been downloaded to reveal content
>>>> that depends on the JS/CSS that we are fetching. So if rel=preload told use
>>>> a.css is available we'll insert HTML that uses a.css into the DOM. Even a
>>>> single frame of the browser doing something like parsing the file would
>>>> create a disruptive user experience.
>>>
>>> Right, I see. I think that's a great use case to raise against HTML spec
>>> and see what the guidance is there — this is not preload specific, same
>>> applies for resources coming from HTTP cache, serviceworker, etc.
>>
>> Is the correct formulation of the question "does the presence of a
>> resource in the fetch group's response cache [which is what the preload spec
>> says it adds the stylesheet to] guarantee that inserting a <link> with an
>> href to that resource will synchronously apply to the DOM"
>
> I'll defer to Anne on this one. :-)

Well, you shouldn't, since this is the complaint I've been making to
you for a number of years now about the state of these features. You
haven't defined them end-to-end, so the answer to these questions
remains unclear. Having said that, I don't think we'd want to give
synchronous guarantees, and especially not that the resource is
already parsed as CSS and has the relevant data structures created.


-- 
https://annevankesteren.nl/
Received on Saturday, 13 January 2018 07:44:19 UTC

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