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

From: Ilya Grigorik <igrigorik@google.com>
Date: Fri, 12 Jan 2018 22:39:32 -0800
Message-ID: <CADXXVKrNxj7ZZEXspmp2_59NvcGXSWw-brxoTo-U7c9QwwfPiw@mail.gmail.com>
To: Ben Maurer <ben.maurer@gmail.com>
Cc: Philip Walton <philipwalton@google.com>, Royi Hagigi <royi@fb.com>, "public-web-perf@w3.org" <public-web-perf@w3.org>, Anne van Kesteren <annevk@annevk.nl>

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. :-)
Received on Saturday, 13 January 2018 06:40:36 UTC

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