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Re: Comments about lazyload & postpone

From: Yoav Weiss <yoav@yoav.ws>
Date: Thu, 26 Sep 2013 07:12:17 +0200
Message-ID: <CACj=BEidqpmwA4OTdVvEpp2PJHsx786J19y3WALBHx_CRJ-pGw@mail.gmail.com>
To: "Podjarny, Guy" <gpodjarn@akamai.com>
Cc: "public-web-perf@w3.org" <public-web-perf@w3.org>
Great questions. (and no answers so far?)

One more question:
* Will lazyload/postpone enable link element with a non-matching media
attribute to avoid being loaded altogether?

Regarding link elements, I think we can use 'postpone' on them to indicate
to the browser "load this resource ASAP, but only if it has a matching
media attribute. Otherwise, don't load it at all".

That would answer the use case of page critical stylesheets, that are only
critical for some form factors, but not others.



On Fri, Sep 6, 2013 at 4:04 PM, Podjarny, Guy <gpodjarn@akamai.com> wrote:

> All,
>
> I recently read through the "Resource Priorities" draft (
> https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/ResourcePriorities/Overview.html
> ).
> I really like it, and feel like it captures the vast majority of what I'd
> like to see in such a capability.
>
> I do have a few comments/thoughts on it, though:
>
>    1. I assume *lazyload* on a link tag won't block rendering either, but
>    it's not explicitly stated.
>    2. If a page holds multiple link tags to stylesheets, and some of them
>    have the *lazyload* attribute, what's the cascading order? Is it in
>    the order of appearance in the DOM, or the order in which they were
>    processed (I.e. The lazy loaded ones are last). Also, what's the cascading
>    order between multiple lazy loaded stylesheets? This seems to be addressed
>    for links, since as soon as ordering is needed, lazyload is ignored.
>    3. I assume postpone and lazyload objects don't delay DOMContentLoaded
>    either? Is there a requirement to not download a lazy-loaded resource until
>    DOMContentLoaded has been fired?
>    4. What effect can (inline or not lazy-loaded) scripts in a page can
>    have on lazy loaded resources? I.e. Can a script interrupt a lazy loaded or
>    postponed download, for instance by hiding it? Would that abort the
>    request? What's the effect of a script removing the lazyload or postpone
>    attribute? The answer to some of these may be fairly obvious (to me, at
>    least), but I think it'll be good to define these behaviors in the spec.
>    5. I assume this replaces the img defer attribute? (
>    http://lists.w3.org/Archives/Public/public-web-perf/2013Apr/0063.html)
>
> Cheers,
> Guypo
>
> --
> Guy Podjarny | CTO, Web Experience, Akamai
>
Received on Thursday, 26 September 2013 05:12:45 UTC

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