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Re: [client-hints] new v1 spec draft and src-N interop

From: Darrel O'Pry <darrel.opry@imagescale.co>
Date: Thu, 31 Oct 2013 19:18:56 -0400
Message-ID: <CAGfUJnMdK3a6AUsyq62sg8+acO3cwBhwOsWvpkuSynTJpfZ6vw@mail.gmail.com>
To: Ilya Grigorik <igrigorik@google.com>
Cc: "public-respimg@w3.org" <public-respimg@w3.org>
Awesome spec. It can't be easy to write those things.

What is CH-RW exactly? Is it the size the image is intended to be displayed
at or the width of the browser / device? I read it as the former, which
made me curious if the browser needs to finish calculating the layout
before it can begin fetching images?

On Thu, Oct 31, 2013 at 5:41 PM, Ilya Grigorik <igrigorik@google.com> wrote:

> The goal of Client Hints is to automate (where possible) the negotiation
> of optimal resolution and size of delivered image resources.
> - For a quick intro: https://github.com/igrigorik/http-client-hints
> - New v1 draft:
> https://github.com/igrigorik/http-client-hints/blob/master/draft-grigorik-http-client-hints-01.txt
> - For server folks (or if you want to see it in action):
> https://github.com/igrigorik/http-client-hints/tree/master/server
> With that in mind, a quick overview of differences from previous draft:
>    - Hints are sent in different headers (e.g. CH-DPR: 2.0) - this allows
>    better interop with existing caches [1]
>    - New "server confirmation" header (e.g. "DPR: 1.5") allows server to
>    indicate the DPR of served resource, which is then used to adjust intrinsic
>    size calculations on the client. [2]
>    - "Device width" has been replaced with "Resource display width" (in
>    DIPs) [3]
> Also, I've added a section on interop with src-N (see [4]) to demonstrate
> how CH and src-N can work together to simplify the various RICG use cases.
> That said, note that the choice of using/not-using either src-N and/or CH
> is completely up to you. You can combine both and get the benefit of
> automation of CH + art-direction of src-N, or, you can use src-N for
> everything, or, you can just use CH to automate resolution switching (viar
> CH-DPR hint) and resizing (via CH-RW hint).
> Finally, we have a CH prototype in Chrome that you can play with, check
> out the instructions here:
> https://github.com/igrigorik/http-client-hints/tree/master/server#client-hints-clients
> Feedback, suggestions, questions, etc.. all welcome!
> ig
> [1] https://github.com/igrigorik/http-client-hints/issues/14
> [2] https://github.com/igrigorik/http-client-hints/issues/13
> [3]
> https://github.com/igrigorik/http-client-hints/blob/master/draft-grigorik-http-client-hints-01.txt#L239
> [4] https://github.com/igrigorik/http-client-hints#interaction-with-src-n

Darrel O'Pry, engineer
ImageScale.co, Images for the Responsive Web
http://imagescale.co/#join <http://www.spry-group.com/>
Received on Thursday, 31 October 2013 23:19:43 UTC

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