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Re: [mediaqueries] resolution and device-pixel-ratio

From: John Mellor <johnme@google.com>
Date: Wed, 13 Nov 2013 11:16:31 +0000
Message-ID: <CAG_kaUYXZ3eVHrBKAh9nsqESx0W=GKgDQSKXAUnySrxJ3brKzw@mail.gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: Florian Rivoal <florian@rivoal.net>, "www-style@w3.org" <www-style@w3.org>
Either path seems reasonable, but FWIW resolution is much easier to get
wrong, since (except in print) CSS dpi != physical dpi (which is much less
well known than the fact that CSS in != physical in). So if you copy
(physical) values from mobile device specifications, it's easy to write
incorrect MQs like (min-resolution:320dpi), which the author thinks is
equivalent to (min-resolution:2dppx), but actually corresponds to
(min-resolution:3.33dppx)!

That can probably be solved by developer outreach that recommends dppx, or
recommends dpi for improved backwards compatibility, but explaining that
you should always take the desired dppx value and multiply it by 96, rather
than copying physical values; however I suspect this will remain a source
of errors.


On Sun, Nov 10, 2013 at 5:08 PM, Tab Atkins Jr. <jackalmage@gmail.com>wrote:

> On Sat, Nov 9, 2013 at 7:50 AM, Florian Rivoal <florian@rivoal.net> wrote:
> > During a recent conf call, while discussing the resolution and
> > device-pixel-ratio media queries, it seemed that many people suggested
> that
> > the "resolution" MQ has failed, and that we should pave the cow paths,
> and
> > standardize device-pixel-ratio, possibly as an alias to resolution.
> >
> > Technically, this would not be difficult, but we had explicitly decided
> to
> > do the opposite when we finished MQ3. I am not sure if this change of
> > position reflects a change in opinion across the WG, or merely who was
> > attending this particular conf call.
> >
> > This is what we wrote about it back then:
> >
> http://www.w3.org/blog/CSS/2012/06/14/unprefix-webkit-device-pixel-ratio/
> >
> > Similarly, MDN advises against device-pixel-ratio in favor of resolution:
> >
> https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Media_queries#-moz-device-pixel-ratio
> >
> > As far as I know:
> > Gecko and Blink (and Presto) supports resolution, including the dppx
> unit.
> > IE has it without the dppx unit.
> > Webkit sticks to -webkit-device-pixel-ratio only
> >
> > Resolution is more interoperable than when we chose it as the path
> forward,
> > so I am not sure I understand why this is being reopened.
> >
> > At this stage, I think what is relevant is not some much anyone's (me
> > included) naming preference, but what browser vendors plan to do.
>
> Agreed.  While the support for 'resolution' is relatively recent, it's
> still clearly the interoperable solution now, except for WebKit.  No
> reason to reopen this.
>
> ~TJ
>
>
Received on Wednesday, 13 November 2013 11:17:17 UTC

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