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Re: [css3-values] recommendation for pixel units

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 20 Mar 2013 15:49:22 -0700
Message-ID: <CAAWBYDDuMFQ1MY+XPxngJDnRBragBj_G5Nf3SCvzsM2P8tVJwQ@mail.gmail.com>
To: James Holderness <j4_james@hotmail.com>
Cc: www-style list <www-style@w3.org>
On Wed, Mar 20, 2013 at 1:08 PM, James Holderness <j4_james@hotmail.com> wrote:
> In section 5.2, with regard to lower-resolution devices, and devices with
> unusual viewing distances (which I assume would include most mobile
> devices), it is recommended that the pixel unit refer to the whole number of
> device pixels that best approximates the reference pixel.
>
> I take that to mean it is recommending that the device-pixel-ratio should
> always be a whole number. Am I reading that correctly?
>
> If so, is this perhaps worth reconsidering, given that it's not uncommon
> these days for mobile devices to default to a device-pixel-ratio of 1.5 or
> 0.75?
>
> I realise this text has been in the spec since the beginning of time, but if
> implementers don't think it makes sense anymore, and are just going to
> ignore it, is there any point in continuing to make the recommendation?

It generally *is* a good idea to have the px be an integer number of
device pixels.

However, a lot of devices have found it even more valuable to set the
ratio to whatever makes their screen 320px wide, to match the iPhone.
That's fine, but it doesn't negate the original reasoning.  Those
devices just believe (likely with good reason) that it's better to
have slightly worse display in exchange for poorly-authored mobile
sites working correctly.

Other high-DPI devices like laptops, though, have continued to use an
integer number of pixels, as the large-screen ecosystem isn't
dominated by poorly-authored sites that assume a single precise pixel
width.

~TJ
Received on Wednesday, 20 March 2013 22:50:09 GMT

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