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Re: [css3-images][css4-images] Replace 'dppx' with 'x'?

From: Simon Fraser <smfr@me.com>
Date: Thu, 14 Jun 2012 22:02:30 -0700
Cc: Florian Rivoal <florianr@opera.com>, www-style@w3.org
Message-id: <1B12376D-F2F0-4FC5-9662-1BA7DACABE7A@me.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
On Jun 14, 2012, at 12:18 PM, Tab Atkins Jr. wrote:

> On Thu, Jun 14, 2012 at 11:25 AM, Simon Fraser <smfr@me.com> wrote:
>> On May 29, 2012, at 4:22 PM, Tab Atkins Jr. wrote:
>>> On Tue, May 29, 2012 at 1:08 AM, Florian Rivoal <florianr@opera.com> wrote:
>>>> On Fri, 25 May 2012 20:07:53 +0200, Christoph Päper
>>>> <christoph.paeper@crissov.de> wrote:
>>>>> Of course, all the reciprocal length units are plain stupid and
>>>>> unnecessary – and always have been.
>>>>> 
>>>>>  image-resolution: <count> [ / <length> ]?;
>>>>>  image-resolution: 1dot; /* with 1px default */
>>>>>  image-resolution: 300dot/1in;
>>>>>  image-resolution: 100dot / 1mm;
>>>> 
>>>> I wasn't there when you initially suggested that, but I think I like it. It
>>>> may be too late to introduce something like that, but I wouldn't mind being
>>>> proven wrong about this.
>>> 
>>> The 'image-resolution' property was reverse-implemented based on what
>>> already existed, so we can't remove what exists, but we can always add
>>> more syntax later.  However, I don't think adding ratios for
>>> expressing resolution is a good thing unless we do it everywhere.
>> 
>> My problem with the dppx unit is that the ratio of device pixels to CSS pixels only makes
>> sense when the page is unscaled. Most mobile devices (and, increasingly, desktop browsers)
>> present pages at a non-unit scale, and allow users to zoom the page in and out. When zoomed,
>> there's an additional scale factor applied that needs to be taken into account in the relationship
>> between device pixels and CSS pixels. The 'dppx' unit pretends that such a scale factor does not
>> exist, which is confusing.
>> 
>> In addition, I still think that most authors will interpret "resolution" in terms of physical screen size,
>> not the 1:96 fixed CSS inch:pixel ratio.
>> 
>> Both are strong arguments for a simple multiplier factor in media queries, as used by device-pixel-ratio.
> 
> You're saying that the value of device-pixel-ratio is sensitive to
> zoom?  So that on a high-res (2x) phone viewing a page that is also
> initially viewport-zoomed to half its size, the device-pixel-ratio is
> 4?

No, device-pixel-ratio is not sensitive to zoom. It's just a statement about the device.
It's only ever 1 or 2 on currently shipping hardware.

Simon
Received on Friday, 15 June 2012 05:03:03 GMT

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