Re: let's bump to 10mm from 9mm

what is 44px on a retina display?

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On Fri, Dec 18, 2015 at 5:21 AM, Patrick H. Lauke <redux@splintered.co.uk>
wrote:

> On 17/12/2015 22:32, Patrick H. Lauke wrote:
>
>> On 17/12/2015 22:06, Richards, Jan wrote:
>>
> [...]
>
>> So 44px was 11 mm on my desktop monitor but 8.5mm on my Samsung Note
>>> phone.
>>>
>>> Maybe the SC wording needs to be more vague and then CSS px and mm
>>> measurements can be offered as sufficient techniques?
>>>
>>
>> I'd be in favor of having the *normative* text be more vague.
>>
>> I fear though that even if it was softened to something like "must be at
>> least as large as an average person's fingertip" (see for instance the
>> note on "Size and positioning of UI" in
>> https://msdn.microsoft.com/en-us/library/windows/apps/hh465370.aspx),
>> the end result is still that there's now a hard requirement to achieve a
>> minimum physical size, but that there's no way for a developer to
>> actually *guarantee* this as they can't check for physical device size,
>> whether or not that device has implemented a sensible device pixel
>> ratio, and they can't test on every possible device out in the wild and
>> coming out in the future. Unless a strong note/exemption can be added
>> somehow to the normative text which puts the onus on device/OS/UA having
>> implemented a sensible mapping?
>>
>> In a further *informative* note we could then provide commonly
>> used/suggested sizes such as 44x44px, and clarify that it may not always
>> be possible for a developer to explicitly know the exact physical size
>> that this will map to, as it depends on multiple factors outside of
>> their control.
>>
>
>
> Having slept on this, I *think* it may be appropriate to to have the
> actual wording of the SC provide a hard value in CSS pixels, e.g. "Touch
> Target Size: One dimension of any touch target measures at least 44px ...".
>
> In the explanatory text, it would then ideally mention that we're talking
> CSS pixels, rather than hardware pixels (with a reference back to CSS 2
> http://www.w3.org/TR/CSS2/syndata.html#length-units); additionally, in
> that text it should clearly state that authors cannot directly control the
> actual physical size that 44px are rendered at on a screen, as this depends
> on hardware/OS/UA, but that 44px was chosen because "generally" it renders
> at an approximate size of 9mm.
>
> This way, the SC is consistently testable (by checking the dimensions in
> CSS pixels), and it clarifies at which point authors are not in control
> anymore of how things are *actually* rendered.
>
>
> P
> --
> Patrick H. Lauke
>
> www.splintered.co.uk | https://github.com/patrickhlauke
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> twitter: @patrick_h_lauke | skype: patrick_h_lauke
>
>
>