Re: Agenda August 18th

For info, I've added some of the notes below to 
https://www.w3.org/WAI/GL/mobile-a11y-tf/wiki/Proposed_SC_Target_Size#Evidence

P

On 18/08/2016 21:37, Patrick H. Lauke wrote:
>
>
> On 18/08/2016 18:16, David MacDonald wrote:
>> Kathy has asked us to review the size of activation SC. We currently
>> have 44px as a placeholder, but apparently Google is 48px and Apple is
>> 44pt.
>>
>> I think points=1.33 x 1px, which is 57px (1)...
>
> That's incorrect. When Apple talk about points in their guidelines,
> they're not referring to CSS points. Apple use "points" as an
> density-indepent unit of measure. 1pt = 1 physical pixel on a non-retina
> display, 1pt = 2 physical pixels on a retina display. As we use CSS
> pixels instead, and since these already adapt to different device
> density when using the ideal viewport, 44 CSS pixels is the measure that
> Apple's guidance translates to.
>
> Apple, in their wisdom, make it exceedingly difficult to actually find
> this in their documentation, but see for instance
> http://ivomynttinen.com/blog/ios-design-guidelines which outlines the
> meaning of "points" when Apple use it (because having 2 different types
> of "points" - the typographic print measure and the CSS one - wasn't
> enough and we needed a third one).
>
> Now, for completeness, Google uses "dp" (density independent pixels), so
> their actual guidance is 48dp x 48dp. However, as noted on
> https://material.google.com/layout/units-measurements.html#units-measurements-density-independent-pixels-dp
> "When writing CSS, use px wherever dp or sp is stated. Dp only needs to
> be used in developing for Android", so yes we're treating it as 48px x
> 48px.
>
> As additional data points, Microsoft's Design Language documentation
> uses "EF" (effective pixels) as a similar density-independent unit of
> measure
> (https://msdn.microsoft.com/en-us/windows/uwp/layout/design-and-ui-intro#effective-pixels-and-scaling).
> For touch target sizes, Microsoft recommends "44 EP × 44 EP is the
> minimum touch target size" (see the PDF
> http://download.microsoft.com/download/F/2/C/F2C19EC6-03E2-4D8C-B417-0265B808CD06/Microsoft-Design-Language-1603.pdf
> - strangely, I can't seem to find the same info in an actual HTML/CSS
> format on the Microsoft documentation site). As "EF" is also only aimed
> at actual native development, we can roughly treat 1EF as 1 CSS pixel
> (looking at some of the typical device screen sizes in the PDF that are
> defined in EF, this makes the most sense).
>
> Incidentally, I'm fairly sure I explained the above (particularly about
> not confusing Apple's "points" with CSS points) at length previously on
> this list (or in a call) somewhere.
>
> I'd be happy to say that in light of Google's slightly higher value, we
> round the whole measure up and call it a nice round 50px x 50px, or meet
> in the middle and say 46px x 46px. Just as long as our rationale for
> doing so is clear.
>
> P


-- 
Patrick H. Lauke

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Received on Thursday, 25 August 2016 08:31:28 UTC