RE: Agenda August 18th

Thanks Patrick!  We will review this in today's call.

I appreciate you adding this.

Best,

Kathy
CEO & Founder
Interactive Accessibility
 
T (978) 443-0798  F (978) 560-1251  C (978) 760-0682
E kathyw@ia11y.com  
www.InteractiveAccessibility.com
 
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-----Original Message-----
From: Patrick H. Lauke [mailto:redux@splintered.co.uk] 
Sent: Thursday, August 25, 2016 4:31 AM
To: public-mobile-a11y-tf@w3.org
Subject: 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-measu

> rements-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-B417-0

> 265B808CD06/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


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Patrick H. Lauke

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Received on Thursday, 25 August 2016 13:34:53 UTC