let's bump to 10mm from 9mm

I'm thinking we should bump it to 10mm and remove the "one dimension" part.
I think we can delete 2.5.4 (or collapse in 2.5.4, 2.5.5), something like
this...
2.5.5 Touch Target Clearance: The center of each touch target has a
distance of at least 10 mm from the center of any other touch target,
except when the user has reduced the default scale of content. (Level AA)
[MOBILE]

Then the techniques under 2.5.4 can go in here...

   - *[MOBILE] Multiple Elements: *When multiple elements perform the same
   action or go to the same destination (e.g. link icon with link text), these
   should be contained within the same actionable element. This increases the
   touch target size for all users and benefits people with dexterity
   impairments. It also reduces the number of redundant focus targets, which
   benefits people using screen readers and keyboard/switch control.
   - M002 <http://w3c.github.io/Mobile-A11y-TF-Note/Techniques/M002> *Touch
   Target*: Ensuring that touch targets are at least 9mm.

Here's a discussion from a UX site that seems pretty solid ...

"Be sure to check for interference on each axis of a target. To avoid
interference errors, make sure that touch targets are *at least* 8
millimeters apart on center—with 10-millimeter spacing being strongly
preferable. *On center* is an engineering term that means when measured
from the center of each touch target. In this way, you can be measure the
distance between the centers of differently sized objects such as a link
and a button, because neither the visual- nor the touch-target sizes matter
in this measurement.

As a consequence, most touch targets will never be too closely adjacent to
each other, and only small amounts of space are necessary between them.
This space does not have to be visually apparent. A non-touch area need not
necessarily be whitespace. For example, toolbars often comprise icons that
have suitable spacing, but without *any* visual indication of the gap
between them. And the height of a tab bar can be as narrow as you want
visually, as long as no other targets are too close either above or below
the tabs.

http://www.uxmatters.com/mt/archives/2013/03/common-misconceptions-about-touch.php#sthash.sfRgVb65.dpuf

Cheers,
David MacDonald



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