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Re: [mediaqueries4] pointer: coarse and pannable, zoomable viewports

From: Florian Rivoal <florian@rivoal.net>
Date: Wed, 12 Dec 2012 20:36:21 +0100
To: www-style@w3.org, "Edward O'Connor" <eoconnor@apple.com>
Message-ID: <op.wo7x2vnpf5de51@localhost.localdomain>
On Wed, 12 Dec 2012 18:10:13 +0100, Edward O'Connor <eoconnor@apple.com>  
wrote:

>> Typical examples of a ‘fine’ pointing system are a mouse, a track-pad
>> or a stylus-based touch screen. Finger-based touch screens would
>> qualify as ‘coarse’.
>
> Presumably, touch screens whose Web views operate as pannable, zoomable
> viewports (like on iOS) are intended to match 'pointer: coarse'. But the
> user can make very fine-grained touches simply by zooming the viewport.
>
> Is such a UA expected to match 'pointer: fine' when zoomed in, and
> 'pointer: coarse' otherwise? I hope not; I'm not enthusiastic about
> triggering layout on zoom. If such a UA never matches 'pointer: fine'
> but only 'pointer: coarse', it's more likely that page authors will use
> this MQ to make content that behaves poorly when the user is zoomed in.

This may not be clear from the wording in the spec, but the intent is that
the UA would decide between coarse or fine based on the accuracy of the
pointer at the native scale. The expectation is that authors would for
example size their click targets based on this information. When the user
zooms in, no change in layout is expected; the MQ stays the same, and the
click targets scale with the rest of the page according to the zoom.

In effect, the MQ does not say that the user will never be able to
click accurately, only that it is inconvenient for him to do so (either
he needs overly careful manipulation of the pointing device, or he needs
to zoom in, or he needs to plug in the optional accurate device...).
Pages authors are expected to react to coarse by designing
pages that do not rely on accurate clicking to be operated.

I have updated the spec to clarify. Let me know whether this addresses
your issue.

  - Florian
Received on Wednesday, 12 December 2012 19:33:12 GMT

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