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Re: Bug 20109 - Permitted values for pressure

From: Arthur Barstow <art.barstow@nokia.com>
Date: Wed, 06 Feb 2013 06:56:16 -0500
Message-ID: <511244E0.6090004@nokia.com>
To: ext Rick Byers <rbyers@google.com>, Jacob Rossi <Jacob.Rossi@microsoft.com>
CC: "public-pointer-events@w3.org" <public-pointer-events@w3.org>
On 2/5/13 7:58 PM, ext Rick Byers wrote:
> On Monday, February 4, 2013, Jacob Rossi wrote:
>
>     Hey folks,
>
>     We took a second look at this issue and have a suggested tweak to
>     the change we made [1]. In most pen enabled applications, mouse
>     generally emulates /half/ the maximum pressure of pen. As an
>     example, Paint provides half the stroke width when using a mouse
>     as compared with maximum pressure of a pen. This is generally in
>     line with guidance Microsoft has given for pen drawing for quite
>     some time: minimum pressure should be 50% stroke width, half-way
>     pressure is 100% (e.g. what mouse should produce), and maximum
>     pressure is 150% [2].
>
>     Given that, I reactivated this bug for us to consider making the
>     value 0.5 rather than 1 when the device is in the active buttons
>     state.
>
>
> Having the default be intermediate between minimum and maximum makes 
> sense to me, and will probably result in better behaving apps in general.
>
>     Similar to the pressure issue, the spec currently allows
>     implementations to provide a width/height that’s “typical of the
>     device type” when the hardware doesn’t support contact geometry
>     [3]. But it doesn’t require it. IE10 does not simulate
>     width/height for devices that do not provide geometry. But I think
>     we’d probably make IE do so in our next release, similar to
>     emulating pressure. I’d like to consider making the MAY (optional)
>     a SHOULD (recommended) in the spec for emulating width/height. I
>     think the emulation we’d use in IE is:
>
>     Mouse, Pen – 1x1 width
>
>     Touch without hw support for geometry – about 40x40 CSS pixels ***
>
>
> Yes, I like this change (the less UA-defined-behavior the better). Are 
> you aware of any sites today that treat no-radius differently from 
> some reasonable default radius (eg. I could imagine some UI features 
> changing slightly when it's known that radius information is 
> available)? If so then we may need to consider some mechanism to 
> determine pointer capabilities, but without a compelling use case it's 
> probably not worth the complexity.

Thanks Rick.

Jacob - I think we now have sufficient support for your proposal,so 
please implement it.

-Thanks, Art


>     This “smart default” approach should also apply to tiltX/tiltY,
>     but the existing default of 0 seems appropriate for those (e.g.
>     the stylus is normal to the screen).
>
>     -Jacob
>
>     *** Adjusted for zoom. 40 CSS pixels is approximately 11mm, the
>     average width of a touch contact [4].
>
>     [1] http://dvcs.w3.org/hg/pointerevents/rev/47212a0ea91c
>
>     [2] http://msdn.microsoft.com/en-us/subscriptions/cc300776.aspx#S11
>
>     [3]
>     https://dvcs.w3.org/hg/pointerevents/raw-file/tip/pointerEvents.html#widl-PointerEvent-width
>
>
>     [4] http://bit.ly/win8touchguidance
>
Received on Wednesday, 6 February 2013 11:56:28 GMT

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