Bug 20109 - Permitted values for pressure

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.

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 ***

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