[pointerevents] Normatively make touch-action apply for direct-manipulation pen devices

RByers has just created a new issue for https://github.com/w3c/pointerevents:

== Normatively make touch-action apply for direct-manipulation pen devices ==
We have this note at the top of [section 9](https://w3c.github.io/pointerevents/#declaring-candidate-regions-for-default-touch-behaviors):

> While the issue of pointers used to manipulate the viewport is generally limited to touch input (where a user's finger can both interact with content and pan/zoom the page), certain user agents may also allow the same types of (direct or indirect) manipulation for other pointer types. For instance, on mobile/tablet devices, users may also be able to pan using a stylus. This section applies to these scenarios as well (despite the specification's use of "touch").

We discussed [the PR](https://github.com/w3c/pointerevents/pull/188) a bit [on Twitter](https://twitter.com/patrick_h_lauke/status/841028283533799425).  I think there should be normative text that REQUIRES that touch-action apply to a device if and only if  [InputDeviceCapabilities.pointerMovementScrolls](https://wicg.github.io/InputDeviceCapabilities/#dom-inputdevicecapabilities-pointermovementscrolls) is true.

In particular, I think doing anything else would cause a web compat and interop problem.  Eg. if we decided to change ChromeOS so that pen dragging scrolled but DIDN'T honor touch-action, then tons of sites like Google Maps would be broken when you drag with pen (since you'd get a pointercancel).

The simplest way to do that is to probably refactor the text at the top of [10.3](https://w3c.github.io/pointerevents/#implicit-pointer-capture) into a section that defines the term "direct manipulation pointing device", and then reference that term from both the touch-action and implicit capture sections.

@patrickhlauke @mustaqahmed @NavidZ WDYT?

Please view or discuss this issue at https://github.com/w3c/pointerevents/issues/202 using your GitHub account

Received on Friday, 5 May 2017 18:14:53 UTC