[pointerevents] Clarify/expand introduction to the touch-action section (#366)

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

== Clarify/expand introduction to the touch-action section ==
Currently, the "Declaring candidate regions..." section starts with

>For touch input, the default action of any and all pointer events MUST NOT be a manipulation of the viewport (e.g. panning or zooming).
>Touch manipulations are intentionally not a default action of pointer events. Removing this dependency on the cancellation of events facilitates performance optimizations by the user agent.

This could do with being expanded a bit, as it may not be immediately obvious to a layperson what this *actually* means ... that cancelling a pointer event (with `preventDefault()` for instance) can't be used to stop/suppress scrolling or zooming, the same way that, say, this can be done with touch events. And that *that* is also the reason why you need to use `touch-action` instead to declaratively say whether or not the user agent can do scrolling/zooming or not (since you can't prevent it from the event handler).

Just an extra sentence or so that explains this would help make this fact more immediately clear, and give some context that then leads naturally into the meat of this section.

Suggest tackling this *after* https://github.com/w3c/pointerevents/pull/350 lands

Please view or discuss this issue at https://github.com/w3c/pointerevents/issues/366 using your GitHub account

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Received on Sunday, 18 April 2021 16:08:32 UTC