clarify what happens if touch-action is changed dynamically

[patrickhlauke]

It's probably implicit in the prose for "9.1 The touch-action CSS property", but: what should happen if, on pointerdown, the touch-action for the element is changed dynamically (for instance, from auto to none, based on the document's scroll position, for a naive pull-to-refresh implementation)? I assume that at that point, it's already too late and the user agent determined what to do (whether to handle the pointer/gesture or not) based on what touch-action was the moment when pointerdown was fired...if so, would it be useful to clarify this in a note?

[patrickhlauke]

Guessing this sentence (as part of the note for the direction-specific pan values) is, essentially, what I'd like to see generalised as a separate note?

It's not possible to change the behavior of a pan in the middle of an operation.

So in essence, that it's not possible to change the behavior of any "gesture" (if that's the most appropriate word) after it has already started (either being handled by browser, or passed on to be handled by JS)

[RByers]

Yep, that's right. I remember bikeshedding about the wording way back. There's a few places this makes it in, but I agree it could be stronger:

When a user touches an element...
... for touches that begin on the element.

If you want to also add an explicit note about this, that's fine with me.