Re: [pointerevents] Add support for laptop touchpads responding to the `touch-action` prop (#478)

Just wanted to chime in as a Firefox engineer: if the intent of the spec is that `touch-action` **should** apply to touchpads, I don't think that's sufficiently clear in the current spec text (and indeed, none of the three major browser engines seem to have interpreted it that way so far).

The only place touchpads are mentioned in the spec is this note:

> In some cases, touchpads (like those found on a laptop) will allow the user to scroll by "dragging" on the touchpad. However, this is generally achieved by the touchpad generating "fake" mouse wheel events, so this wouldn't count as a direct manipulation.

Here's what touchpad scroll and zoom gestures currently produce:

 * At the UI toolkit level (what the browser implementation sees), they generally produce some sort of "touchpad scroll" or "touchpad zoom" events.
   * These are distinct from events produced by a click-wheel mouse, and have more granular deltas.
   * But they're also distinct from `touch` events, in that we don't have information about the individual touch points (and even if we did, those touch points would not have a direct correspondence to points on the page the way they would in case of a touchscreen).
 * At the web content level (what the page sees), they produce `wheel` events (with the Ctrl modifier set in the case of zoom gestures); one might describe these as "fake" in the sense that no actual mouse wheel was used (nor Ctrl key pressed).

Given the above, it's not clear to me whether such events should be considered "direct manipulation".

If that's the intention, I'd like to suggest:
 * Making this more explicit in the spec.
 * cc'ing relevant Blink and Webkit engineers on this issue to make sure they're on board with this direction, so that in implementing this in Firefox we can be confident we're not introducing compat issues

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Received on Monday, 16 October 2023 23:30:40 UTC