[webkit-help] Force Click events

Benjamin Poulain benjamin at webkit.org
Thu May 7 13:21:27 PDT 2015

Hi Jon,

Beth does not participate on webkit-help. Can you move this discussion 
to webkit-dev?

I have one answer below. Beth can better answer the technical questions.

On 5/7/15 1:17 AM, Jonathan Rimmer wrote:
> On Twitter, I was bemoaning the lack of communication re. the recently
> added Force Click events to Benjamin Poulain, and he suggested, probably
> correctly, that I am out of the loop with respect to WebKit development.
> There had, he said, been dicussion of this feature on the mailing lists,
> bugzilla, and the recent contributors meeting.
> This therefore, is my attempt to get in the loop on this issue. I was
> wondering if anyone could help me find the following:
> Mailing list posts: I have tried searching with the Gmane archive, but
> have been unable to find any dicussions on this issue. It doesn't help
> that Gmane does not support phrasal searches, meaning I cannot easily
> search for "force click", "force touch", "pointer events", etc. Can
> anyone suggest what words I should search for, or direct me to the
> relevant threads?
> Contributors meeting: There was apparently a 1 hour discussion at the
> contributor's meeting that lead to the agreement that the Force Click
> experiment should be upstreamed. Is there a video or sound recording of
> this dicussion available? Is there a set of minutes or other summary
> available? A blog post?
> Documentation: Benjamin said the feature has been upstreamed to gather
> feedback. Can anyone point me to developer documentation that would
> assist in using/testing the feature? Or something like the Surfin'
> Safari blog posts that introduced the CSS gradient feature?[1]
> I am also curious about the decision to develop a non-standard feature
> instead of implementing Pointer Events? The Point Events spec defines a
> "pressure" property on pointer events that seems analagous to the
> "force" property introduced by this feature. Why was a proprietary
> solution pursued instead of adopting the W3C standard? What does the
> Force Click events offer that Pointer Events do not?

You probably misunderstand what force click is. It is a second level of 
click as you keep pressing on a trackpad (it is a "deeper" click). The 
animations between the first and second clicks are driven by the 
difference of pressure between the two.

Pointer Events does not have any semantic that work with force click. 
The "pressure" property on PointerEvent is pretty much useless in this 

To make things worse, the way it was spec'ed does not correspond to the 
way the hardware works.

> Also, how does the development of this feature relate to the WebKit
> project's stated goal of standards compliance? [2]. Is there a plan to
> standardise this events with the W3C? Is it wise to name this feature
> after a marketing term used by a single contributor organisation? Is it
> intended that these features will be interopable with pressure-sensitive
> hardware other than Apple's Force Touch trackpad?
> [1] https://www.webkit.org/blog/175/introducing-css-gradients/
> [2] https://www.webkit.org/projects/goals.html
> Thanks,
> Jon
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