[webkit-dev] Force Click events

Maciej Stachowiak mjs at apple.com
Fri May 8 21:08:02 PDT 2015

Beth gave a bunch of details of the feature, but I would like to expand a bit on our standards plans, and cross-platform potential of this feature:

(1) We definitely plan to take this proposal to standards bodies. We decided to implement a prototype first, so we could ensure we have something that makes sense, because this is a complex area.

(2) We’re not necessarily set on “force" as the term to use instead of “pressure”. We’re open to changing this depending on what the standards community thinks. We did think about alignment with pointer events, but force has the advantage of brevity and also of working better in names of the new events like “mouseforcedown” (“mousepressuredown" would sound weird). Also, I find that discussing force vs. pressure tends to start physics arguments about whether the hardware in relevant input devices is actually measuring Pascals (pressure) or Newtons (force). Force is just our placeholder choice.

(3) Pointer Events don’t actually provide everything needed to make best use of the Force Trackpad. One notable feature of the device is that, by convention, it supports two levels of press, each with a haptic. We thought the “deep press” was worthy of its own set of events.

(4) We did not want to make Pointer Events a prereq for making use of pressure. First, we don’t want to require web developers to change event models to get new functionality, and second, we’re not entirely sure we support the idea of combining mouse events and touch events into one concept. We are fine with adding the same functionality to Pointer Events, of course, and would even recommend that.

(5) It’s not our intent to make our event extensions specific to Apple hardware. However, the force trackpad does have interesting features beyond pressure-sensitivity. In particular, it has a software-controlled haptic for click and by convention has two levels of clicking. We would like events that support this well, but are also reasonable for hardware without these specific features.


> On May 8, 2015, at 3:25 AM, Jonathan Rimmer <jon.rimmer at gmail.com> wrote:
> [I originally posted this to webkit-help, but Benjamin suggested suggested I post here instead]
> Hi all,
> 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?
> 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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