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Re: Touch and gestures events

From: Garrett Smith <dhtmlkitchen@gmail.com>
Date: Tue, 13 Oct 2009 17:40:23 -0700
Message-ID: <c9e12660910131740p2439a88bl73cc3fa515749d3a@mail.gmail.com>
To: Olli Pettay <Olli.Pettay@helsinki.fi>
Cc: www-dom@w3.org, WebApps WG <public-webapps@w3.org>
On Wed, Jun 17, 2009 at 1:22 PM, Olli Pettay <Olli.Pettay@helsinki.fi> wrote:
> Hi all,
>
> there seems to be some interest to standardize touch and gesture events.

Please provide links to where interest was indicated.

Especially valuable are where mobile companies have provided
information about the hardware technology and how it relates to the
touch evetns API.

> They are becoming more common on OS level: Windows 7 has them, iPhone has
> them, OSX has at least gestures, X is getting support for them etc.
>

Can Touch and Gesture events be separated, or are they necessarily coupled?

> So perhaps there should be a new spec for touch and gesture events.
> Hopefully a pretty simple spec.

Would it be simpler to have a touch events as a stand-alone standard?

>
> It is not yet quite clear what the events should look like, but maybe
> something like this:
>
> interface PointerEvent : UIEvent {
>        readonly attribute long streamId;
>
>        readonly attribute long screenX;
>        readonly attribute long screenY;
>
>        readonly attribute long clientX;
>        readonly attribute long clientY;
>
>        readonly attribute boolean ctrlKey;
>        readonly attribute boolean shiftKey;
>        readonly attribute boolean altKey;
>        readonly attribute boolean metaKey;
>        void initPointerEvent(...);
> };
>
> interface TouchEvent : PointerEvent {
>        readonly attribute float pressure;
>        readonly attribute long size;
>        void initTouchEvent(...);
> };
> Touch Event types: touchdown, touchmove, touchup, touchover, touchout
>

A blatant violation of US Patent: US20090225039.


>
> Touch Event handlers might want to know all the current touch positions, but

The Event instance does not need to know the current touch positions,
but the callback does. The current event positions could easily be
stored in a place where they can be polled, either on the Event, a
View, or some other object.

> even then, all the events should be dispatched, so that
> events propagate properly also for example through (XBL2) anonymous content.

For those of us who are unfamiliar with how events are propagated with
XBL2 anonymous content, can you please explain?

> Perhaps defaultView (window) could have a property which lists
> current touches.

This allows the callback to check that property (currentTouches, or
whatever), on window.

(I don't like iPhone's touch events which contain all sort
> of list of touches.)
>
No, fortunately that API is patented so it won't be usable (and hence,
will not be used as a public standard).

The legality of that Patent seems questionable, however. Itself
borrows from existing D3E API and idiom, so it is not completely
original.

> Gesture Events have the problem where to dispatch the events. Should
> gestureStart be dispatched to the same node as gestureEnd? What if the node
> is removed, or moved to another document? User is still doing the gesture,
> so the event should be dispatched to somewhere. Where should other gesture
> events be dispatched? Whatever is "under the gesture"?
>
> Any comments, ideas?
>
Apple has patented Touch events under US Patent: US20090225039.

I do not mind the innovation so much, but the fact that it is
proprietary leads to difficulty for cross-device scripting. If the
proliferation of touch screen devices were matched 1:1 with
proprietary touch event API, the result will be greater divergence
than was seen during the Great Browser Wars.

(I see Palm now has constant Event.MOUSE_DRAG).

Has it been so long since the Browser Wars of IE and Netscape that the
lesson has been forgotten? Were the consequences not understood deeply
enough?

Perhaps Maciej or other Apple developers can comment on some of the following.

* initTouchEvent takes 18 parameter variables. Three of these
variables are "TouchList" variables. Each TouchList is comprised of
one or more Touch instances. Was a simpler API considered?

* the TouchEvent payload for the eventListener does not have the
interesting data itself. Instead, the interesting data is on the
"changedTouches" TouchList. The callback must address this complexity
by hanling not only a touch event, but a touch event which is not
directly useful (the information the program needs is in the touches
or changedTouches).

I would like to see input from Palm, RIM, Opera, and other developers
of mobile browsers and touch screen devices on this thread.

Garrett
Received on Wednesday, 14 October 2009 00:41:00 GMT

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