Re: Several event types are too discrete to be useful for touchscreen input

On Mon, Nov 5, 2012 at 5:43 PM, James Craig <jcraig@apple.com> wrote:

>
> On Nov 5, 2012, at 12:44 PM, Rick Byers <rbyers@chromium.org> wrote:
>
> Great, thanks!  Sorry I'm not up-to-date on the minutes of this group (I
> actually can't find the specific minutes you're referring to -
> http://www.w3.org/WAI/IndieUI/wiki/Meetings/TPAC2012#Minutes says they're
> TBD).
>
> Is there a good reason to prefer polar co-ordinates to
> cartesian co-ordinates?
>
>
> Not really. A lot of times the particular language used when creating
> actions gets changed by the time it makes it into the spec. Some of the
> discussion was leading towards directional events, but when we decided that
> wouldn't be enough, polar coords was suggested.
>
> If the goal is to enable apps to use these events instead of mousewheel,
> it would help in adoption to have the co-ordinate system be the same (and
> seems like most real use cases would end up having to convert to delta-X
> and delta-Y values anyway).
>
>
> Sure that sounds reasonable, and as you note, probably easier on authors.
>

Great, thanks!

> Ok, so how about UIValueChangeRequestEvent then?  The spec mentions
> "gestures on touch-enabled interfaces" as one of the scenarios.  Should it
> also change to use some sort of continuous value instead of the four
> different delta amounts specified by the enum?
>
>
> That depends. I think this would require more introspection into the type
> of control and allowed values. For example, should a slider (input
> type="range") value adjust by 1.0? By the minimum step value? What about
> values on custom controls? Custom controls are the scenario this event was
> intended for, and there is no way for a UA to determine acceptable values
> on controls of unknown types. Presumably this could be defined in ARIA
> attrs like valuemin, valuemax, and (newly proposed) valuestep.
>

Yeah, I was wondering about the use cases here and how much the UA would
know.  I was assuming the UA would at least know, for example, the size of
a control in pixels against which to measure a drag gesture on a touch
screen (eg. so it could say increase to 20% of max) but I guess that's
assuming too much about the type of control.  Anyway I'm not personally
particularly concerned about this scenario.

James
>
>