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

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. 

> 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.

James