Both individual hands should show Interactive Highlights with multitouch

[zepumph]

The work would be done in phetsims/scenery#1367, but it would be good to have a sim-specific issue to track this. Here is the highlight design for multi-touch:

@emily-phet, today during our RAP meeting, @terracoda and I were wondering if this is blocking ratio and proportion. Can we publish RAP without this feature?

[terracoda]

I think this issue is deferred for now.

[Nancy-Salpepi]

@zepumph @terracoda I have a question about this for phetsims/qa#863:
I know only one hand has the interactive highlight, but if I move both hands at the same time what should voicing say? I would have thought the responses would give the positions of both hands, but it only gives the location of the hand that is highlighted even though both were moved. Is that what is expected right now?

multitouchVoicing.mov

[terracoda]

Nice catch @Nancy-Salpepi . Though we do have a description design for using the Both Hands interaction for with bi-manual input while using a keyboard, we were not able to make these descriptions work for bi-manual input on touch devices.

I can't remember exactly why, but maybe something to do with only one touch event at a time. I think the first finger that goes down will get the interactive highlight and the last finger that comes up will get described with the indy-hand slider descriptions.

[Nancy-Salpepi]

Thanks for explaining @terracoda!

[terracoda]

To get the "Both Hands" descriptions for mouse and touch, you need to use the Lock Ratio checkbox.