Create 2 jumping Keyboard Shortcuts for the grabbed ruler

[terracoda]

In issue #134 we decided that the following 2 "jumping" keyboard shortcuts for the ruler interaction would be helpful:

• [J] + [C]: where C represents a centers of spheres. A shortcut combination to measure distance between the centers of the mass spheres. Pressing J+C when the ruler is grabbed would place the zero mark of ruler at the center of the m1 sphere, and a context response would read out the distance between the spheres and the new location of the ruler.
• [J] + [H]: where H represents Home position for the ruler. A shortcut combination to release the ruler and return the ruler to its home position just below the sphere position sliders.

For more details see the Measure Distance button in the Control Area of the PDOM section and the Interaction & Design Details for the Measure Distance button.

Edit Oct 18, 2019:

• Changed shortcut from J plus S to J plus C.
• Provided new link to design doc

[terracoda]

@zepumph, this is a new issue so assigning to you, but no rush as you transfer over to this sim.

[zepumph]

For now I'm going to try to keep only high priority issues assigned to me to keep a better todo list; as such unassigning for now.

[zepumph]

On hold until #140 is sorted out.

[terracoda]

@zepumph, since this has to do with ruler, I think it can be put on hold until quarter 4.

[terracoda]

@zepumph, I think J plus C is going to be a better shortcut than J plus S.
I think C speaks more to aligning the ruler to measure the distance between the centers of the spheres.

I don't think you have implemented these shortcuts yet, but we do have them them in them noted Keyboard Shortcuts.

In addition to implementing J plus C as the Shortcut, please be sure to update:

• Visual Keyboard Shortcuts
• A11y content for Keyboard Short cuts

[zepumph]

@terracoda I implemented this above. You can either review this piece now, or perhaps wait and do everything together. One question I had was about the ordering of hotkeys. I found that this doesn't work when I hold 'H' and then hold 'J'. Is that expected?

[zepumph]

@terracoda noticed that sometimes you have to press the hot keys more than once to get them to fire. For example in the following sequence, I reliably needed to press "J + C" twice, only the second time did it move:

J+C
J+C
J+H
Enter (to grab again)
. . .

[zepumph]

• I also need to implement the alerts from jumping.

[zepumph]

I also need to implement the alerts from jumping.

Today, @terracoda said she would look over things, and then let me know when these jumping alerts are ready for implementation. Unassigning until then.

[terracoda]

@zepumph, apologies for the delay. I reviewed and tweaked a couple of the phrases in the tables. The responses (alerts) are ready to go.

[zepumph]

There have been implemented (I think) as we want them, but because of #189, they aren't yet working. I'm going to head over there now.

[zepumph]

Oops, I was adding the wrong utterance to the queue. These should be working now. @terracoda this is now ready for review.

[terracoda]

@zepumph, these shortcuts work and sound great!
I checked off #138 (comment)

Sounds like it is done to me. Nice work!