Refine NumberLineSlider instrumentation

[marlitas]

numberPairs.tenScreen.view.numberLineNode.slider.visibleProperty

• This hides more than just the slider - it also hides the number line

numberPairs.tenScreen.view.numberLineNode.slider.thumbNode.visibleProperty

• Rename? This seems like it’s the slider or scrubber. When visible = false, the scrubber hides

numberPairs.tenScreen.view.numberLineNode.slider.trackNode.visibleProperty

• This hides the line, but the tick marks stay.
• I didn’t find a way to hide the tick marks.
• Seems like we’d want to be able to hide the scrubber and the tick marks (independently), but not the line or the counting area
• Probably not useful to disable or hide the number line

[marlitas]

numberPairs.tenScreen.view.numberLineNode.slider.visibleProperty

• I uninstrumented this.

numberPairs.tenScreen.view.numberLineNode.slider.thumbNode.visibleProperty Rename? This seems like it’s the slider or scrubber.

• thumbNode is the terminology we use to refer to this item "scrubber" in common code. Here it is a custom thumbNode but it will be called that in other sims with a slider as well. I would not recommend renaming.

Otherwise I instrumented the number line items to be a bit more intuitive, let me know what you think.

[catherinecarter]

Here are my initial impressions (and will apply to all screens, not just twenty):

• numberPairs.twentyScreen.view.numberLineNode.slider.trackNode.visibleProperty will not be useful
  

• But numberPairs.twentyScreen.view.numberLineNode.slider.trackNode.tickMarks.selfVisibleProperty will be. This is nice. Is it possible to have the end tick marks stay to 'bound' the line to something? The line looks incomplete.
  

Everything else looks great in terms of visible and enabled properties.