WavelengthSlider: support UV and IR wavelengths

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In models-of-the-hydrogen-atom (MOTHA), we need a wavelength slider that supports UV wavelengths. It looks like this in the Java version:

PhET has scenery-phet.WavelengthSlider, but it only supports visible wavelengths. It looks like this:

Is a need for IR wavelengths anticipated in any upcoming or future sims?

We could either enhance WavelengthSlider (preferred) or create something new.

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MOTHA also needs to decorate the spectrum (slider track) with vertical lines that denote the absorption wavelengths. Here's what that looks like in the Java version. Note the vertical black lines at the left end of the spectrum.

But before implementing that, we should verify that these lines are effective. Imo, they are difficult to see and use, so they might be revisited as part of the sim refresh (see phetsims/models-of-the-hydrogen-atom#1).

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In Java, piccolophet.WavelengthControl handled "visible wavelengths, plus optional UV and IR wavelengths". In MOTHA, it was extended in GunWavelengthControl. So I would investigate adding features to scenery-phet.WavelengthSlider.

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This issue is very low priority, since I'm unlikely to get to MOTHA development until Fall 2016. Unassigning until then.

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Well, it's MOTHA time, so I guess I'll need to do this. Self assigning.

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Consider renaming WavelengthSlider, since it's not just a slider, it also has tweaker (arrow) buttons. Convention suggests that this should be named WavelengthControl, which was in fact the name of the Java implementation.

If renamed, it would also make sense to move this to the "Components" screen in scenery-phet demo.

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In order to add support for UV and IR wavelengths to WavelengthSlider, we'll need to add this support to SpectrumNode, which renders the slider track. See Java implementation at edu.colorado.phet.common.phetcommon.view.util.SpectrumImageFactory.

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Deferred until work resumes on MOTHA, probably sometime in early 2017.

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MOTHA keeps getting pushed out into the future, currently looking like late Summer or Fall 2017 before work resumes on it. So I'm going to unassign this issue until then.

[samreid]

Please see related work on WavelengthSlider in #371 (comment), particularly this comment:

But hopefully none of these changes make it difficult to add UV and IR to WavelengthSlider, as is required for #211 (needed by MOTHA).

I introduced a new type SpectrumSlider which takes a min value, max value and color mapping function. I expect it would make it easier to add UV and IR. For instance, in the visible range, you would return VisibleColor.wavelengthToColor(), and in the UV range you could return Color.gray. You could even use that function to add the vertical lines, if they are still desired. The trick will be adding the text in the track--we may wish to add getter for the track node to make that easy, or a add/removeTrackChild method on SpectrumSlider.

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Un-deferring and self assigning. This is needed for MOTHA, which has resume development.

Labeling this as a proposed "epic" for Q3 2022.

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MOTHA is on hold indefinitely, so this issue is no longer a priority. Unassigning until MOTHA is scheduled.