Light beam still visible when laser is hidden

[arouinfar]

Discovered while reviewing the phetioFeatured overrides for #305. Semi-related to #296.

If you set view.lightNode.visibleProperty to false while the light is on, the laser is hidden but the beam is still visible. This looks buggy to me.

Should we update model.light.isOnProperty to hide the beam in this situation? Clients would need to turn the light back on when they make the laser visible in the view again, but that seems reasonable.

[pixelzoom]

In general, I'm not a fan of visibleProperty having side-effects like you've proposed. Could we just make view.lightNode.visibleProperty be phetioReadOnly: true? Is there any reason why the light should be hideable? This screen seems totally useless when there is no light.

[arouinfar]

Good point @pixelzoom. If clients want to prevent students from turning on the laser, they should just hide its on/off button. Let's make view.lightNode.visibleProperty be phetioReadOnly: true and phetioFeatured: false. I'll take care of the latter, back to you for the former.

[arouinfar]

Updated the overrides in the above commit.

[pixelzoom]

It occurred to me that we typically only instrument visibleProperty with phetioReadOnly: false when the visibility can actually change, and there's some value in the client being able to see if it's changed. That's not the case here, so I uninstrumented lightNode.visibleProperty (via option phetioVisiblePropertyInstrumented: false) and it therefore no longer appears in Studio or the API.

Back to @arouinfar for review.

[arouinfar]

Thanks @pixelzoom. The tree looks good, closing.