Should dropper be movable?

[arouinfar]

During #117, @kathy-phet and I noticed that the dropper is movable. We don't see any pedagogical value in allowing users to move the dropper, and I couldn't find a reason for it in the design doc. Since the dropper didn't appear in the Java sim, the behavior isn't simply a holdover.

@pixelzoom @ariel-phet do you remember an explicit decision around making the dropper movable? How would you feel about removing the ability to move it?

[arouinfar]

Note that we would need to get rid of view.dropperNode.dragHandler if the dropper isn't movable. (Not sure if that would come for free or not.)

[ariel-phet]

I see no pedagogical reason, it is fairly constrained right now. My guess is people thought it was somewhat more playful. If you or @kathy-phet wants to remove that ability, seems fine by me.

[pixelzoom]

My recollection was that the dropper was made horizontally draggable to make the sim more interactive and fun.

If you want its location to be fixed, its more involved than simply removing its DragListener. The model will also need to be changed. Dropper currently extends Movable, which is where it gets its positionProperty.

If you the fixed position to be something other than the current default, then examine phScale.macroScreen.model.dropper.positionProperty in Studio and tell me what position you'd like.

[kathy-phet]

Then perhaps we just leave it as is. It's not hurting anything. I will note it is not currently possible to make it unmoveable/unpickable without also making the add liquid button unpickable/not working. Let's discuss at an upcoming mini-design meeting.

[pixelzoom]

Also note that the dropper is movable in Beer's Law Lab and Concentration.

Perhaps there should be a general solution for disabling a Node's drag listener?

[arouinfar]

Perhaps there should be a general solution for disabling a Node's drag listener?

@kathy-phet and I think this is likely to come up in other sims like Bending Light. A client may want to fix the position of the LaserNode, but leave the button on it interactive. We're going to mark this issue for further discussion at PhET-iO meeting.

[pixelzoom]

I've moved the general discussion about how to disable listeners to phetsims/scenery#1041.

[pixelzoom]

I've moved the general discussion about how to disable listeners to https://github.com/phetsims/ph-scale/issues/133.

So our remaining decisions here are:

(1) Whether the dropper should be draggable. If not, then (2) is moot.

(2) Whether what we come up with in phetsims/scenery#1041 should be applied here to allow the client to disable dragging of the dropper.

[pixelzoom]

3/5/20 design meeting:

• keep the dropper movable
• we don't want to change the tandem hierarchy for dropperNode
• address disabling input listeners in how to disable input listeners scenery#1041

Closing.