incorrect behavior during `?shuffleListeners`

[samreid]

Discovered in https://github.com/phetsims/axon/issues/215 and https://github.com/phetsims/quadrilateral/issues/398, the sim has some incorrect behavior during ?shuffleListeners.

[samreid]

I also saw this one time while dragging:

[jessegreenberg]

Thanks! I am seeing problems like this in master at the moment too without ?shuffleListeners, we may have a regression from recent commits.

[jessegreenberg]

Checking out recent SHAs, I start seeing bad behavior at 3696fa6a0b71858db56642b4d32f2e25f7002ea0, Ill take a look.

[jessegreenberg]

Fixed in the above commit, sim is fuzzing without error again. But there are still some problems with ?shuffleListeners. No errors but the shape looks wrong.

[jessegreenberg]

Here are the vertex positions:

For a view that looks like this:

So perhaps it is just a view problem. In this state if I only check one of the visibility checkboxes, the view corrects itself.

nly check one of the visibility checkboxes, the view corrects itself.

Nope, that is just the markersVisibleProperty because the multilink for re-drawing sides has this:

Multilink.multilink( [ side.vertex1.positionProperty, side.vertex2.positionProperty, markersVisibleProperty ], ( vertex1Position, vertex2Position, markersVisible ) => {

The multilink has the right Vertex position values, but it uses a QuadrilateralSide.modelLine to create the shape. So here is the problematic order of events.

• vertex PositionProperties change
• The MultiLink in QuadrilateralSideNode fires to redraw the side
• updateOrderDependentProperties is called which updates the model shape

This would be fixed if the QuadrilateralSide.modelLine was observable, so that the view can update after the modelLine is set. Or, QuadrilateralSide.modelLine could be removed and we could just use the vertex positions.

[jessegreenberg]

Alright, fixed in the above commit. I made the side model Line Shape observable so we can link to it and guarantee that it will be up to date after vertex positions have been set.

Playing with the sim, I don't see any more odd behavior and no errors when fuzzing with ?shuffleListeners. Closing.