Handling visibility in listed mixins, see phetsims/chipper#1267

js/layout/HeightSizable.ts

@@ -71,9 +71,8 @@ const HeightSizable = memoize( <SuperType extends Constructor>( type: SuperType
     public readonly isHeightResizableProperty: TinyProperty<boolean> = new TinyProperty<boolean>( true );
 
     // Flags so that we can change one (parent/local) value and not enter an infinite loop changing the other
-    // (scenery-internal) - would be private, but can't be with mixin constraints
-    public _preferredHeightChanging = false;
-    public _minimumHeightChanging = false;
+    private _preferredHeightChanging = false;
+    private _minimumHeightChanging = false;
 
     // IMPORTANT: If you're mixing this in, typically don't pass options that HeightSizable would take through the
     // constructor. It will hit Node's mutate() likely, and then will fail because we haven't been able to set the

js/layout/WidthSizable.ts

@@ -71,9 +71,8 @@ const WidthSizable = memoize( <SuperType extends Constructor>( type: SuperType )
     public readonly isWidthResizableProperty: TinyProperty<boolean> = new TinyProperty<boolean>( true );
 
     // Flags so that we can change one (parent/local) value and not enter an infinite loop changing the other
-    // (scenery-internal) - would be private, but can't be with mixin constraints
-    public _preferredWidthChanging = false;
-    public _minimumWidthChanging = false;
+    private _preferredWidthChanging = false;
+    private _minimumWidthChanging = false;
 
     // IMPORTANT: If you're mixing this in, typically don't pass options that WidthSizable would take through the
     // constructor. It will hit Node's mutate() likely, and then will fail because we haven't been able to set the

js/layout/constraints/FlowConfigurable.ts

@@ -88,12 +88,11 @@ export type FlowConfigurableOptions = {
 export type ExternalFlowConfigurableOptions = WithoutNull<FlowConfigurableOptions, Exclude<keyof FlowConfigurableOptions, 'minContentWidth' | 'minContentHeight' | 'maxContentWidth' | 'maxContentHeight'>>;
 
 const FlowConfigurable = memoize( <SuperType extends Constructor>( type: SuperType ) => {
-  return class extends type {
+  return class FlowConfirableMixin extends type {
 
-    // (scenery-internal) - considered private, but TypeScript mixins won't support private
-    public _orientation: Orientation = Orientation.HORIZONTAL;
+    protected _orientation: Orientation = Orientation.HORIZONTAL;
 
-    // (scenery-internal) - considered private, but TypeScript mixins won't support private
+    // (scenery-internal)
     public _align: LayoutAlign | null = null;
     public _stretch: boolean | null = null;
     public _leftMargin: number | null = null;

js/layout/constraints/GridConfigurable.ts

@@ -83,9 +83,9 @@ export type GridConfigurableOptions = {
 export type ExternalGridConfigurableOptions = WithoutNull<GridConfigurableOptions, Exclude<keyof GridConfigurableOptions, 'minContentWidth' | 'minContentHeight' | 'maxContentWidth' | 'maxContentHeight'>>;
 
 const GridConfigurable = memoize( <SuperType extends Constructor>( type: SuperType ) => {
-  return class extends type {
+  return class GridConfigurableMixin extends type {
 
-    // (scenery-internal) - considered private, but TypeScript mixins won't support private
+    // (scenery-internal)
     public _xAlign: LayoutAlign | null = null;
     public _yAlign: LayoutAlign | null = null;
     public _xStretch: boolean | null = null;