Use PhetioGroup instead of ObservableArray of photons, see phetsims/molecules-and-light#353

Author: samreid

js/moleculesandlight/view/MoleculesAndLightScreenView.js

@@ -257,7 +257,7 @@ class MoleculesAndLightScreenView extends ScreenView {
     ) );
 
     // add the sound generator that will produce the sounds when photons are emitted by the lamps or the active molecule
-    soundManager.addSoundGenerator( new PhotonEmissionSoundGenerator( photonAbsorptionModel.photons ) );
+    soundManager.addSoundGenerator( new PhotonEmissionSoundGenerator( photonAbsorptionModel.photonGroup ) );
 
     // We may want to disable the PlayPauseButton when the light source is off, but we aren't sure yet. This will let
     // us test behavior and make sure it doesn't have other UX impacts

js/moleculesandlight/view/ObservationWindow.js

@@ -171,7 +171,7 @@ function ObservationWindow( photonAbsorptionModel, modelViewTransform, tandem )
   photonAbsorptionModel.activeMolecules.addItemAddedListener( addMoleculeToWindow );
 
   // Set up the event listeners for adding and removing photons.
-  photonAbsorptionModel.photons.addItemAddedListener( function( addedPhoton ) {
+  photonAbsorptionModel.photonGroup.elementCreatedEmitter.addListener( function( addedPhoton ) {
     const photonNode = new PhotonNode( addedPhoton, self.modelViewTransform );
     photonLayer.addChild( photonNode );
 
@@ -181,11 +181,11 @@ function ObservationWindow( photonAbsorptionModel, modelViewTransform, tandem )
     };
     addedPhoton.positionProperty.link( photonPositionObserver );
 
-    photonAbsorptionModel.photons.addItemRemovedListener( function removalListener( removedPhoton ) {
+    photonAbsorptionModel.photonGroup.elementDisposedEmitter.addListener( function removalListener( removedPhoton ) {
       if ( removedPhoton === addedPhoton ) {
         addedPhoton.positionProperty.hasListener( photonPositionObserver ) && addedPhoton.positionProperty.unlink( photonPositionObserver );
         photonLayer.removeChild( photonNode );
-        photonAbsorptionModel.photons.removeItemRemovedListener( removalListener );
+        photonAbsorptionModel.photonGroup.elementDisposedEmitter.removeListener( removalListener );
       }
     } );
   } );
@@ -282,18 +282,11 @@ inherit( Rectangle, ObservationWindow, {
    */
   photonCheckBounds: function() {
 
-    const photonsToRemove = [];
-    for ( let photon = 0; photon < this.photonAbsorptionModel.photons.length; photon++ ) {
-      if ( !this.particleRemovalBounds.containsPoint( this.modelViewTransform.modelToViewPosition( this.photonAbsorptionModel.photons.get( photon ).positionProperty.get() ) ) ) {
-        photonsToRemove.push( this.photonAbsorptionModel.photons.get( photon ) );
-      }
-    }
-    this.photonAbsorptionModel.photons.removeAll( photonsToRemove );
-
-    // dispose all photons that leave the observation window
-    for ( let i = 0; i < photonsToRemove.length; i++ ) {
-      this.photonAbsorptionModel.photonGroup.disposeElement( photonsToRemove[ i ] );
-    }
+    const photonsToRemove = this.photonAbsorptionModel.photonGroup.filter( photon => {
+      const position = this.modelViewTransform.modelToViewPosition( photon.positionProperty.get() );
+      return !this.particleRemovalBounds.containsPoint( position );
+    } );
+    photonsToRemove.forEach( photon => this.photonAbsorptionModel.photonGroup.disposeElement( photon ) );
   },
 
   /**

js/moleculesandlight/view/ObservationWindowAlertManager.js

@@ -205,7 +205,7 @@ class ObservationWindowAlertManager {
     let alert = null;
 
     const emitterOn = model.photonEmitterOnProperty.get();
-    const hasPhotons = model.photons.length > 0;
+    const hasPhotons = model.photonGroup.count > 0;
     const targetMolecule = model.targetMolecule;
 
     if ( targetMolecule ) {

js/moleculesandlight/view/PhotonEmissionSoundGenerator.js

@@ -38,10 +38,10 @@ const PLAY_MOLECULE_EMISSION_X_POSITION = 0;
 class PhotonEmissionSoundGenerator extends SoundGenerator {
 
   /**
-   * @param {ObservableArrayDef<Photon>} photons
+   * @param {PhetioGroup} photonGroup
    * @param {Object} [options]
    */
-  constructor( photons, options ) {
+  constructor( photonGroup, options ) {
 
     options = merge( {}, options );
     super( options );
@@ -96,7 +96,7 @@ class PhotonEmissionSoundGenerator extends SoundGenerator {
     } );
 
     // listen for new photons and play sounds or set them up to be played later when appropriate
-    photons.addItemAddedListener( photon => {
+    photonGroup.elementCreatedEmitter.addListener( photon => {
       const photonXPosition = photon.positionProperty.value.x;
 
       if ( photonXPosition === PLAY_MOLECULE_EMISSION_X_POSITION ) {