add list item that describes IR layers, see #374

js/layer-model/view/LayerModelObservationWindowPDOMNode.ts

@@ -3,6 +3,9 @@
 import ObservationWindowPDOMNode from '../../common/view/ObservationWindowPDOMNode.js';
 import greenhouseEffect from '../../greenhouseEffect.js';
 import LayerModelModel from '../model/LayerModelModel.js';
+import { Node } from '../../../../scenery/js/imports.js';
+import InfraredAbsorbingLayersDescriptionProperty from './describers/InfraredAbsorbingLayersDescriptionProperty.js';
+import StringUtils from '../../../../phetcommon/js/util/StringUtils.js';
 
 /**
  * Responsible for PDOM content related to the observation window used in the waves screen.
@@ -14,6 +17,20 @@ class LayerModelObservationWindowPDOMNode extends ObservationWindowPDOMNode {
 
   public constructor( model: LayerModelModel ) {
     super( model.sunEnergySource.isShiningProperty );
+
+    // Create a string Property that describes the number of infrared-absorbing layers in the atmosphere.
+    const infraredAbsorbingLayersPhraseProperty = new InfraredAbsorbingLayersDescriptionProperty(
+      model.numberOfActiveAtmosphereLayersProperty
+    );
+
+    // Create the node that will place the description of IR layers into the PDOM.
+    const irLayersItemNode = new Node( { tagName: 'li' } );
+    this.addChild( irLayersItemNode );
+
+    // Update the PDOM item when the description string changes.
+    infraredAbsorbingLayersPhraseProperty.link( infraredAbsorbingLayersPhrase => {
+      irLayersItemNode.innerContent = StringUtils.capitalize( infraredAbsorbingLayersPhrase ) + '.';
+    } );
   }
 }
 

js/layer-model/view/LayerModelScreenSummaryContentNode.ts

@@ -13,6 +13,7 @@ import GreenhouseEffectScreenSummaryContentNode from '../../common/view/Greenhou
 import DerivedProperty from '../../../../axon/js/DerivedProperty.js';
 import StringUtils from '../../../../phetcommon/js/util/StringUtils.js';
 import TemperatureDescriber from '../../common/view/describers/TemperatureDescriber.js';
+import InfraredAbsorbingLayersDescriptionProperty from './describers/InfraredAbsorbingLayersDescriptionProperty.js';
 
 export default class LayerModelScreenSummaryContentNode extends GreenhouseEffectScreenSummaryContentNode {
 
@@ -25,28 +26,9 @@ export default class LayerModelScreenSummaryContentNode extends GreenhouseEffect
       GreenhouseEffectStrings.a11y.layerModel.screenSummary.controlAreaDescriptionStringProperty
     );
 
-    // A derived Property containing a string that represents the number of infrared-absorbing layers in the atmosphere,
-    // for example, "one infrared absorbing layer in atmosphere".
-    const infraredAbsorbingLayersPhraseProperty = new DerivedProperty(
-      [ model.numberOfActiveAtmosphereLayersProperty ],
-      numberOfActiveAtmosphereLayers => {
-
-        // parameter checking
-        assert && assert(
-          numberOfActiveAtmosphereLayers >= 0,
-          `numberOfActiveAtmosphereLayers must be positive, got ${numberOfActiveAtmosphereLayers}`
-        );
-
-        return StringUtils.fillIn(
-          GreenhouseEffectStrings.a11y.layerModel.observationWindow.numberOfAbsorbingLayersPatternStringProperty,
-          {
-            number: numberOfActiveAtmosphereLayers > 0 ?
-                    numberOfActiveAtmosphereLayers :
-                    GreenhouseEffectStrings.a11y.qualitativeAmountDescriptions.noStringProperty, // say 'no' for zero
-            s: numberOfActiveAtmosphereLayers === 1 ? '' : 's' // use plural except for a single layer
-          }
-        );
-      }
+    // a string Property that describes the number of infrared-absorbing layers in the atmosphere
+    const infraredAbsorbingLayersPhraseProperty = new InfraredAbsorbingLayersDescriptionProperty(
+      model.numberOfActiveAtmosphereLayersProperty
     );
 
     // A derived property containing a string that describes the surface temperature, for example, "Earth's surface

js/layer-model/view/describers/InfraredAbsorbingLayersDescriptionProperty.ts

@@ -0,0 +1,44 @@
+// Copyright 2023, University of Colorado Boulder
+
+/**
+ * InfraredAbsorbingLayersDescriptionProperty is a Property<string> that describes the current number of the IR-
+ * absorbing layers in the atmosphere.  For example, one possible value is "2 infrared absorbing layers in atmosphere".
+ *
+ * @author John Blanco (PhET Interactive Simulations)
+ */
+import greenhouseEffect from '../../../greenhouseEffect.js';
+import StringProperty from '../../../../../axon/js/StringProperty.js';
+import Multilink from '../../../../../axon/js/Multilink.js';
+import TRangedProperty from '../../../../../axon/js/TRangedProperty.js';
+import GreenhouseEffectStrings from '../../../GreenhouseEffectStrings.js';
+import StringUtils from '../../../../../phetcommon/js/util/StringUtils.js';
+
+class InfraredAbsorbingLayersDescriptionProperty extends StringProperty {
+  public constructor( numberOfActiveAtmosphereLayersProperty: TRangedProperty ) {
+    super( '' );
+
+    // Monitor the intensity Property and update the value of the string.
+    Multilink.multilink( [ numberOfActiveAtmosphereLayersProperty ], numberOfActiveAtmosphereLayers => {
+
+        // parameter checking
+        assert && assert(
+          numberOfActiveAtmosphereLayers >= 0,
+          `numberOfActiveAtmosphereLayers must be positive, got ${numberOfActiveAtmosphereLayers}`
+        );
+
+        this.value = StringUtils.fillIn(
+          GreenhouseEffectStrings.a11y.layerModel.observationWindow.numberOfAbsorbingLayersPatternStringProperty,
+          {
+            number: numberOfActiveAtmosphereLayers > 0 ?
+                    numberOfActiveAtmosphereLayers :
+                    GreenhouseEffectStrings.a11y.qualitativeAmountDescriptions.noStringProperty, // say 'no' for zero
+            s: numberOfActiveAtmosphereLayers === 1 ? '' : 's' // use plural except for a single layer
+          }
+        );
+      }
+    );
+  }
+}
+
+greenhouseEffect.register( 'InfraredAbsorbingLayersDescriptionProperty', InfraredAbsorbingLayersDescriptionProperty );
+export default InfraredAbsorbingLayersDescriptionProperty;

js/waves/view/WaveLandscapeObservationWindowPDOMNode.ts

@@ -39,7 +39,7 @@ class WaveLandscapeObservationWindowPDOMNode extends LandscapeObservationWindowP
             EnergyRepresentation.WAVE
           );
 
-          // if the sun isn't shining yet, hide this portion of the content
+          // If the sun isn't shining yet, hide this portion of the content.
           this.sunlightItemNode.pdomVisible = isShining;
         }
       );