From 3d0f5454862121d1bf175db091f29c58178817b4 Mon Sep 17 00:00:00 2001
From: jbphet <jpblanco@yahoo.com>
Date: Thu, 9 Jan 2025 16:48:21 -0700
Subject: [PATCH] clear counts when measurement time changes, see
 https://github.com/phetsims/quantum-measurement/issues/54

---
 js/bloch-sphere/model/BlochSphereModel.ts       | 12 ++++++++++--
 js/bloch-sphere/view/MeasurementTimerControl.ts |  2 ++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/js/bloch-sphere/model/BlochSphereModel.ts b/js/bloch-sphere/model/BlochSphereModel.ts
index 256070c..0da9c09 100644
--- a/js/bloch-sphere/model/BlochSphereModel.ts
+++ b/js/bloch-sphere/model/BlochSphereModel.ts
@@ -169,6 +169,11 @@ class BlochSphereModel implements TModel {
       tandem: providedOptions.tandem.createTandem( 'measurementStateProperty' )
     } );
 
+    // Clear the measurement counts when the time to measurement changes, since this changes the nature of the
+    // measurement that is being made.
+    this.timeToMeasurementProperty.link( () => this.resetCounts() );
+
+    // Change the selected preset state direction to CUSTOM when the user manually changes the angles of the Bloch Sphere.
     Multilink.multilink(
       [
         this.preparationBlochSphere.polarAngleProperty,
@@ -331,8 +336,11 @@ class BlochSphereModel implements TModel {
     } );
 
     if ( this.measurementStateProperty.value === 'timingObservation' ) {
-      this.measurementTimeProperty.value = this.measurementTimeProperty.value + dt;
-      if ( this.measurementTimeProperty.value > this.timeToMeasurementProperty.value ) {
+      this.measurementTimeProperty.value = Math.min(
+        this.measurementTimeProperty.value + dt,
+        this.timeToMeasurementProperty.value
+      );
+      if ( this.measurementTimeProperty.value >= this.timeToMeasurementProperty.value ) {
 
         // The time when the observation should be made has been reached.  Make the observation.
         this.observe();
diff --git a/js/bloch-sphere/view/MeasurementTimerControl.ts b/js/bloch-sphere/view/MeasurementTimerControl.ts
index fb439e4..a2a09b4 100644
--- a/js/bloch-sphere/view/MeasurementTimerControl.ts
+++ b/js/bloch-sphere/view/MeasurementTimerControl.ts
@@ -62,6 +62,8 @@ export default class MeasurementTimerControl extends Node {
       majorTickLength: 10,
       minorTickLength: 5
     } );
+
+    // Add the major and minor tick marks to the slider.
     timeToMeasurementSlider.addMajorTick( 0, new Text( '0', { font: new PhetFont( 15 ) } ) );
     timeToMeasurementSlider.addMajorTick( maxMeasurementTime, new Text( 't', { font: new PhetFont( 15 ) } ) );
     _.times( NUMBER_OF_MINOR_TICKS, i => {