Don't reset threashold when resetting color mode (#932)

* don't reset threshold when changing modes

* updated docs

docs/tutorials/city-shaper.md

@@ -32,6 +32,10 @@
     "name": "Moving with Gyro",
     "description": "Use the gyro for correct the robot trajectory.",
     "youTubeId": "ufiOPvW37xc"
+}, {
+    "name": "Line following with 1 color sensor",
+    "description": "Simple line following using the color sensor.",
+    "youTubeId": "_LeduyKQVjg"
 }]
 ```
 

libs/color-sensor/color.ts

@@ -73,13 +73,7 @@ namespace sensors {
         }
 
         setMode(m: ColorSensorMode) {
-            if (m == ColorSensorMode.AmbientLightIntensity) {
-                this.thresholdDetector.setLowThreshold(5);
-                this.thresholdDetector.setHighThreshold(20);
-            } else {
-                this.thresholdDetector.setLowThreshold(20);
-                this.thresholdDetector.setHighThreshold(80);
-            }
+            // don't change threshold after initialization
             this._setMode(m)
         }
 

libs/core/input.ts

@@ -814,10 +814,10 @@ namespace sensors {
 
     export class ThresholdDetector {
         public id: number;
-        public min: number;
-        public max: number;
-        public lowThreshold: number;
-        public highThreshold: number;
+        private min: number;
+        private max: number;
+        private lowThreshold: number;
+        private highThreshold: number;
         public level: number;
         public state: ThresholdState;