Add existing to tracked

node_modules/@cesium/engine/Source/DataSources/CallbackProperty.js

@@ -0,0 +1,117 @@
+import defined from "../Core/defined.js";
+import DeveloperError from "../Core/DeveloperError.js";
+import Event from "../Core/Event.js";
+import JulianDate from "../Core/JulianDate.js";
+
+/**
+ * A {@link Property} whose value is lazily evaluated by a callback function.
+ *
+ * @alias CallbackProperty
+ * @constructor
+ *
+ * @param {CallbackProperty.Callback} callback The function to be called when the property is evaluated.
+ * @param {boolean} isConstant <code>true</code> when the callback function returns the same value every time, <code>false</code> if the value will change.
+ */
+function CallbackProperty(callback, isConstant) {
+  this._callback = undefined;
+  this._isConstant = undefined;
+  this._definitionChanged = new Event();
+  this.setCallback(callback, isConstant);
+}
+
+Object.defineProperties(CallbackProperty.prototype, {
+  /**
+   * Gets a value indicating if this property is constant.
+   * @memberof CallbackProperty.prototype
+   *
+   * @type {boolean}
+   * @readonly
+   */
+  isConstant: {
+    get: function () {
+      return this._isConstant;
+    },
+  },
+  /**
+   * Gets the event that is raised whenever the definition of this property changes.
+   * The definition is changed whenever setCallback is called.
+   * @memberof CallbackProperty.prototype
+   *
+   * @type {Event}
+   * @readonly
+   */
+  definitionChanged: {
+    get: function () {
+      return this._definitionChanged;
+    },
+  },
+});
+
+const timeScratch = new JulianDate();
+
+/**
+ * Gets the value of the property.
+ *
+ * @param {JulianDate} [time=JulianDate.now()] The time for which to retrieve the value. If omitted, the current system time is used.
+ * @param {object} [result] The object to store the value into, if omitted, a new instance is created and returned.
+ * @returns {object} The modified result parameter or a new instance if the result parameter was not supplied or is unsupported.
+ */
+CallbackProperty.prototype.getValue = function (time, result) {
+  if (!defined(time)) {
+    time = JulianDate.now(timeScratch);
+  }
+  return this._callback(time, result);
+};
+
+/**
+ * Sets the callback to be used.
+ *
+ * @param {CallbackProperty.Callback} callback The function to be called when the property is evaluated.
+ * @param {boolean} isConstant <code>true</code> when the callback function returns the same value every time, <code>false</code> if the value will change.
+ */
+CallbackProperty.prototype.setCallback = function (callback, isConstant) {
+  //>>includeStart('debug', pragmas.debug);
+  if (!defined(callback)) {
+    throw new DeveloperError("callback is required.");
+  }
+  if (!defined(isConstant)) {
+    throw new DeveloperError("isConstant is required.");
+  }
+  //>>includeEnd('debug');
+
+  const changed =
+    this._callback !== callback || this._isConstant !== isConstant;
+
+  this._callback = callback;
+  this._isConstant = isConstant;
+
+  if (changed) {
+    this._definitionChanged.raiseEvent(this);
+  }
+};
+
+/**
+ * Compares this property to the provided property and returns
+ * <code>true</code> if they are equal, <code>false</code> otherwise.
+ *
+ * @param {Property} [other] The other property.
+ * @returns {boolean} <code>true</code> if left and right are equal, <code>false</code> otherwise.
+ */
+CallbackProperty.prototype.equals = function (other) {
+  return (
+    this === other ||
+    (other instanceof CallbackProperty &&
+      this._callback === other._callback &&
+      this._isConstant === other._isConstant)
+  );
+};
+
+/**
+ * A function that returns the value of the property.
+ * @callback CallbackProperty.Callback
+ *
+ * @param {JulianDate} [time=JulianDate.now()] The time for which to retrieve the value. If omitted, the current system time is used.
+ * @param {object} [result] The object to store the value into. If omitted, the function must create and return a new instance.
+ * @returns {object} The modified result parameter, or a new instance if the result parameter was not supplied or is unsupported.
+ */
+export default CallbackProperty;