Add existing to tracked

node_modules/@cesium/widgets/Source/ToggleButtonViewModel.js

@@ -0,0 +1,54 @@
+import { Frozen, defined, DeveloperError } from "@cesium/engine";
+import knockout from "./ThirdParty/knockout.js";
+
+/**
+ * A view model which exposes the properties of a toggle button.
+ * @alias ToggleButtonViewModel
+ * @constructor
+ *
+ * @param {Command} command The command which will be executed when the button is toggled.
+ * @param {object} [options] Object with the following properties:
+ * @param {boolean} [options.toggled=false] A boolean indicating whether the button should be initially toggled.
+ * @param {string} [options.tooltip=''] A string containing the button's tooltip.
+ */
+function ToggleButtonViewModel(command, options) {
+  //>>includeStart('debug', pragmas.debug);
+  if (!defined(command)) {
+    throw new DeveloperError("command is required.");
+  }
+  //>>includeEnd('debug');
+
+  this._command = command;
+
+  options = options ?? Frozen.EMPTY_OBJECT;
+
+  /**
+   * Gets or sets whether the button is currently toggled.  This property is observable.
+   * @type {boolean}
+   * @default false
+   */
+  this.toggled = options.toggled ?? false;
+
+  /**
+   * Gets or sets the button's tooltip.  This property is observable.
+   * @type {string}
+   * @default ''
+   */
+  this.tooltip = options.tooltip ?? "";
+
+  knockout.track(this, ["toggled", "tooltip"]);
+}
+
+Object.defineProperties(ToggleButtonViewModel.prototype, {
+  /**
+   * Gets the command which will be executed when the button is toggled.
+   * @memberof ToggleButtonViewModel.prototype
+   * @type {Command}
+   */
+  command: {
+    get: function () {
+      return this._command;
+    },
+  },
+});
+export default ToggleButtonViewModel;