Add existing to tracked

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

@@ -0,0 +1,64 @@
+import { defined, DeveloperError, Event } from "@cesium/engine";
+import knockout from "./ThirdParty/knockout.js";
+
+/**
+ * Create a Command from a given function, for use with ViewModels.
+ *
+ * A Command is a function with an extra <code>canExecute</code> observable property to determine
+ * whether the command can be executed.  When executed, a Command function will check the
+ * value of <code>canExecute</code> and throw if false.  It also provides events for when
+ * a command has been or is about to be executed.
+ *
+ * @function
+ *
+ * @param {Function} func The function to execute.
+ * @param {boolean} [canExecute=true] A boolean indicating whether the function can currently be executed.
+ */
+function createCommand(func, canExecute) {
+  //>>includeStart('debug', pragmas.debug);
+  if (!defined(func)) {
+    throw new DeveloperError("func is required.");
+  }
+  //>>includeEnd('debug');
+
+  canExecute = canExecute ?? true;
+
+  const beforeExecute = new Event();
+  const afterExecute = new Event();
+
+  function command() {
+    //>>includeStart('debug', pragmas.debug);
+    if (!command.canExecute) {
+      throw new DeveloperError("Cannot execute command, canExecute is false.");
+    }
+    //>>includeEnd('debug');
+
+    const commandInfo = {
+      args: arguments,
+      cancel: false,
+    };
+
+    let result;
+    beforeExecute.raiseEvent(commandInfo);
+    if (!commandInfo.cancel) {
+      result = func.apply(null, arguments);
+      afterExecute.raiseEvent(result);
+    }
+    return result;
+  }
+
+  command.canExecute = canExecute;
+  knockout.track(command, ["canExecute"]);
+
+  Object.defineProperties(command, {
+    beforeExecute: {
+      value: beforeExecute,
+    },
+    afterExecute: {
+      value: afterExecute,
+    },
+  });
+
+  return command;
+}
+export default createCommand;