Independent time conductor (#3988)

* Independent time API implementation
* Independent time conductor in plan view

Co-authored-by: charlesh88 <charles.f.hacskaylo@nasa.gov>
Co-authored-by: Jamie V <jamie.j.vigliotta@nasa.gov>
Co-authored-by: Andrew Henry <akhenry@gmail.com>

src/api/time/IndependentTimeContext.js

@@ -0,0 +1,94 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2021, United States Government
+ * as represented by the Administrator of the National Aeronautics and Space
+ * Administration. All rights reserved.
+ *
+ * Open MCT is licensed under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ * Open MCT includes source code licensed under additional open source
+ * licenses. See the Open Source Licenses file (LICENSES.md) included with
+ * this source code distribution or the Licensing information page available
+ * at runtime from the About dialog for additional information.
+ *****************************************************************************/
+
+import TimeContext from "./TimeContext";
+
+/**
+ * The IndependentTimeContext handles getting and setting time of the openmct application in general.
+ * Views will use the GlobalTimeContext unless they specify an alternate/independent time context here.
+ */
+class IndependentTimeContext extends TimeContext {
+    constructor(globalTimeContext, key) {
+        super();
+        this.key = key;
+
+        this.globalTimeContext = globalTimeContext;
+    }
+
+    /**
+     * Set the active clock. Tick source will be immediately subscribed to
+     * and ticking will begin. Offsets from 'now' must also be provided. A clock
+     * can be unset by calling {@link stopClock}.
+     *
+     * @param {Clock || string} keyOrClock The clock to activate, or its key
+     * @param {ClockOffsets} offsets on each tick these will be used to calculate
+     * the start and end bounds. This maintains a sliding time window of a fixed
+     * width that automatically updates.
+     * @fires module:openmct.TimeAPI~clock
+     * @return {Clock} the currently active clock;
+     */
+    clock(keyOrClock, offsets) {
+        if (arguments.length === 2) {
+            let clock;
+
+            if (typeof keyOrClock === 'string') {
+                clock = this.globalTimeContext.clocks.get(keyOrClock);
+                if (clock === undefined) {
+                    throw "Unknown clock '" + keyOrClock + "'. Has it been registered with 'addClock'?";
+                }
+            } else if (typeof keyOrClock === 'object') {
+                clock = keyOrClock;
+                if (!this.globalTimeContext.clocks.has(clock.key)) {
+                    throw "Unknown clock '" + keyOrClock.key + "'. Has it been registered with 'addClock'?";
+                }
+            }
+
+            const previousClock = this.activeClock;
+            if (previousClock !== undefined) {
+                previousClock.off("tick", this.tick);
+            }
+
+            this.activeClock = clock;
+
+            /**
+             * The active clock has changed. Clock can be unset by calling {@link stopClock}
+             * @event clock
+             * @memberof module:openmct.TimeAPI~
+             * @property {Clock} clock The newly activated clock, or undefined
+             * if the system is no longer following a clock source
+             */
+            this.emit("clock", this.activeClock);
+
+            if (this.activeClock !== undefined) {
+                this.clockOffsets(offsets);
+                this.activeClock.on("tick", this.tick);
+            }
+
+        } else if (arguments.length === 1) {
+            throw "When setting the clock, clock offsets must also be provided";
+        }
+
+        return this.activeClock;
+    }
+}
+
+export default IndependentTimeContext;