feat(ElementItem): optionally hide grippy

* Allow displaying and updating multiple y axes

* Fix label updates when series are added or removed

* Add tests for y axes configuration in the inspector

* Addresses review comments: Renames properties for clarity and reorganize code for readability.

* test: fix selector for snapshot test

* Fix e2e selectors

Co-authored-by: Khalid Adil <khalidadil29@gmail.com>
Co-authored-by: Jesse Mazzella <jesse.d.mazzella@nasa.gov>
Co-authored-by: Jesse Mazzella <ozyx@users.noreply.github.com>

e2e/tests/functional/plugins/plot/autoscale.e2e.spec.js

@@ -156,7 +156,7 @@ async function turnOffAutoscale(page) {
     await page.locator('text=Unnamed Overlay Plot Snapshot >> button').nth(3).click();
 
     // uncheck autoscale
-    await page.locator('text=Y Axis Label Log mode Auto scale Padding >> input[type="checkbox"] >> nth=1').uncheck();
+    await page.getByRole('listitem').filter({ hasText: 'Auto scale' }).getByRole('checkbox').uncheck();
 
     // save
     await page.locator('text=Snapshot Save and Finish Editing Save and Continue Editing >> button').nth(1).click();

e2e/tests/functional/plugins/plot/logPlot.e2e.spec.js

@@ -205,7 +205,8 @@ async function enableEditMode(page) {
  */
 async function enableLogMode(page) {
     // turn on log mode
-    await page.locator('text=Y Axis Label Log mode Auto scale Padding >> input[type="checkbox"]').first().check();
+    await page.getByRole('listitem').filter({ hasText: 'Log mode' }).getByRole('checkbox').check();
+    // await page.locator('text=Y Axis Label Log mode Auto scale Padding >> input[type="checkbox"]').first().check();
 }
 
 /**
@@ -213,7 +214,7 @@ async function enableLogMode(page) {
  */
 async function disableLogMode(page) {
     // turn off log mode
-    await page.locator('text=Y Axis Label Log mode Auto scale Padding >> input[type="checkbox"]').first().uncheck();
+    await page.getByRole('listitem').filter({ hasText: 'Log mode' }).getByRole('checkbox').uncheck();
 }
 
 /**

e2e/tests/functional/plugins/plot/overlayPlot.e2e.spec.js

@@ -0,0 +1,116 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2022, 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.
+ *****************************************************************************/
+
+/*
+Tests to verify log plot functionality. Note this test suite if very much under active development and should not
+necessarily be used for reference when writing new tests in this area.
+*/
+
+const { test, expect } = require('../../../../pluginFixtures');
+const { createDomainObjectWithDefaults } = require('../../../../appActions');
+
+test.describe('Overlay Plot', () => {
+    test('Plot legend color is in sync with plot series color', async ({ page }) => {
+        await page.goto('/', { waitUntil: 'networkidle' });
+        const overlayPlot = await createDomainObjectWithDefaults(page, {
+            type: "Overlay Plot"
+        });
+
+        await createDomainObjectWithDefaults(page, {
+            type: "Sine Wave Generator",
+            parent: overlayPlot.uuid
+        });
+
+        await page.goto(overlayPlot.url);
+
+        // navigate to plot series color palette
+        await page.click('.l-browse-bar__actions__edit');
+        await page.locator('li.c-tree__item.menus-to-left .c-disclosure-triangle').click();
+        await page.locator('.c-click-swatch--menu').click();
+        await page.locator('.c-palette__item[style="background: rgb(255, 166, 61);"]').click();
+
+        // gets color for swatch located in legend
+        const element = await page.waitForSelector('.plot-series-color-swatch');
+        const color = await element.evaluate((el) => {
+            return window.getComputedStyle(el).getPropertyValue('background-color');
+        });
+
+        expect(color).toBe('rgb(255, 166, 61)');
+    });
+    test('The elements pool supports dragging series into multiple y-axis buckets', async ({ page }) => {
+        await page.goto('/', { waitUntil: 'networkidle' });
+        const overlayPlot = await createDomainObjectWithDefaults(page, {
+            type: "Overlay Plot"
+        });
+
+        await createDomainObjectWithDefaults(page, {
+            type: "Sine Wave Generator",
+            name: 'swg a',
+            parent: overlayPlot.uuid
+        });
+        await createDomainObjectWithDefaults(page, {
+            type: "Sine Wave Generator",
+            name: 'swg b',
+            parent: overlayPlot.uuid
+        });
+        await createDomainObjectWithDefaults(page, {
+            type: "Sine Wave Generator",
+            name: 'swg c',
+            parent: overlayPlot.uuid
+        });
+        await createDomainObjectWithDefaults(page, {
+            type: "Sine Wave Generator",
+            name: 'swg d',
+            parent: overlayPlot.uuid
+        });
+        await createDomainObjectWithDefaults(page, {
+            type: "Sine Wave Generator",
+            name: 'swg e',
+            parent: overlayPlot.uuid
+        });
+
+        await page.goto(overlayPlot.url);
+        await page.click('button[title="Edit"]');
+
+        // Expand the elements pool vertically
+        await page.locator('.l-pane__handle').nth(2).hover({ trial: true });
+        await page.mouse.down();
+        await page.mouse.move(0, 100);
+        await page.mouse.up();
+
+        await page.locator('#inspector-elements-tree >> text=swg a').dragTo(page.locator('[aria-label="Element Item Group"]').nth(1));
+        await page.locator('#inspector-elements-tree >> text=swg c').dragTo(page.locator('[aria-label="Element Item Group"]').nth(1));
+        await page.locator('#inspector-elements-tree >> text=swg e').dragTo(page.locator('[aria-label="Element Item Group"]').nth(1));
+        await page.locator('#inspector-elements-tree >> text=swg b').dragTo(page.locator('[aria-label="Element Item Group"]').nth(2));
+        const elementsTree = await page.locator('#inspector-elements-tree').allInnerTexts();
+        expect(elementsTree.join('').split('\n')).toEqual([
+            "Y Axis 1",
+            "swg d",
+            "Y Axis 2",
+            "swg e",
+            "swg c",
+            "swg a",
+            "Y Axis 3",
+            "swg b"
+        ]);
+    });
+});

src/plugins/plot/MctPlot.vue

@@ -34,23 +34,26 @@
         @legendHoverChanged="legendHoverChanged"
     />
     <div class="plot-wrapper-axis-and-display-area flex-elem grows">
-        <y-axis
-            v-if="seriesModels.length > 0"
-            :tick-width="tickWidth"
-            :single-series="seriesModels.length === 1"
-            :has-same-range-value="hasSameRangeValue"
-            :series-model="seriesModels[0]"
-            :style="{
-                left: (plotWidth - tickWidth) + 'px'
-            }"
-            @yKeyChanged="setYAxisKey"
-            @tickWidthChanged="onTickWidthChange"
-        />
+        <div
+            v-if="seriesModels.length"
+            class="u-contents"
+        >
+            <y-axis
+                v-for="(yAxis, index) in yAxesIds"
+                :id="yAxis.id"
+                :key="`yAxis-${index}`"
+                :multiple-left-axes="multipleLeftAxes"
+                :position="yAxis.id > 2 ? 'right' : 'left'"
+                :class="{'plot-yaxis-right': yAxis.id > 2}"
+                :tick-width="yAxis.tickWidth"
+                :plot-left-tick-width="yAxis.id > 2 ? yAxis.tickWidth: plotLeftTickWidth"
+                @yKeyChanged="setYAxisKey"
+                @tickWidthChanged="onTickWidthChange"
+            />
+        </div>
         <div
             class="gl-plot-wrapper-display-area-and-x-axis"
-            :style="{
-                left: (plotWidth + 20) + 'px'
-            }"
+            :style="xAxisStyle"
         >
 
             <div class="gl-plot-display-area has-local-controls has-cursor-guides">
@@ -69,9 +72,12 @@
                 />
 
                 <mct-ticks
+                    v-for="(yAxis, index) in yAxesIds"
                     v-show="gridLines"
+                    :key="`yAxis-gridlines-${index}`"
                     :axis-type="'yAxis'"
                     :position="'bottom'"
+                    :axis-id="yAxis.id"
                     @plotTickWidth="onTickWidthChange"
                 />
 
@@ -214,6 +220,7 @@ import YAxis from "./axis/YAxis.vue";
 import _ from "lodash";
 
 const OFFSET_THRESHOLD = 10;
+const AXES_PADDING = 20;
 
 export default {
     components: {
@@ -269,7 +276,6 @@ export default {
             altPressed: false,
             highlights: [],
             lockHighlightPoint: false,
-            tickWidth: 0,
             yKeyOptions: [],
             yAxisLabel: '',
             rectangles: [],
@@ -284,12 +290,31 @@ export default {
             isTimeOutOfSync: false,
             showLimitLineLabels: this.limitLineLabels,
             isFrozenOnMouseDown: false,
-            hasSameRangeValue: true,
             cursorGuide: this.initCursorGuide,
-            gridLines: this.initGridLines
+            gridLines: this.initGridLines,
+            yAxes: []
         };
     },
     computed: {
+        xAxisStyle() {
+            const rightAxis = this.yAxesIds.find(yAxis => yAxis.id > 2);
+            const leftOffset = this.multipleLeftAxes ? 2 * AXES_PADDING : AXES_PADDING;
+            let style = {
+                left: `${this.plotLeftTickWidth + leftOffset}px`
+            };
+
+            if (rightAxis) {
+                style.right = `${rightAxis.tickWidth + AXES_PADDING}px`;
+            }
+
+            return style;
+        },
+        yAxesIds() {
+            return this.yAxes.filter(yAxis => yAxis.seriesCount > 0);
+        },
+        multipleLeftAxes() {
+            return this.yAxes.filter(yAxis => yAxis.seriesCount > 0 && yAxis.id <= 2).length > 1;
+        },
         isNestedWithinAStackedPlot() {
             const isNavigatedObject = this.openmct.router.isNavigatedObject([this.domainObject].concat(this.path));
 
@@ -312,8 +337,17 @@ export default {
                 return 'plot-legend-collapsed';
             }
         },
-        plotWidth() {
-            return this.plotTickWidth || this.tickWidth;
+        plotLeftTickWidth() {
+            let leftTickWidth = 0;
+            this.yAxes.forEach((yAxis) => {
+                if (yAxis.id > 2) {
+                    return;
+                }
+
+                leftTickWidth = leftTickWidth + yAxis.tickWidth;
+            });
+
+            return this.plotTickWidth || leftTickWidth;
         }
     },
     watch: {
@@ -342,6 +376,20 @@ export default {
 
         this.config = this.getConfig();
         this.legend = this.config.legend;
+        this.yAxes = [{
+            id: this.config.yAxis.id,
+            seriesCount: 0,
+            tickWidth: 0
+        }];
+        if (this.config.additionalYAxes) {
+            this.yAxes = this.yAxes.concat(this.config.additionalYAxes.map(yAxis => {
+                return {
+                    id: yAxis.id,
+                    seriesCount: 0,
+                    tickWidth: 0
+                };
+            }));
+        }
 
         if (this.isNestedWithinAStackedPlot) {
             const configId = this.openmct.objects.makeKeyString(this.domainObject.identifier);
@@ -383,8 +431,10 @@ export default {
         },
         setTimeContext() {
             this.stopFollowingTimeContext();
+
             this.timeContext = this.openmct.time.getContextForView(this.path);
             this.followTimeContext();
+
         },
         followTimeContext() {
             this.updateDisplayBounds(this.timeContext.bounds());
@@ -417,12 +467,13 @@ export default {
             return config;
         },
         addSeries(series, index) {
+            const yAxisId = series.get('yAxisId');
+            this.updateAxisUsageCount(yAxisId, 1);
             this.$set(this.seriesModels, index, series);
             this.listenTo(series, 'change:xKey', (xKey) => {
                 this.setDisplayRange(series, xKey);
             }, this);
             this.listenTo(series, 'change:yKey', () => {
-                this.checkSameRangeValue();
                 this.loadSeriesData(series);
             }, this);
 
@@ -430,20 +481,21 @@ export default {
                 this.loadSeriesData(series);
             }, this);
 
-            this.checkSameRangeValue();
             this.loadSeriesData(series);
         },
 
-        checkSameRangeValue() {
-            this.hasSameRangeValue = this.seriesModels.every((model) => {
-                return model.get('yKey') === this.seriesModels[0].get('yKey');
-            });
+        removeSeries(plotSeries, index) {
+            const yAxisId = plotSeries.get('yAxisId');
+            this.updateAxisUsageCount(yAxisId, -1);
+            this.seriesModels.splice(index, 1);
+            this.stopListening(plotSeries);
         },
 
-        removeSeries(plotSeries, index) {
-            this.seriesModels.splice(index, 1);
-            this.checkSameRangeValue();
-            this.stopListening(plotSeries);
+        updateAxisUsageCount(yAxisId, updateCountBy) {
+            const foundYAxis = this.yAxes.find(yAxis => yAxis.id === yAxisId);
+            if (foundYAxis) {
+                foundYAxis.seriesCount = foundYAxis.seriesCount + updateCountBy;
+            }
         },
 
         loadSeriesData(series) {
@@ -673,6 +725,7 @@ export default {
 
             // Setup canvas etc.
             this.xScale = new LinearScale(this.config.xAxis.get('displayRange'));
+            //TODO: handle yScale, zoom/pan for all yAxes
             this.yScale = new LinearScale(this.config.yAxis.get('displayRange'));
 
             this.pan = undefined;
@@ -690,6 +743,9 @@ export default {
 
             this.listenTo(this.config.xAxis, 'change:displayRange', this.onXAxisChange, this);
             this.listenTo(this.config.yAxis, 'change:displayRange', this.onYAxisChange, this);
+            this.config.additionalYAxes.forEach(yAxis => {
+                this.listenTo(yAxis, 'change:displayRange', this.onYAxisChange, this);
+            });
         },
 
         onXAxisChange(displayBounds) {
@@ -704,20 +760,24 @@ export default {
             }
         },
 
-        onTickWidthChange(width, fromDifferentObject) {
-            if (fromDifferentObject) {
+        onTickWidthChange(data, fromDifferentObject) {
+            const {width, yAxisId} = data;
+            if (yAxisId) {
+                const index = this.yAxes.findIndex(yAxis => yAxis.id === yAxisId);
+                if (fromDifferentObject) {
                 // Always accept tick width if it comes from a different object.
-                this.tickWidth = width;
-            } else {
+                    this.yAxes[index].tickWidth = width;
+                } else {
                 // Otherwise, only accept tick with if it's larger.
-                const newWidth = Math.max(width, this.tickWidth);
-                if (newWidth !== this.tickWidth) {
-                    this.tickWidth = newWidth;
+                    const newWidth = Math.max(width, this.yAxes[index].tickWidth);
+                    if (newWidth !== this.yAxes[index].tickWidth) {
+                        this.yAxes[index].tickWidth = newWidth;
+                    }
                 }
-            }
 
-            const id = this.openmct.objects.makeKeyString(this.domainObject.identifier);
-            this.$emit('plotTickWidth', this.tickWidth, id);
+                const id = this.openmct.objects.makeKeyString(this.domainObject.identifier);
+                this.$emit('plotTickWidth', this.yAxes[index].tickWidth, id);
+            }
         },
 
         trackMousePosition(event) {
@@ -1108,8 +1168,9 @@ export default {
             this.userViewportChangeEnd();
         },
 
-        setYAxisKey(yKey) {
-            this.config.series.models[0].set('yKey', yKey);
+        setYAxisKey(yKey, yAxisId) {
+            const seriesForYAxis = this.config.series.models.filter((model => model.get('yAxisId') === yAxisId));
+            seriesForYAxis.forEach(model => model.set('yKey', yKey));
         },
 
         pause() {

src/plugins/plot/MctTicks.vue

@@ -103,6 +103,12 @@ export default {
                 return 6;
             }
         },
+        axisId: {
+            type: Number,
+            default() {
+                return null;
+            }
+        },
         position: {
             required: true,
             type: String,
@@ -145,7 +151,15 @@ export default {
                 throw new Error('config is missing');
             }
 
-            return config[this.axisType];
+            if (this.axisType === 'yAxis') {
+                if (this.axisId && this.axisId !== config.yAxis.id) {
+                    return config.additionalYAxes.find(axis => axis.id === this.axisId);
+                } else {
+                    return config.yAxis;
+                }
+            } else {
+                return config[this.axisType];
+            }
         },
         /**
        * Determine whether ticks should be regenerated for a given range.
@@ -258,7 +272,10 @@ export default {
                     }, 0));
 
                     this.tickWidth = tickWidth;
-                    this.$emit('plotTickWidth', tickWidth);
+                    this.$emit('plotTickWidth', {
+                        width: tickWidth,
+                        yAxisId: this.axisType === 'yAxis' ? this.axisId : ''
+                    });
                     this.shouldCheckWidth = false;
                 }
             }

src/plugins/plot/axis/YAxis.vue

@@ -22,10 +22,8 @@
 <template>
 <div
     v-if="loaded"
-    class="gl-plot-axis-area gl-plot-y has-local-controls"
-    :style="{
-        width: (tickWidth + 20) + 'px'
-    }"
+    class="gl-plot-axis-area gl-plot-y has-local-controls js-plot-y-axis"
+    :style="yAxisStyle"
 >
 
     <div
@@ -52,6 +50,7 @@
     </select>
 
     <mct-ticks
+        :axis-id="id"
         :axis-type="'yAxis'"
         class="gl-plot-ticks"
         :position="'top'"
@@ -63,6 +62,10 @@
 <script>
 import MctTicks from "../MctTicks.vue";
 import configStore from "../configuration/ConfigStore";
+import eventHelpers from "../lib/eventHelpers";
+
+const AXIS_PADDING = 20;
+const AXIS_OFFSET = 5;
 
 export default {
     components: {
@@ -70,22 +73,10 @@ export default {
     },
     inject: ['openmct', 'domainObject'],
     props: {
-        singleSeries: {
-            type: Boolean,
+        id: {
+            type: Number,
             default() {
-                return true;
-            }
-        },
-        hasSameRangeValue: {
-            type: Boolean,
-            default() {
-                return true;
-            }
-        },
-        seriesModel: {
-            type: Object,
-            default() {
-                return {};
+                return 1;
             }
         },
         tickWidth: {
@@ -93,37 +84,132 @@ export default {
             default() {
                 return 0;
             }
+        },
+        plotLeftTickWidth: {
+            type: Number,
+            default() {
+                return 0;
+            }
+        },
+        multipleLeftAxes: {
+            type: Boolean,
+            default() {
+                return false;
+            }
+        },
+        position: {
+            type: String,
+            default() {
+                return 'left';
+            }
         }
     },
     data() {
+        this.seriesModels = [];
+
         return {
             yAxisLabel: 'none',
-            loaded: false
+            loaded: false,
+            yKeyOptions: [],
+            hasSameRangeValue: true,
+            singleSeries: true,
+            mainYAxisId: null,
+            hasAdditionalYAxes: false
         };
     },
     computed: {
         canShowYAxisLabel() {
             return this.singleSeries === true || this.hasSameRangeValue === true;
+        },
+        yAxisStyle() {
+            let style = {
+                width: `${this.tickWidth + AXIS_PADDING}px`
+            };
+            const multipleAxesPadding = this.multipleLeftAxes ? AXIS_PADDING : 0;
+
+            if (this.position === 'right') {
+                style.left = `-${this.tickWidth + AXIS_PADDING}px`;
+            } else {
+                const thisIsTheSecondLeftAxis = (this.id - 1) > 0;
+                if (this.multipleLeftAxes && thisIsTheSecondLeftAxis) {
+                    style.left = `${ this.plotLeftTickWidth - this.tickWidth - multipleAxesPadding - AXIS_OFFSET }px`;
+                    style['border-right'] = `1px solid`;
+                } else {
+                    style.left = `${this.plotLeftTickWidth - this.tickWidth + multipleAxesPadding}px`;
+                }
+            }
+
+            return style;
         }
     },
     mounted() {
-        this.yAxis = this.getYAxisFromConfig();
+        eventHelpers.extend(this);
+        this.initAxisAndSeriesConfig();
         this.loaded = true;
         this.setUpYAxisOptions();
     },
     methods: {
-        getYAxisFromConfig() {
+        initAxisAndSeriesConfig() {
             const configId = this.openmct.objects.makeKeyString(this.domainObject.identifier);
             let config = configStore.get(configId);
             if (config) {
-                return config.yAxis;
+                this.mainYAxisId = config.yAxis.id;
+                this.hasAdditionalYAxes = config?.additionalYAxes.length;
+                if (this.id && this.id !== this.mainYAxisId) {
+                    this.yAxis = config.additionalYAxes.find(yAxis => yAxis.id === this.id);
+                } else {
+                    this.yAxis = config.yAxis;
+                }
+
+                this.config = config;
+                this.listenTo(this.config.series, 'add', this.addSeries, this);
+                this.listenTo(this.config.series, 'remove', this.removeSeries, this);
+                this.listenTo(this.config.series, 'reorder', this.addOrRemoveSeries, this);
+
+                this.config.series.models.forEach(this.addSeries, this);
             }
         },
+        addOrRemoveSeries(series) {
+            const yAxisId = this.series.get('yAxisId');
+            if (yAxisId === this.id) {
+                this.addSeries(series);
+            } else {
+                this.removeSeries(series);
+            }
+        },
+        addSeries(series, index) {
+            const yAxisId = series.get('yAxisId');
+            const seriesIndex = this.seriesModels.findIndex(model => this.openmct.objects.areIdsEqual(model.get('identifier'), series.get('identifier')));
+
+            if (yAxisId === this.id && seriesIndex < 0) {
+                this.seriesModels.push(series);
+                this.checkRangeValueAndSingleSeries();
+                this.setUpYAxisOptions();
+            }
+        },
+        removeSeries(plotSeries) {
+            const seriesIndex = this.seriesModels.findIndex(model => this.openmct.objects.areIdsEqual(model.get('identifier'), plotSeries.get('identifier')));
+            if (seriesIndex > -1) {
+                this.seriesModels.splice(seriesIndex, 1);
+                this.checkRangeValueAndSingleSeries();
+                this.setUpYAxisOptions();
+            }
+        },
+        checkRangeValueAndSingleSeries() {
+            this.hasSameRangeValue = this.seriesModels.every((model) => {
+                return model.get('yKey') === this.seriesModels[0].get('yKey');
+            });
+            this.singleSeries = this.seriesModels.length === 1;
+        },
         setUpYAxisOptions() {
             this.yKeyOptions = [];
+            if (!this.seriesModels.length) {
+                return;
+            }
 
-            if (this.seriesModel.metadata) {
-                this.yKeyOptions = this.seriesModel.metadata
+            const seriesModel = this.seriesModels[0];
+            if (seriesModel.metadata) {
+                this.yKeyOptions = seriesModel.metadata
                     .valuesForHints(['range'])
                     .map(function (o) {
                         return {
@@ -135,22 +221,22 @@ export default {
 
             //  set yAxisLabel if none is set yet
             if (this.yAxisLabel === 'none') {
-                let yKey = this.seriesModel.model.yKey;
-                let yKeyModel = this.yKeyOptions.filter(o => o.key === yKey)[0];
-
-                this.yAxisLabel = yKeyModel ? yKeyModel.name : '';
+                this.yAxisLabel = this.yAxis.get('label');
             }
         },
         toggleYAxisLabel() {
             let yAxisObject = this.yKeyOptions.filter(o => o.name === this.yAxisLabel)[0];
 
             if (yAxisObject) {
-                this.$emit('yKeyChanged', yAxisObject.key);
+                this.$emit('yKeyChanged', yAxisObject.key, this.id);
                 this.yAxis.set('label', this.yAxisLabel);
             }
         },
-        onTickWidthChange(width) {
-            this.$emit('tickWidthChanged', width);
+        onTickWidthChange(data) {
+            this.$emit('tickWidthChanged', {
+                width: data.width,
+                yAxisId: this.id
+            });
         }
     }
 };

src/plugins/plot/chart/MctChart.vue

@@ -98,7 +98,21 @@ export default {
         this.limitLines = [];
         this.pointSets = [];
         this.alarmSets = [];
-        this.offset = {};
+        const yAxisId = this.config.yAxis.get('id');
+        this.offset = {
+            [yAxisId]: {}
+        };
+        this.listenTo(this.config.yAxis, 'change:key', this.resetOffsetAndSeriesDataForYAxis.bind(this, yAxisId), this);
+        this.listenTo(this.config.yAxis, 'change', this.updateLimitsAndDraw);
+        if (this.config.additionalYAxes.length) {
+            this.config.additionalYAxes.forEach(yAxis => {
+                const id = yAxis.get('id');
+                this.offset[id] = {};
+                this.listenTo(yAxis, 'change', this.updateLimitsAndDraw);
+                this.listenTo(this.config.yAxis, 'change:key', this.resetOffsetAndSeriesDataForYAxis.bind(this, id), this);
+            });
+        }
+
         this.seriesElements = new WeakMap();
         this.seriesLimits = new WeakMap();
 
@@ -111,8 +125,7 @@ export default {
 
         this.listenTo(this.config.series, 'add', this.onSeriesAdd, this);
         this.listenTo(this.config.series, 'remove', this.onSeriesRemove, this);
-        this.listenTo(this.config.yAxis, 'change:key', this.clearOffset, this);
-        this.listenTo(this.config.yAxis, 'change', this.updateLimitsAndDraw);
+
         this.listenTo(this.config.xAxis, 'change', this.updateLimitsAndDraw);
         this.config.series.forEach(this.onSeriesAdd, this);
         this.$emit('chartLoaded');
@@ -224,25 +237,31 @@ export default {
             this.limitLines.forEach(line => line.destroy());
             DrawLoader.releaseDrawAPI(this.drawAPI);
         },
-        clearOffset() {
-            delete this.offset.x;
-            delete this.offset.y;
-            delete this.offset.xVal;
-            delete this.offset.yVal;
-            delete this.offset.xKey;
-            delete this.offset.yKey;
-            this.lines.forEach(function (line) {
+        resetOffsetAndSeriesDataForYAxis(yAxisId) {
+            delete this.offset[yAxisId].x;
+            delete this.offset[yAxisId].y;
+            delete this.offset[yAxisId].xVal;
+            delete this.offset[yAxisId].yVal;
+            delete this.offset[yAxisId].xKey;
+            delete this.offset[yAxisId].yKey;
+
+            const lines = this.lines.filter(this.matchByYAxisId.bind(this, yAxisId));
+            lines.forEach(function (line) {
                 line.reset();
             });
-            this.limitLines.forEach(function (line) {
+            const limitLines = this.limitLines.filter(this.matchByYAxisId.bind(this, yAxisId));
+            limitLines.forEach(function (line) {
                 line.reset();
             });
-            this.pointSets.forEach(function (pointSet) {
+            const pointSets = this.pointSets.filter(this.matchByYAxisId.bind(this, yAxisId));
+            pointSets.forEach(function (pointSet) {
                 pointSet.reset();
             });
         },
         setOffset(offsetPoint, index, series) {
-            if (this.offset.x && this.offset.y) {
+            const mainYAxisId = this.config.yAxis.get('id');
+            const yAxisId = series.get('yAxisId') || mainYAxisId;
+            if (this.offset[yAxisId].x && this.offset[yAxisId].y) {
                 return;
             }
 
@@ -251,19 +270,20 @@ export default {
                 y: series.getYVal(offsetPoint)
             };
 
-            this.offset.x = function (x) {
+            this.offset[yAxisId].x = function (x) {
                 return x - offsets.x;
             }.bind(this);
-            this.offset.y = function (y) {
+            this.offset[yAxisId].y = function (y) {
                 return y - offsets.y;
             }.bind(this);
-            this.offset.xVal = function (point, pSeries) {
-                return this.offset.x(pSeries.getXVal(point));
+            this.offset[yAxisId].xVal = function (point, pSeries) {
+                return this.offset[yAxisId].x(pSeries.getXVal(point));
             }.bind(this);
-            this.offset.yVal = function (point, pSeries) {
-                return this.offset.y(pSeries.getYVal(point));
+            this.offset[yAxisId].yVal = function (point, pSeries) {
+                return this.offset[yAxisId].y(pSeries.getYVal(point));
             }.bind(this);
         },
+
         initializeCanvas(canvas, overlay) {
             this.canvas = canvas;
             this.overlay = overlay;
@@ -311,11 +331,15 @@ export default {
             this.clearLimitLines(series);
         },
         lineForSeries(series) {
+            const mainYAxisId = this.config.yAxis.get('id');
+            const yAxisId = series.get('yAxisId') || mainYAxisId;
+            let offset = this.offset[yAxisId];
+
             if (series.get('interpolate') === 'linear') {
                 return new MCTChartLineLinear(
                     series,
                     this,
-                    this.offset
+                    offset
                 );
             }
 
@@ -323,33 +347,45 @@ export default {
                 return new MCTChartLineStepAfter(
                     series,
                     this,
-                    this.offset
+                    offset
                 );
             }
         },
         limitLineForSeries(series) {
+            const mainYAxisId = this.config.yAxis.get('id');
+            const yAxisId = series.get('yAxisId') || mainYAxisId;
+            let offset = this.offset[yAxisId];
+
             return new MCTChartAlarmLineSet(
                 series,
                 this,
-                this.offset,
+                offset,
                 this.openmct.time.bounds()
             );
         },
         pointSetForSeries(series) {
+            const mainYAxisId = this.config.yAxis.get('id');
+            const yAxisId = series.get('yAxisId') || mainYAxisId;
+            let offset = this.offset[yAxisId];
+
             if (series.get('markers')) {
                 return new MCTChartPointSet(
                     series,
                     this,
-                    this.offset
+                    offset
                 );
             }
         },
         alarmPointSetForSeries(series) {
+            const mainYAxisId = this.config.yAxis.get('id');
+            const yAxisId = series.get('yAxisId') || mainYAxisId;
+            let offset = this.offset[yAxisId];
+
             if (series.get('alarmMarkers')) {
                 return new MCTChartAlarmPointSet(
                     series,
                     this,
-                    this.offset
+                    offset
                 );
             }
         },
@@ -410,8 +446,8 @@ export default {
                 this.seriesLimits.delete(series);
             }
         },
-        canDraw() {
-            if (!this.offset.x || !this.offset.y) {
+        canDraw(yAxisId) {
+            if (!this.offset[yAxisId] || !this.offset[yAxisId].x || !this.offset[yAxisId].y) {
                 return false;
             }
 
@@ -434,16 +470,31 @@ export default {
             }
 
             this.drawAPI.clear();
-            if (this.canDraw()) {
-                this.updateViewport();
-                this.drawSeries();
-                this.drawRectangles();
-                this.drawHighlights();
-            }
+            const mainYAxisId = this.config.yAxis.get('id');
+            //There has to be at least one yAxis
+            const yAxisIds = [mainYAxisId].concat(this.config.additionalYAxes.map(yAxis => yAxis.get('id')));
+            // Repeat drawing for all yAxes
+            yAxisIds.forEach((id) => {
+                if (this.canDraw(id)) {
+                    this.updateViewport(id);
+                    this.drawSeries(id);
+                    this.drawRectangles(id);
+                    this.drawHighlights(id);
+                }
+            });
         },
-        updateViewport() {
+        updateViewport(yAxisId) {
+            const mainYAxisId = this.config.yAxis.get('id');
             const xRange = this.config.xAxis.get('displayRange');
-            const yRange = this.config.yAxis.get('displayRange');
+            let yRange;
+            if (yAxisId === mainYAxisId) {
+                yRange = this.config.yAxis.get('displayRange');
+            } else {
+                if (this.config.additionalYAxes.length) {
+                    const yAxisForId = this.config.additionalYAxes.find(yAxis => yAxis.get('id') === yAxisId);
+                    yRange = yAxisForId.get('displayRange');
+                }
+            }
 
             if (!xRange || !yRange) {
                 return;
@@ -454,9 +505,10 @@ export default {
                 yRange.max - yRange.min
             ];
 
-            const origin = [
-                this.offset.x(xRange.min),
-                this.offset.y(yRange.min)
+            let origin;
+            origin = [
+                this.offset[yAxisId].x(xRange.min),
+                this.offset[yAxisId].y(yRange.min)
             ];
 
             this.drawAPI.setDimensions(
@@ -464,38 +516,66 @@ export default {
                 origin
             );
         },
-        drawSeries() {
-            this.lines.forEach(this.drawLine, this);
-            this.pointSets.forEach(this.drawPoints, this);
-            this.alarmSets.forEach(this.drawAlarmPoints, this);
+        matchByYAxisId(id, item) {
+            const mainYAxisId = this.config.yAxis.get('id');
+            let matchesId = false;
+
+            const series = item.series;
+            if (series) {
+                const seriesYAxisId = series.get('yAxisId') || mainYAxisId;
+
+                matchesId = seriesYAxisId === id;
+            }
+
+            return matchesId;
+        },
+        drawSeries(id) {
+            const lines = this.lines.filter(this.matchByYAxisId.bind(this, id));
+            lines.forEach(this.drawLine, this);
+            const pointSets = this.pointSets.filter(this.matchByYAxisId.bind(this, id));
+            pointSets.forEach(this.drawPoints, this);
+            const alarmSets = this.alarmSets.filter(this.matchByYAxisId.bind(this, id));
+            alarmSets.forEach(this.drawAlarmPoints, this);
         },
         drawLimitLines() {
-            if (this.canDraw()) {
-                this.updateViewport();
-
-                if (!this.drawAPI.origin) {
-                    return;
-                }
-
-                Array.from(this.$refs.limitArea.children).forEach((el) => el.remove());
-                let limitPointOverlap = [];
-                this.limitLines.forEach((limitLine) => {
-                    let limitContainerEl = this.$refs.limitArea;
-                    limitLine.limits.forEach((limit) => {
-                        const showLabels = this.showLabels(limit.seriesKey);
-                        if (showLabels) {
-                            const overlap = this.getLimitOverlap(limit, limitPointOverlap);
-                            limitPointOverlap.push(overlap);
-                            let limitLabelEl = this.getLimitLabel(limit, overlap);
-                            limitContainerEl.appendChild(limitLabelEl);
-                        }
-
-                        let limitEl = this.getLimitElement(limit);
-                        limitContainerEl.appendChild(limitEl);
-
-                    }, this);
-                });
+            this.config.series.models.forEach(series => {
+                const yAxisId = series.get('yAxisId');
+                this.drawLimitLinesForSeries(yAxisId, series);
+            });
+        },
+        drawLimitLinesForSeries(yAxisId, series) {
+            if (!this.canDraw(yAxisId)) {
+                return;
             }
+
+            this.updateViewport(yAxisId);
+
+            if (!this.drawAPI.origin) {
+                return;
+            }
+
+            Array.from(this.$refs.limitArea.children).forEach((el) => el.remove());
+            let limitPointOverlap = [];
+            this.limitLines.forEach((limitLine) => {
+                let limitContainerEl = this.$refs.limitArea;
+                limitLine.limits.forEach((limit) => {
+                    if (!series.includes(limit.seriesKey)) {
+                        return;
+                    }
+
+                    const showLabels = this.showLabels(limit.seriesKey);
+                    if (showLabels) {
+                        const overlap = this.getLimitOverlap(limit, limitPointOverlap);
+                        limitPointOverlap.push(overlap);
+                        let limitLabelEl = this.getLimitLabel(limit, overlap);
+                        limitContainerEl.appendChild(limitLabelEl);
+                    }
+
+                    let limitEl = this.getLimitElement(limit);
+                    limitContainerEl.appendChild(limitEl);
+
+                }, this);
+            });
         },
         showLabels(seriesKey) {
             return this.showLimitLineLabels.seriesKey
@@ -577,22 +657,25 @@ export default {
             );
         },
         drawLine(chartElement, disconnected) {
-            this.drawAPI.drawLine(
-                chartElement.getBuffer(),
-                chartElement.color().asRGBAArray(),
-                chartElement.count,
-                disconnected
-            );
-        },
-        drawHighlights() {
-            if (this.highlights && this.highlights.length) {
-                this.highlights.forEach(this.drawHighlight, this);
+            if (chartElement) {
+                this.drawAPI.drawLine(
+                    chartElement.getBuffer(),
+                    chartElement.color().asRGBAArray(),
+                    chartElement.count,
+                    disconnected
+                );
             }
         },
-        drawHighlight(highlight) {
+        drawHighlights(yAxisId) {
+            if (this.highlights && this.highlights.length) {
+                const highlights = this.highlights.filter(this.matchByYAxisId.bind(this, yAxisId));
+                highlights.forEach(this.drawHighlight.bind(this, yAxisId), this);
+            }
+        },
+        drawHighlight(yAxisId, highlight) {
             const points = new Float32Array([
-                this.offset.xVal(highlight.point, highlight.series),
-                this.offset.yVal(highlight.point, highlight.series)
+                this.offset[yAxisId].xVal(highlight.point, highlight.series),
+                this.offset[yAxisId].yVal(highlight.point, highlight.series)
             ]);
 
             const color = highlight.series.get('color').asRGBAArray();
@@ -601,20 +684,21 @@ export default {
 
             this.drawAPI.drawPoints(points, color, pointCount, HIGHLIGHT_SIZE, shape);
         },
-        drawRectangles() {
+        drawRectangles(yAxisId) {
             if (this.rectangles) {
-                this.rectangles.forEach(this.drawRectangle, this);
+                const rectangles = this.rectangles.filter(this.matchByYAxisId.bind(this, yAxisId));
+                rectangles.forEach(this.drawRectangle.bind(this, yAxisId), this);
             }
         },
-        drawRectangle(rect) {
+        drawRectangle(yAxisId, rect) {
             this.drawAPI.drawSquare(
                 [
-                    this.offset.x(rect.start.x),
-                    this.offset.y(rect.start.y)
+                    this.offset[yAxisId].x(rect.start.x),
+                    this.offset[yAxisId].y(rect.start.y)
                 ],
                 [
-                    this.offset.x(rect.end.x),
-                    this.offset.y(rect.end.y)
+                    this.offset[yAxisId].x(rect.end.x),
+                    this.offset[yAxisId].y(rect.end.y)
                 ],
                 rect.color
             );

src/plugins/plot/configuration/PlotConfigurationModel.js

@@ -27,6 +27,10 @@ import XAxisModel from "./XAxisModel";
 import YAxisModel from "./YAxisModel";
 import LegendModel from "./LegendModel";
 
+const MAX_Y_AXES = 3;
+const MAIN_Y_AXES_ID = 1;
+const MAX_ADDITIONAL_AXES = MAX_Y_AXES - 1;
+
 /**
  * PlotConfiguration model stores the configuration of a plot and some
  * limited state.  The indiidual parts of the plot configuration model
@@ -58,8 +62,35 @@ export default class PlotConfigurationModel extends Model {
         this.yAxis = new YAxisModel({
             model: options.model.yAxis,
             plot: this,
-            openmct: options.openmct
+            openmct: options.openmct,
+            id: options.model.yAxis.id || MAIN_Y_AXES_ID
         });
+        //Add any axes in addition to the main yAxis above - we must always have at least 1 y-axis
+        //Addition axes ids will be the MAIN_Y_AXES_ID + x where x is between 1 and MAX_ADDITIONAL_AXES
+        this.additionalYAxes = [];
+        if (Array.isArray(options.model.additionalYAxes)) {
+            const maxLength = Math.min(MAX_ADDITIONAL_AXES, options.model.additionalYAxes.length);
+            for (let yAxisCount = 0; yAxisCount < maxLength; yAxisCount++) {
+                const yAxis = options.model.additionalYAxes[yAxisCount];
+                this.additionalYAxes.push(new YAxisModel({
+                    model: yAxis,
+                    plot: this,
+                    openmct: options.openmct,
+                    id: yAxis.id || (MAIN_Y_AXES_ID + yAxisCount + 1)
+                }));
+            }
+        }
+
+        // If the saved options config doesn't include information about all the additional axes, we initialize the remaining here
+        for (let axesCount = this.additionalYAxes.length; axesCount < MAX_ADDITIONAL_AXES; axesCount++) {
+            this.additionalYAxes.push(new YAxisModel({
+                plot: this,
+                openmct: options.openmct,
+                id: MAIN_Y_AXES_ID + axesCount + 1
+            }));
+        }
+        // end add additional axes
+
         this.legend = new LegendModel({
             model: options.model.legend,
             plot: this,
@@ -81,6 +112,9 @@ export default class PlotConfigurationModel extends Model {
         }
 
         this.yAxis.listenToSeriesCollection(this.series);
+        this.additionalYAxes.forEach(yAxis => {
+            yAxis.listenToSeriesCollection(this.series);
+        });
         this.legend.listenToSeriesCollection(this.series);
 
         this.listenTo(this, 'destroy', this.onDestroy, this);
@@ -145,6 +179,7 @@ export default class PlotConfigurationModel extends Model {
             domainObject: options.domainObject,
             xAxis: {},
             yAxis: _.cloneDeep(options.domainObject.configuration?.yAxis ?? {}),
+            additionalYAxes: _.cloneDeep(options.domainObject.configuration?.additionalYAxes ?? []),
             legend: _.cloneDeep(options.domainObject.configuration?.legend ?? {})
         };
     }

src/plugins/plot/configuration/PlotSeries.js

@@ -118,7 +118,8 @@ export default class PlotSeries extends Model {
             markerShape: 'point',
             markerSize: 2.0,
             alarmMarkers: true,
-            limitLines: false
+            limitLines: false,
+            yAxisId: options.model.yAxisId || 1
         };
     }
 

src/plugins/plot/configuration/YAxisModel.js

@@ -135,18 +135,44 @@ export default class YAxisModel extends Model {
         }
     }
     resetStats() {
+        //TODO: do we need the series id here?
         this.unset('stats');
-        this.seriesCollection.forEach(series => {
+        this.getSeriesForYAxis(this.seriesCollection).forEach(series => {
             if (series.has('stats')) {
                 this.updateStats(series.get('stats'));
             }
         });
     }
+    getSeriesForYAxis(seriesCollection) {
+        return seriesCollection.filter(series => {
+            const seriesYAxisId = series.get('yAxisId') || 1;
+
+            return seriesYAxisId === this.id;
+        });
+    }
+
+    getYAxisForId(id) {
+        const plotModel = this.plot.get('domainObject');
+        let yAxis;
+        if (this.id === 1) {
+            yAxis = plotModel.configuration?.yAxis;
+        } else {
+            if (plotModel.configuration?.additionalYAxes) {
+                yAxis = plotModel.configuration.additionalYAxes.find(additionalYAxis => additionalYAxis.id === id);
+            }
+        }
+
+        return yAxis;
+    }
     /**
      * @param {import('./PlotSeries').default} series
      */
     trackSeries(series) {
         this.listenTo(series, 'change:stats', seriesStats => {
+            if (series.get('yAxisId') !== this.id) {
+                return;
+            }
+
             if (!seriesStats) {
                 this.resetStats();
             } else {
@@ -154,6 +180,10 @@ export default class YAxisModel extends Model {
             }
         });
         this.listenTo(series, 'change:yKey', () => {
+            if (series.get('yAxisId') !== this.id) {
+                return;
+            }
+
             this.updateFromSeries(this.seriesCollection);
         });
     }
@@ -252,14 +282,40 @@ export default class YAxisModel extends Model {
         // Update the series collection labels and formatting
         this.updateFromSeries(this.seriesCollection);
     }
+
+    /**
+     * For a given series collection, get the metadata of the current yKey for each series.
+     * Then return first available value of the given property from the metadata.
+     * @param {import('./SeriesCollection').default} series
+     * @param {String} property
+     */
+    getMetadataValueByProperty(series, property) {
+        return series.map(s => (s.metadata ? s.metadata.value(s.get('yKey'))[property] : ''))
+            .reduce((a, b) => {
+                if (a === undefined) {
+                    return b;
+                }
+
+                if (a === b) {
+                    return a;
+                }
+
+                return '';
+            }, undefined);
+    }
     /**
      * Update yAxis format, values, and label from known series.
      * @param {import('./SeriesCollection').default} seriesCollection
      */
     updateFromSeries(seriesCollection) {
-        const plotModel = this.plot.get('domainObject');
-        const label = plotModel.configuration?.yAxis?.label;
-        const sampleSeries = seriesCollection.first();
+        const seriesForThisYAxis = this.getSeriesForYAxis(seriesCollection);
+        if (!seriesForThisYAxis.length) {
+            return;
+        }
+
+        const yAxis = this.getYAxisForId(this.id);
+        const label = yAxis?.label;
+        const sampleSeries = seriesForThisYAxis[0];
         if (!sampleSeries || !sampleSeries.metadata) {
             if (!label) {
                 this.unset('label');
@@ -279,41 +335,17 @@ export default class YAxisModel extends Model {
         }
 
         this.set('values', yMetadata.values);
+
         if (!label) {
-            const labelName = seriesCollection
-                .map(s => (s.metadata ? s.metadata.value(s.get('yKey')).name : ''))
-                .reduce((a, b) => {
-                    if (a === undefined) {
-                        return b;
-                    }
-
-                    if (a === b) {
-                        return a;
-                    }
-
-                    return '';
-                }, undefined);
-
+            const labelName = this.getMetadataValueByProperty(seriesForThisYAxis, 'name');
             if (labelName) {
                 this.set('label', labelName);
 
                 return;
             }
 
-            const labelUnits = seriesCollection
-                .map(s => (s.metadata ? s.metadata.value(s.get('yKey')).units : ''))
-                .reduce((a, b) => {
-                    if (a === undefined) {
-                        return b;
-                    }
-
-                    if (a === b) {
-                        return a;
-                    }
-
-                    return '';
-                }, undefined);
-
+            //if the name is not available, set the units as the label
+            const labelUnits = this.getMetadataValueByProperty(seriesForThisYAxis, 'units');
             if (labelUnits) {
                 this.set('label', labelUnits);
 
@@ -331,7 +363,8 @@ export default class YAxisModel extends Model {
             frozen: false,
             autoscale: true,
             logMode: options.model?.logMode ?? false,
-            autoscalePadding: 0.1
+            autoscalePadding: 0.1,
+            id: options.id
 
             // 'range' is not specified here, it is undefined at first. When the
             // user turns off autoscale, the current 'displayRange' is used for

src/plugins/plot/inspector/PlotOptionsBrowse.vue

@@ -36,20 +36,21 @@
         />
     </ul>
     <div
-        v-if="plotSeries.length"
+        v-if="plotSeries.length && !isStackedPlotObject"
         class="grid-properties"
     >
         <ul
-            v-if="!isStackedPlotObject"
+            v-for="(yAxis, index) in yAxesWithSeries"
+            :key="`yAxis-${index}`"
             class="l-inspector-part js-yaxis-properties"
         >
-            <h2 title="Y axis settings for this object">Y Axis</h2>
+            <h2 title="Y axis settings for this object">Y Axis {{ yAxis.id }}</h2>
             <li class="grid-row">
                 <div
                     class="grid-cell label"
                     title="Manually override how the Y axis is labeled."
                 >Label</div>
-                <div class="grid-cell value">{{ label ? label : "Not defined" }}</div>
+                <div class="grid-cell value">{{ yAxis.label ? yAxis.label : "Not defined" }}</div>
             </li>
             <li class="grid-row">
                 <div
@@ -57,7 +58,7 @@
                     title="Enable log mode."
                 >Log mode</div>
                 <div class="grid-cell value">
-                    {{ logMode ? "Enabled" : "Disabled" }}
+                    {{ yAxis.logMode ? "Enabled" : "Disabled" }}
                 </div>
             </li>
             <li class="grid-row">
@@ -66,32 +67,36 @@
                     title="Automatically scale the Y axis to keep all values in view."
                 >Auto scale</div>
                 <div class="grid-cell value">
-                    {{ autoscale ? "Enabled: " + autoscalePadding : "Disabled" }}
+                    {{ yAxis.autoscale ? "Enabled: " + yAxis.autoscalePadding : "Disabled" }}
                 </div>
             </li>
             <li
-                v-if="!autoscale && rangeMin"
+                v-if="!yAxis.autoscale && yAxis.rangeMin"
                 class="grid-row"
             >
                 <div
                     class="grid-cell label"
                     title="Minimum Y axis value."
                 >Minimum value</div>
-                <div class="grid-cell value">{{ rangeMin }}</div>
+                <div class="grid-cell value">{{ yAxis.rangeMin }}</div>
             </li>
             <li
-                v-if="!autoscale && rangeMax"
+                v-if="!yAxis.autoscale && yAxis.rangeMax"
                 class="grid-row"
             >
                 <div
                     class="grid-cell label"
                     title="Maximum Y axis value."
                 >Maximum value</div>
-                <div class="grid-cell value">{{ rangeMax }}</div>
+                <div class="grid-cell value">{{ yAxis.rangeMax }}</div>
             </li>
         </ul>
+    </div>
+    <div
+        v-if="plotSeries.length && (isStackedPlotObject || !isNestedWithinAStackedPlot)"
+        class="grid-properties"
+    >
         <ul
-            v-if="isStackedPlotObject || !isNestedWithinAStackedPlot"
             class="l-inspector-part js-legend-properties"
         >
             <h2 title="Legend settings for this object">Legend</h2>
@@ -157,12 +162,6 @@ export default {
     data() {
         return {
             config: {},
-            label: '',
-            autoscale: '',
-            logMode: false,
-            autoscalePadding: '',
-            rangeMin: '',
-            rangeMax: '',
             position: '',
             hideLegendWhenSmall: '',
             expandByDefault: '',
@@ -173,7 +172,8 @@ export default {
             showMaximumWhenExpanded: '',
             showUnitsWhenExpanded: '',
             loaded: false,
-            plotSeries: []
+            plotSeries: [],
+            yAxes: []
         };
     },
     computed: {
@@ -182,13 +182,18 @@ export default {
         },
         isStackedPlotObject() {
             return this.path.find((pathObject, pathObjIndex) => pathObjIndex === 0 && pathObject.type === 'telemetry.plot.stacked');
+        },
+        yAxesWithSeries() {
+            return this.yAxes.filter(yAxis => yAxis.seriesCount > 0);
         }
     },
     mounted() {
         eventHelpers.extend(this);
         this.config = this.getConfig();
+        this.initYAxesConfiguration();
+
         this.registerListeners();
-        this.initConfiguration();
+        this.initLegendConfiguration();
         this.loaded = true;
 
     },
@@ -196,18 +201,38 @@ export default {
         this.stopListening();
     },
     methods: {
-        initConfiguration() {
+        initYAxesConfiguration() {
             if (this.config) {
-                this.label = this.config.yAxis.get('label');
-                this.autoscale = this.config.yAxis.get('autoscale');
-                this.logMode = this.config.yAxis.get('logMode');
-                this.autoscalePadding = this.config.yAxis.get('autoscalePadding');
-                const range = this.config.yAxis.get('range');
-                if (range) {
-                    this.rangeMin = range.min;
-                    this.rangeMax = range.max;
-                }
+                let range = this.config.yAxis.get('range');
 
+                this.yAxes.push({
+                    id: this.config.yAxis.id,
+                    seriesCount: 0,
+                    label: this.config.yAxis.get('label'),
+                    autoscale: this.config.yAxis.get('autoscale'),
+                    logMode: this.config.yAxis.get('logMode'),
+                    autoscalePadding: this.config.yAxis.get('autoscalePadding'),
+                    rangeMin: range ? range.min : '',
+                    rangeMax: range ? range.max : ''
+                });
+                this.config.additionalYAxes.forEach(yAxis => {
+                    range = yAxis.get('range');
+
+                    this.yAxes.push({
+                        id: yAxis.id,
+                        seriesCount: 0,
+                        label: yAxis.get('label'),
+                        autoscale: yAxis.get('autoscale'),
+                        logMode: yAxis.get('logMode'),
+                        autoscalePadding: yAxis.get('autoscalePadding'),
+                        rangeMin: range ? range.min : '',
+                        rangeMax: range ? range.max : ''
+                    });
+                });
+            }
+        },
+        initLegendConfiguration() {
+            if (this.config) {
                 this.position = this.config.legend.get('position');
                 this.hideLegendWhenSmall = this.config.legend.get('hideLegendWhenSmall');
                 this.expandByDefault = this.config.legend.get('expandByDefault');
@@ -229,18 +254,44 @@ export default {
                 this.config.series.forEach(this.addSeries, this);
 
                 this.listenTo(this.config.series, 'add', this.addSeries, this);
-                this.listenTo(this.config.series, 'remove', this.resetAllSeries, this);
+                this.listenTo(this.config.series, 'remove', this.removeSeries, this);
+            }
+        },
+
+        setYAxisLabel(yAxisId) {
+            const found = this.yAxes.find(yAxis => yAxis.id === yAxisId);
+            if (found && found.seriesCount > 0) {
+                const mainYAxisId = this.config.yAxis.id;
+                if (mainYAxisId === yAxisId) {
+                    found.label = this.config.yAxis.get('label');
+                } else {
+                    const additionalYAxis = this.config.additionalYAxes.find(axis => axis.id === yAxisId);
+                    if (additionalYAxis) {
+                        found.label = additionalYAxis.get('label');
+                    }
+                }
             }
         },
 
         addSeries(series, index) {
+            const yAxisId = series.get('yAxisId');
+            this.updateAxisUsageCount(yAxisId, 1);
             this.$set(this.plotSeries, index, series);
-            this.initConfiguration();
+            this.setYAxisLabel(yAxisId);
         },
 
-        resetAllSeries() {
-            this.plotSeries = [];
-            this.config.series.forEach(this.addSeries, this);
+        removeSeries(plotSeries, index) {
+            const yAxisId = plotSeries.get('yAxisId');
+            this.updateAxisUsageCount(yAxisId, -1);
+            this.plotSeries.splice(index, 1);
+            this.setYAxisLabel(yAxisId);
+        },
+
+        updateAxisUsageCount(yAxisId, updateCount) {
+            const foundYAxis = this.yAxes.find(yAxis => yAxis.id === yAxisId);
+            if (foundYAxis) {
+                foundYAxis.seriesCount = foundYAxis.seriesCount + updateCount;
+            }
         }
     }
 };

src/plugins/plot/inspector/PlotOptionsEdit.vue

@@ -40,8 +40,10 @@
         </li>
     </ul>
     <y-axis-form
-        v-if="plotSeries.length && !isStackedPlotObject"
-        class="grid-properties"
+        v-for="(yAxisId, index) in yAxesIds"
+        :id="yAxisId.id"
+        :key="`yAxis-${index}`"
+        class="grid-properties js-yaxis-grid-properties"
         :y-axis="config.yAxis"
         @seriesUpdated="updateSeriesConfigForObject"
     />
@@ -76,6 +78,7 @@ export default {
     data() {
         return {
             config: {},
+            yAxes: [],
             plotSeries: [],
             loaded: false
         };
@@ -86,11 +89,27 @@ export default {
         },
         isStackedPlotObject() {
             return this.path.find((pathObject, pathObjIndex) => pathObjIndex === 0 && pathObject.type === 'telemetry.plot.stacked');
+        },
+        yAxesIds() {
+            return !this.isStackedPlotObject && this.yAxes.filter(yAxis => yAxis.seriesCount > 0);
         }
     },
     mounted() {
         eventHelpers.extend(this);
         this.config = this.getConfig();
+        this.yAxes = [{
+            id: this.config.yAxis.id,
+            seriesCount: 0
+        }];
+        if (this.config.additionalYAxes) {
+            this.yAxes = this.yAxes.concat(this.config.additionalYAxes.map(yAxis => {
+                return {
+                    id: yAxis.id,
+                    seriesCount: 0
+                };
+            }));
+        }
+
         this.registerListeners();
         this.loaded = true;
     },
@@ -107,16 +126,47 @@ export default {
             this.config.series.forEach(this.addSeries, this);
 
             this.listenTo(this.config.series, 'add', this.addSeries, this);
-            this.listenTo(this.config.series, 'remove', this.resetAllSeries, this);
+            this.listenTo(this.config.series, 'remove', this.removeSeries, this);
+        },
+
+        findYAxisForId(yAxisId) {
+            return this.yAxes.find(yAxis => yAxis.id === yAxisId);
+        },
+
+        setYAxisLabel(yAxisId) {
+            const found = this.findYAxisForId(yAxisId);
+            if (found && found.seriesCount > 0) {
+                const mainYAxisId = this.config.yAxis.id;
+                if (mainYAxisId === yAxisId) {
+                    found.label = this.config.yAxis.get('label');
+                } else {
+                    const additionalYAxis = this.config.additionalYAxes.find(axis => axis.id === yAxisId);
+                    if (additionalYAxis) {
+                        found.label = additionalYAxis.get('label');
+                    }
+                }
+            }
         },
 
         addSeries(series, index) {
+            const yAxisId = series.get('yAxisId');
+            this.updateAxisUsageCount(yAxisId, 1);
             this.$set(this.plotSeries, index, series);
+            this.setYAxisLabel(yAxisId);
         },
 
-        resetAllSeries() {
-            this.plotSeries = [];
-            this.config.series.forEach(this.addSeries, this);
+        removeSeries(series, index) {
+            const yAxisId = series.get('yAxisId');
+            this.updateAxisUsageCount(yAxisId, -1);
+            this.plotSeries.splice(index, 1);
+            this.setYAxisLabel(yAxisId);
+        },
+
+        updateAxisUsageCount(yAxisId, updateCount) {
+            const foundYAxis = this.findYAxisForId(yAxisId);
+            if (foundYAxis) {
+                foundYAxis.seriesCount = foundYAxis.seriesCount + updateCount;
+            }
         },
 
         updateSeriesConfigForObject(config) {

src/plugins/plot/inspector/forms/YAxisForm.vue

@@ -1,7 +1,7 @@
 <template>
-<div>
+<div v-if="loaded">
     <ul class="l-inspector-part">
-        <h2>Y Axis</h2>
+        <h2>Y Axis {{ id }}</h2>
         <li class="grid-row">
             <div
                 class="grid-cell label"
@@ -25,6 +25,7 @@
                 <!-- eslint-disable-next-line vue/html-self-closing -->
                 <input
                     v-model="logMode"
+                    class="js-log-mode-input"
                     type="checkbox"
                     @change="updateForm('logMode')"
                 />
@@ -103,52 +104,72 @@
 <script>
 import { objectPath } from "./formUtil";
 import _ from "lodash";
+import eventHelpers from "../../lib/eventHelpers";
+import configStore from "../../configuration/ConfigStore";
 
 export default {
     inject: ['openmct', 'domainObject'],
     props: {
-        yAxis: {
-            type: Object,
-            default() {
-                return {};
-            }
+        id: {
+            type: Number,
+            required: true
         }
     },
     data() {
         return {
+            yAxis: null,
             label: '',
             autoscale: '',
             logMode: false,
             autoscalePadding: '',
             rangeMin: '',
             rangeMax: '',
-            validationErrors: {}
+            validationErrors: {},
+            loaded: false
         };
     },
     mounted() {
-        this.initialize();
+        eventHelpers.extend(this);
+        this.getConfig();
+        this.loaded = true;
+        this.initFields();
         this.initFormValues();
     },
     methods: {
-        initialize: function () {
+        getConfig() {
+            const configId = this.openmct.objects.makeKeyString(this.domainObject.identifier);
+            const config = configStore.get(configId);
+            if (config) {
+                const mainYAxisId = config.yAxis.id;
+                this.isAdditionalYAxis = this.id !== mainYAxisId;
+                if (this.isAdditionalYAxis) {
+                    this.additionalYAxes = config.additionalYAxes;
+                    this.yAxis = config.additionalYAxes.find(yAxis => yAxis.id === this.id);
+                } else {
+                    this.yAxis = config.yAxis;
+                }
+            }
+        },
+        initFields() {
+            const prefix = `configuration.${this.getPrefix()}`;
             this.fields = {
                 label: {
-                    objectPath: 'configuration.yAxis.label'
+                    objectPath: `${prefix}.label`
                 },
                 autoscale: {
                     coerce: Boolean,
-                    objectPath: 'configuration.yAxis.autoscale'
+                    objectPath: `${prefix}.autoscale`
                 },
                 autoscalePadding: {
                     coerce: Number,
-                    objectPath: 'configuration.yAxis.autoscalePadding'
+                    objectPath: `${prefix}.autoscalePadding`
                 },
                 logMode: {
                     coerce: Boolean,
-                    objectPath: 'configuration.yAxis.logMode'
+                    objectPath: `${prefix}.logMode`
                 },
                 range: {
-                    objectPath: 'configuration.yAxis.range',
+                    objectPath: `${prefix}.range'`,
                     coerce: function coerceRange(range) {
                         const newRange = {
                             min: -1,
@@ -202,6 +223,25 @@ export default {
             this.rangeMin = range?.min;
             this.rangeMax = range?.max;
         },
+        getPrefix() {
+            let prefix = 'yAxis';
+            if (this.isAdditionalYAxis) {
+                let index = -1;
+                if (this.additionalYAxes) {
+                    index = this.additionalYAxes.findIndex((yAxis) => {
+                        return yAxis.id === this.id;
+                    });
+                }
+
+                if (index < 0) {
+                    index = 0;
+                }
+
+                prefix = `additionalYAxes[${index}]`;
+            }
+
+            return prefix;
+        },
         updateForm(formKey) {
             let newVal;
             if (formKey === 'range') {
@@ -231,18 +271,42 @@ export default {
                 this.yAxis.set(formKey, newVal);
                 // Then we mutate the domain object configuration to persist the settings
                 if (path) {
-                    if (!this.domainObject.configuration || !this.domainObject.configuration.series) {
-                        this.$emit('seriesUpdated', {
-                            identifier: this.domainObject.identifier,
-                            path: `yAxis.${formKey}`,
-                            value: newVal
-                        });
+                    if (this.isAdditionalYAxis) {
+                        if (this.domainObject.configuration && this.domainObject.configuration.series) {
+                            //update the id
+                            this.openmct.objects.mutate(
+                                this.domainObject,
+                                `configuration.${this.getPrefix()}.id`,
+                                this.id
+                            );
+                            //update the yAxes values
+                            this.openmct.objects.mutate(
+                                this.domainObject,
+                                path(this.domainObject, this.yAxis),
+                                newVal
+                            );
+                        } else {
+                            this.$emit('seriesUpdated', {
+                                identifier: this.domainObject.identifier,
+                                path: `${this.getPrefix()}.${formKey}`,
+                                id: this.id,
+                                value: newVal
+                            });
+                        }
                     } else {
-                        this.openmct.objects.mutate(
-                            this.domainObject,
-                            path(this.domainObject, this.yAxis),
-                            newVal
-                        );
+                        if (this.domainObject.configuration && this.domainObject.configuration.series) {
+                            this.openmct.objects.mutate(
+                                this.domainObject,
+                                path(this.domainObject, this.yAxis),
+                                newVal
+                            );
+                        } else {
+                            this.$emit('seriesUpdated', {
+                                identifier: this.domainObject.identifier,
+                                path: `${this.getPrefix()}.${formKey}`,
+                                value: newVal
+                            });
+                        }
                     }
                 }
             }

src/plugins/plot/overlayPlot/pluginSpec.js

@@ -0,0 +1,504 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2022, 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 {createMouseEvent, createOpenMct, resetApplicationState, spyOnBuiltins} from "utils/testing";
+import PlotVuePlugin from "../plugin";
+import Vue from "vue";
+import Plot from "../Plot.vue";
+import configStore from "../configuration/ConfigStore";
+import EventEmitter from "EventEmitter";
+import PlotOptions from "../inspector/PlotOptions.vue";
+
+describe("the plugin", function () {
+    let element;
+    let child;
+    let openmct;
+    let telemetryPromise;
+    let telemetryPromiseResolve;
+    let mockObjectPath;
+    let overlayPlotObject = {
+        identifier: {
+            namespace: "",
+            key: "test-plot"
+        },
+        type: "telemetry.plot.overlay",
+        name: "Test Overlay Plot",
+        composition: [],
+        configuration: {
+            series: []
+        }
+    };
+
+    beforeEach((done) => {
+        mockObjectPath = [
+            {
+                name: 'mock folder',
+                type: 'fake-folder',
+                identifier: {
+                    key: 'mock-folder',
+                    namespace: ''
+                }
+            },
+            {
+                name: 'mock parent folder',
+                type: 'time-strip',
+                identifier: {
+                    key: 'mock-parent-folder',
+                    namespace: ''
+                }
+            }
+        ];
+        const testTelemetry = [
+            {
+                'utc': 1,
+                'some-key': 'some-value 1',
+                'some-other-key': 'some-other-value 1',
+                'some-key2': 'some-value2 1',
+                'some-other-key2': 'some-other-value2 1'
+            },
+            {
+                'utc': 2,
+                'some-key': 'some-value 2',
+                'some-other-key': 'some-other-value 2',
+                'some-key2': 'some-value2 2',
+                'some-other-key2': 'some-other-value2 2'
+            },
+            {
+                'utc': 3,
+                'some-key': 'some-value 3',
+                'some-other-key': 'some-other-value 3',
+                'some-key2': 'some-value2 2',
+                'some-other-key2': 'some-other-value2 2'
+            }
+        ];
+
+        const timeSystem = {
+            timeSystemKey: 'utc',
+            bounds: {
+                start: 0,
+                end: 4
+            }
+        };
+
+        openmct = createOpenMct(timeSystem);
+
+        telemetryPromise = new Promise((resolve) => {
+            telemetryPromiseResolve = resolve;
+        });
+
+        spyOn(openmct.telemetry, 'request').and.callFake(() => {
+            telemetryPromiseResolve(testTelemetry);
+
+            return telemetryPromise;
+        });
+
+        openmct.install(new PlotVuePlugin());
+
+        element = document.createElement("div");
+        element.style.width = "640px";
+        element.style.height = "480px";
+        child = document.createElement("div");
+        child.style.width = "640px";
+        child.style.height = "480px";
+        element.appendChild(child);
+        document.body.appendChild(element);
+
+        spyOn(window, 'ResizeObserver').and.returnValue({
+            observe() {},
+            unobserve() {},
+            disconnect() {}
+        });
+
+        openmct.types.addType("test-object", {
+            creatable: true
+        });
+
+        spyOnBuiltins(["requestAnimationFrame"]);
+        window.requestAnimationFrame.and.callFake((callBack) => {
+            callBack();
+        });
+
+        openmct.router.path = [overlayPlotObject];
+        openmct.on("start", done);
+        openmct.startHeadless();
+    });
+
+    afterEach((done) => {
+        openmct.time.timeSystem('utc', {
+            start: 0,
+            end: 1
+        });
+        configStore.deleteAll();
+        resetApplicationState(openmct).then(done).catch(done);
+    });
+
+    afterAll(() => {
+        openmct.router.path = null;
+    });
+
+    describe("the plot views", () => {
+        it("provides an overlay plot view for objects with telemetry", () => {
+            const testTelemetryObject = {
+                id: "test-object",
+                type: "telemetry.plot.overlay",
+                telemetry: {
+                    values: [{
+                        key: "some-key"
+                    }]
+                }
+            };
+
+            const applicableViews = openmct.objectViews.get(testTelemetryObject, mockObjectPath);
+            let plotView = applicableViews.find((viewProvider) => viewProvider.key === "plot-overlay");
+            expect(plotView).toBeDefined();
+        });
+
+    });
+
+    describe("The overlay plot view with multiple axes", () => {
+        let testTelemetryObject;
+        let testTelemetryObject2;
+        let config;
+        let component;
+        let mockComposition;
+
+        afterAll(() => {
+            component.$destroy();
+            openmct.router.path = null;
+        });
+
+        beforeEach(() => {
+            testTelemetryObject = {
+                identifier: {
+                    namespace: "",
+                    key: "test-object"
+                },
+                type: "test-object",
+                name: "Test Object",
+                telemetry: {
+                    values: [{
+                        key: "utc",
+                        format: "utc",
+                        name: "Time",
+                        hints: {
+                            domain: 1
+                        }
+                    }, {
+                        key: "some-key",
+                        name: "Some attribute",
+                        hints: {
+                            range: 1
+                        }
+                    }, {
+                        key: "some-other-key",
+                        name: "Another attribute",
+                        hints: {
+                            range: 2
+                        }
+                    }]
+                }
+            };
+
+            testTelemetryObject2 = {
+                identifier: {
+                    namespace: "",
+                    key: "test-object2"
+                },
+                type: "test-object",
+                name: "Test Object2",
+                telemetry: {
+                    values: [{
+                        key: "utc",
+                        format: "utc",
+                        name: "Time",
+                        hints: {
+                            domain: 1
+                        }
+                    }, {
+                        key: "some-key2",
+                        name: "Some attribute2",
+                        hints: {
+                            range: 1
+                        }
+                    }, {
+                        key: "some-other-key2",
+                        name: "Another attribute2",
+                        hints: {
+                            range: 2
+                        }
+                    }]
+                }
+            };
+            overlayPlotObject.composition = [
+                {
+                    identifier: testTelemetryObject.identifier
+                },
+                {
+                    identifier: testTelemetryObject2.identifier
+                }
+            ];
+            overlayPlotObject.configuration.series = [
+                {
+                    identifier: testTelemetryObject.identifier,
+                    yAxisId: 1
+                },
+                {
+                    identifier: testTelemetryObject2.identifier,
+                    yAxisId: 3
+                }
+            ];
+            overlayPlotObject.configuration.additionalYAxes = [
+                {
+                    label: 'Test Object Label',
+                    id: 2
+                },
+                {
+                    label: 'Test Object 2 Label',
+                    id: 3
+                }
+            ];
+            mockComposition = new EventEmitter();
+            mockComposition.load = () => {
+                mockComposition.emit('add', testTelemetryObject);
+                mockComposition.emit('add', testTelemetryObject2);
+
+                return [testTelemetryObject, testTelemetryObject2];
+            };
+
+            spyOn(openmct.composition, 'get').and.returnValue(mockComposition);
+
+            let viewContainer = document.createElement("div");
+            child.append(viewContainer);
+            component = new Vue({
+                el: viewContainer,
+                components: {
+                    Plot
+                },
+                provide: {
+                    openmct: openmct,
+                    domainObject: overlayPlotObject,
+                    composition: openmct.composition.get(overlayPlotObject),
+                    path: [overlayPlotObject]
+                },
+                template: '<plot ref="plotComponent"></plot>'
+            });
+
+            return telemetryPromise
+                .then(Vue.nextTick())
+                .then(() => {
+                    const configId = openmct.objects.makeKeyString(overlayPlotObject.identifier);
+                    config = configStore.get(configId);
+                });
+        });
+
+        it("Renders multiple Y-axis for the telemetry objects", (done) => {
+            config.yAxis.set('displayRange', {
+                min: 10,
+                max: 20
+            });
+            Vue.nextTick(() => {
+                let yAxisElement = element.querySelectorAll(".gl-plot-axis-area.gl-plot-y .gl-plot-tick-wrapper");
+                expect(yAxisElement.length).toBe(2);
+                done();
+            });
+        });
+
+        describe('the inspector view', () => {
+            let inspectorComponent;
+            let viewComponentObject;
+            let selection;
+            beforeEach((done) => {
+                selection = [
+                    [
+                        {
+                            context: {
+                                item: {
+                                    id: overlayPlotObject.identifier.key,
+                                    identifier: overlayPlotObject.identifier,
+                                    type: overlayPlotObject.type,
+                                    configuration: overlayPlotObject.configuration,
+                                    composition: overlayPlotObject.composition
+                                }
+                            }
+                        }
+                    ]
+                ];
+
+                let viewContainer = document.createElement('div');
+                child.append(viewContainer);
+                inspectorComponent = new Vue({
+                    el: viewContainer,
+                    components: {
+                        PlotOptions
+                    },
+                    provide: {
+                        openmct: openmct,
+                        domainObject: selection[0][0].context.item,
+                        path: [selection[0][0].context.item]
+                    },
+                    template: '<plot-options/>'
+                });
+
+                Vue.nextTick(() => {
+                    viewComponentObject = inspectorComponent.$root.$children[0];
+                    done();
+                });
+            });
+
+            afterEach(() => {
+                openmct.router.path = null;
+            });
+
+            describe('in edit mode', () => {
+                let editOptionsEl;
+
+                beforeEach((done) => {
+                    viewComponentObject.setEditState(true);
+                    Vue.nextTick(() => {
+                        editOptionsEl = viewComponentObject.$el.querySelector('.js-plot-options-edit');
+                        done();
+                    });
+                });
+
+                it('shows multiple yAxis options', () => {
+                    const yAxisProperties = editOptionsEl.querySelectorAll(".js-yaxis-grid-properties .l-inspector-part h2");
+                    expect(yAxisProperties.length).toEqual(2);
+                });
+
+                it('saves yAxis options', () => {
+                    //toggle log mode and save
+                    config.additionalYAxes[1].set('displayRange', {
+                        min: 10,
+                        max: 20
+                    });
+                    const yAxisProperties = editOptionsEl.querySelectorAll(".js-log-mode-input");
+                    const clickEvent = createMouseEvent("click");
+                    yAxisProperties[1].dispatchEvent(clickEvent);
+
+                    expect(config.additionalYAxes[1].get('logMode')).toEqual(true);
+
+                });
+            });
+
+        });
+
+    });
+
+    describe("The overlay plot view with single axes", () => {
+        let testTelemetryObject;
+        let config;
+        let component;
+        let mockComposition;
+
+        afterAll(() => {
+            component.$destroy();
+            openmct.router.path = null;
+        });
+
+        beforeEach(() => {
+            testTelemetryObject = {
+                identifier: {
+                    namespace: "",
+                    key: "test-object"
+                },
+                type: "test-object",
+                name: "Test Object",
+                telemetry: {
+                    values: [{
+                        key: "utc",
+                        format: "utc",
+                        name: "Time",
+                        hints: {
+                            domain: 1
+                        }
+                    }, {
+                        key: "some-key",
+                        name: "Some attribute",
+                        hints: {
+                            range: 1
+                        }
+                    }, {
+                        key: "some-other-key",
+                        name: "Another attribute",
+                        hints: {
+                            range: 2
+                        }
+                    }]
+                }
+            };
+
+            overlayPlotObject.composition = [
+                {
+                    identifier: testTelemetryObject.identifier
+                }
+            ];
+            overlayPlotObject.configuration.series = [
+                {
+                    identifier: testTelemetryObject.identifier
+                }
+            ];
+            mockComposition = new EventEmitter();
+            mockComposition.load = () => {
+                mockComposition.emit('add', testTelemetryObject);
+
+                return [testTelemetryObject];
+            };
+
+            spyOn(openmct.composition, 'get').and.returnValue(mockComposition);
+
+            let viewContainer = document.createElement("div");
+            child.append(viewContainer);
+            component = new Vue({
+                el: viewContainer,
+                components: {
+                    Plot
+                },
+                provide: {
+                    openmct: openmct,
+                    domainObject: overlayPlotObject,
+                    composition: openmct.composition.get(overlayPlotObject),
+                    path: [overlayPlotObject]
+                },
+                template: '<plot ref="plotComponent"></plot>'
+            });
+
+            return telemetryPromise
+                .then(Vue.nextTick())
+                .then(() => {
+                    const configId = openmct.objects.makeKeyString(overlayPlotObject.identifier);
+                    config = configStore.get(configId);
+                });
+        });
+
+        it("Renders single Y-axis for the telemetry object", (done) => {
+            config.yAxis.set('displayRange', {
+                min: 10,
+                max: 20
+            });
+            Vue.nextTick(() => {
+                let yAxisElement = element.querySelectorAll(".gl-plot-axis-area.gl-plot-y .gl-plot-tick-wrapper");
+                expect(yAxisElement.length).toBe(1);
+                done();
+            });
+        });
+    });
+});

src/plugins/plot/pluginSpec.js

@@ -28,6 +28,8 @@ import EventEmitter from "EventEmitter";
 import PlotOptions from "./inspector/PlotOptions.vue";
 import PlotConfigurationModel from "./configuration/PlotConfigurationModel";
 
+const TEST_KEY_ID = 'test-key';
+
 describe("the plugin", function () {
     let element;
     let child;
@@ -404,6 +406,20 @@ describe("the plugin", function () {
             expect(options[1].value).toBe("Another attribute");
         });
 
+        it("Updates the Y-axis label when changed", () => {
+            const configId = openmct.objects.makeKeyString(testTelemetryObject.identifier);
+            const config = configStore.get(configId);
+            const yAxisElement = element.querySelectorAll(".gl-plot-axis-area.gl-plot-y")[0].__vue__;
+            config.yAxis.seriesCollection.models.forEach((plotSeries) => {
+                expect(plotSeries.model.yKey).toBe('some-key');
+            });
+
+            yAxisElement.$emit('yKeyChanged', TEST_KEY_ID, 1);
+            config.yAxis.seriesCollection.models.forEach((plotSeries) => {
+                expect(plotSeries.model.yKey).toBe(TEST_KEY_ID);
+            });
+        });
+
         it('hides the pause and play controls', () => {
             let pauseEl = element.querySelectorAll(".c-button-set .icon-pause");
             let playEl = element.querySelectorAll(".c-button-set .icon-arrow-right");

src/styles/_legacy-plots.scss

@@ -593,6 +593,8 @@ mct-plot {
 .plot-legend-left .gl-plot-legend { margin-right: $interiorMargin; }
 .plot-legend-right .gl-plot-legend { margin-left: $interiorMargin; }
 
+.gl-plot .plot-yaxis-right.gl-plot-y { margin-left: 100%; }
+
 .gl-plot,
 .c-plot {
     &.plot-legend-collapsed .plot-wrapper-expanded-legend { display: none; }

src/ui/inspector/ElementItem.vue

@@ -25,7 +25,7 @@
     draggable="true"
     @dragstart="emitDragStartEvent"
     @dragenter="onDragenter"
-    @dragover="onDragover"
+    @dragover.prevent
     @dragleave="onDragleave"
     @drop="emitDropEvent"
 >
@@ -38,6 +38,7 @@
         }"
     >
         <span
+            v-if="showGrippy"
             class="c-elements-pool__grippy c-grippy c-grippy--vertical-drag"
         ></span>
         <object-label
@@ -81,6 +82,10 @@ export default {
         },
         allowDrop: {
             type: Boolean
+        },
+        showGrippy: {
+            type: Boolean,
+            default: true
         }
     },
     data() {
@@ -93,11 +98,8 @@ export default {
         };
     },
     methods: {
-        onDragover(event) {
-            event.preventDefault();
-        },
         emitDropEvent(event) {
-            this.$emit('drop-custom', this.index);
+            this.$emit('drop-custom', event);
             this.hover = false;
         },
         emitDragStartEvent(event) {

src/ui/inspector/ElementItemGroup.vue

@@ -0,0 +1,101 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2022, 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.
+ *****************************************************************************/
+
+<template>
+<div
+    class="c-elements-pool__group"
+    :class="{
+        'hover': hover
+    }"
+    :allow-drop="allowDrop"
+    @dragover.prevent
+    @dragenter="onDragEnter"
+    @dragleave.stop="onDragLeave"
+    @drop="emitDrop"
+>
+    <ul>
+        <div>
+            <span class="c-elements-pool__grippy c-grippy c-grippy--vertical-drag"></span>
+            <div
+                class="c-tree__item__type-icon c-object-label__type-icon"
+            >
+                <span
+                    class="is-status__indicator"
+                ></span>
+            </div>
+            <div
+                class="c-tree__item__name c-object-label__name"
+                aria-label="Element Item Group"
+            >
+                {{ label }}
+            </div>
+        </div>
+        <slot></slot>
+    </ul>
+</div>
+</template>
+
+<script>
+export default {
+    props: {
+        parentObject: {
+            type: Object,
+            required: true,
+            default: () => {
+                return {};
+            }
+        },
+        label: {
+            type: String,
+            required: true,
+            default: () => {
+                return '';
+            }
+        },
+        allowDrop: {
+            type: Boolean
+        }
+    },
+    data() {
+        return {
+            dragCounter: 0
+        };
+    },
+    computed: {
+        hover() {
+            return this.dragCounter > 0;
+        }
+    },
+    methods: {
+        emitDrop(event) {
+            this.dragCounter = 0;
+            this.$emit('drop-group', event);
+        },
+        onDragEnter(event) {
+            this.dragCounter++;
+        },
+        onDragLeave(event) {
+            this.dragCounter--;
+        }
+    }
+};
+</script>

src/ui/inspector/ElementsPool.vue

@@ -65,8 +65,8 @@ import ElementItem from './ElementItem.vue';
 
 export default {
     components: {
-        'Search': Search,
-        'ElementItem': ElementItem
+        Search,
+        ElementItem
     },
     inject: ['openmct'],
     data() {

src/ui/inspector/Inspector.vue

@@ -56,7 +56,12 @@
                 handle="before"
                 label="Elements"
             >
-                <elements-pool />
+                <plot-elements-pool
+                    v-if="isOverlayPlot"
+                />
+                <elements-pool
+                    v-else
+                />
             </pane>
         </multipane>
         <multipane
@@ -83,6 +88,7 @@
 import multipane from '../layout/multipane.vue';
 import pane from '../layout/pane.vue';
 import ElementsPool from './ElementsPool.vue';
+import PlotElementsPool from './PlotElementsPool.vue';
 import Location from './Location.vue';
 import Properties from './details/Properties.vue';
 import ObjectName from './ObjectName.vue';
@@ -99,6 +105,7 @@ export default {
         multipane,
         pane,
         ElementsPool,
+        PlotElementsPool,
         Properties,
         ObjectName,
         Location,
@@ -118,6 +125,7 @@ export default {
         return {
             hasComposition: false,
             showStyles: false,
+            isOverlayPlot: false,
             tabbedViews: [{
                 key: '__properties',
                 name: 'Properties'
@@ -151,6 +159,7 @@ export default {
                 let parentObject = selection[0][0].context.item;
 
                 this.hasComposition = Boolean(parentObject && this.openmct.composition.get(parentObject));
+                this.isOverlayPlot = selection[0][0].context.item.type === 'telemetry.plot.overlay';
             }
         },
         refreshTabs(selection) {

src/ui/inspector/PlotElementsPool.vue

@@ -0,0 +1,330 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2022, 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.
+ *****************************************************************************/
+
+<template>
+<div class="c-elements-pool">
+    <Search
+        class="c-elements-pool__search"
+        :value="currentSearch"
+        @input="applySearch"
+        @clear="applySearch"
+    />
+    <div
+        class="c-elements-pool__elements"
+    >
+        <ul
+            v-if="hasElements"
+            id="inspector-elements-tree"
+            class="c-tree c-elements-pool__tree"
+        >
+            <element-item-group
+                v-for="(yAxis, index) in yAxes"
+                :key="`element-group-yaxis-${yAxis.id}`"
+                :parent-object="parentObject"
+                :allow-drop="allowDrop"
+                :label="`Y Axis ${yAxis.id}`"
+                @drop-group="moveTo($event, 0, yAxis.id)"
+            >
+                <li
+                    class="js-first-place"
+                    @drop="moveTo($event, 0, yAxis.id)"
+                ></li>
+                <element-item
+                    v-for="(element, elemIndex) in yAxis.elements"
+                    :key="element.identifier.key"
+                    :index="elemIndex"
+                    :element-object="element"
+                    :parent-object="parentObject"
+                    :allow-drop="allowDrop"
+                    :show-grippy="false"
+                    @dragstart-custom="moveFrom($event, yAxis.id)"
+                    @drop-custom="moveTo($event, index, yAxis.id)"
+                />
+                <li
+                    v-if="yAxis.elements.length > 0"
+                    class="js-last-place"
+                    @drop="moveTo($event, yAxis.elements.length, yAxis.id)"
+                ></li>
+            </element-item-group>
+        </ul>
+        <div
+            v-if="!hasElements"
+        >
+            No contained elements
+        </div>
+    </div>
+</div>
+</template>
+
+<script>
+import _ from 'lodash';
+import Search from '../components/search.vue';
+import ElementItem from './ElementItem.vue';
+import ElementItemGroup from './ElementItemGroup.vue';
+import configStore from '../../plugins/plot/configuration/ConfigStore';
+
+const Y_AXIS_1 = 1;
+
+export default {
+    components: {
+        Search,
+        ElementItemGroup,
+        ElementItem
+    },
+    inject: ['openmct'],
+    data() {
+        return {
+            yAxes: [],
+            isEditing: this.openmct.editor.isEditing(),
+            parentObject: undefined,
+            currentSearch: '',
+            selection: [],
+            contextClickTracker: {},
+            allowDrop: false
+        };
+    },
+    computed: {
+        hasElements() {
+            for (const yAxis of this.yAxes) {
+                if (yAxis.elements.length > 0) {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+    },
+    mounted() {
+        const selection = this.openmct.selection.get();
+        if (selection && selection.length > 0) {
+            this.showSelection(selection);
+        }
+
+        this.openmct.selection.on('change', this.showSelection);
+        this.openmct.editor.on('isEditing', this.setEditState);
+    },
+    destroyed() {
+        this.openmct.editor.off('isEditing', this.setEditState);
+        this.openmct.selection.off('change', this.showSelection);
+
+        this.unlistenComposition();
+    },
+    methods: {
+        setEditState(isEditing) {
+            this.isEditing = isEditing;
+            this.showSelection(this.openmct.selection.get());
+        },
+        showSelection(selection) {
+            if (_.isEqual(this.selection, selection)) {
+                return;
+            }
+
+            this.selection = selection;
+            this.elementsCache = {};
+            this.listeners = [];
+            this.parentObject = selection && selection[0] && selection[0][0].context.item;
+
+            this.unlistenComposition();
+
+            if (this.parentObject) {
+                this.setYAxisIds();
+                this.composition = this.openmct.composition.get(this.parentObject);
+
+                if (this.composition) {
+                    this.composition.load();
+                    this.registerCompositionListeners();
+                }
+            }
+        },
+        unlistenComposition() {
+            if (this.compositionUnlistener) {
+                this.compositionUnlistener();
+            }
+        },
+        registerCompositionListeners() {
+            this.composition.on('add', this.addElement);
+            this.composition.on('remove', this.removeElement);
+            this.composition.on('reorder', this.reorderElements);
+
+            this.compositionUnlistener = () => {
+                this.composition.off('add', this.addElement);
+                this.composition.off('remove', this.removeElement);
+                this.composition.off('reorder', this.reorderElements);
+                delete this.compositionUnlistener;
+            };
+        },
+        setYAxisIds() {
+            const configId = this.openmct.objects.makeKeyString(this.parentObject.identifier);
+            this.config = configStore.get(configId);
+            this.yAxes.push({
+                id: this.config.yAxis.id,
+                elements: this.parentObject.configuration.series.filter(
+                    series => series.yAxisId === this.config.yAxis.id
+                )
+            });
+            if (this.config.additionalYAxes) {
+                this.config.additionalYAxes.forEach(yAxis => {
+                    this.yAxes.push({
+                        id: yAxis.id,
+                        elements: this.parentObject.configuration.series.filter(
+                            series => series.yAxisId === yAxis.id
+                        )
+                    });
+                });
+            }
+        },
+        addElement(element) {
+            // Get the index of the corresponding element in the series list
+            const seriesIndex = this.parentObject.configuration.series.findIndex(
+                series => this.openmct.objects.areIdsEqual(series.identifier, element.identifier)
+            );
+            const keyString = this.openmct.objects.makeKeyString(element.identifier);
+
+            const wasDraggedOntoPlot = this.parentObject.configuration.series[seriesIndex].yAxisId === undefined;
+            const yAxisId = wasDraggedOntoPlot
+                ? Y_AXIS_1
+                : this.parentObject.configuration.series[seriesIndex].yAxisId;
+
+            if (wasDraggedOntoPlot) {
+                const insertIndex = this.yAxes[0].elements.length;
+                // Insert the element at the end of the first YAxis bucket
+                this.composition.reorder(seriesIndex, insertIndex);
+            }
+
+            // Store the element in the cache and set its yAxisId
+            this.elementsCache[keyString] = JSON.parse(JSON.stringify(element));
+            if (this.elementsCache[keyString].yAxisId !== yAxisId) {
+                // Mutate the YAxisId on the domainObject itself
+                this.updateCacheAndMutate(element, yAxisId);
+            }
+
+            this.applySearch(this.currentSearch);
+        },
+        reorderElements() {
+            this.applySearch(this.currentSearch);
+        },
+        removeElement(identifier) {
+            const keyString = this.openmct.objects.makeKeyString(identifier);
+            delete this.elementsCache[keyString];
+            this.applySearch(this.currentSearch);
+        },
+        applySearch(input) {
+            this.currentSearch = input;
+            this.yAxes.forEach(yAxis => {
+                yAxis.elements = this.filterForSearchAndAxis(input, yAxis.id);
+            });
+        },
+        filterForSearchAndAxis(input, yAxisId) {
+            return this.parentObject.composition.map((id) =>
+                this.elementsCache[this.openmct.objects.makeKeyString(id)]
+            ).filter((element) => {
+                return element !== undefined
+                    && element.name.toLowerCase().search(input) !== -1
+                    && element.yAxisId === yAxisId;
+            });
+        },
+        moveFrom(elementIndex, groupIndex) {
+            this.allowDrop = true;
+            this.moveFromIndex = elementIndex;
+            this.moveFromYAxisId = groupIndex;
+        },
+        moveTo(event, moveToIndex, moveToYAxisId) {
+            // FIXME: If the user starts the drag by clicking outside of the <object-label/> element,
+            // domain object information will not be set on the dataTransfer data. To prevent errors,
+            // we simply short-circuit here if the data is not set.
+            const serializedDomainObject = event.dataTransfer.getData('openmct/composable-domain-object');
+            if (!serializedDomainObject) {
+                return;
+            }
+
+            const domainObject = JSON.parse(serializedDomainObject);
+            this.updateCacheAndMutate(domainObject, moveToYAxisId);
+
+            const moveFromIndex = this.moveFromIndex;
+
+            this.moveAndReorderElement(moveFromIndex, moveToIndex, moveToYAxisId);
+        },
+        updateCacheAndMutate(domainObject, yAxisId) {
+            const keyString = this.openmct.objects.makeKeyString(domainObject.identifier);
+            const index = this.parentObject.configuration.series.findIndex(
+                series => series.identifier.key === domainObject.identifier.key
+            );
+
+            // Handle the case of dragging an element directly into the Elements Pool
+            if (!this.elementsCache[keyString]) {
+                // Update the series list locally so our CompositionAdd handler can
+                // take care of the rest.
+                this.parentObject.configuration.series.push({
+                    identifier: domainObject.identifier,
+                    yAxisId
+                });
+                this.composition.add(domainObject);
+                this.elementsCache[keyString] = JSON.parse(JSON.stringify(domainObject));
+            }
+
+            this.elementsCache[keyString].yAxisId = yAxisId;
+            const shouldMutate = this.parentObject.configuration.series?.[index]?.yAxisId !== yAxisId;
+            if (shouldMutate) {
+                this.openmct.objects.mutate(
+                    this.parentObject,
+                    `configuration.series[${index}].yAxisId`,
+                    yAxisId
+                );
+            }
+        },
+        moveAndReorderElement(moveFromIndex, moveToIndex, moveToYAxisId) {
+            if (!this.allowDrop) {
+                return;
+            }
+
+            // Find the corresponding indexes of the from/to yAxes in the yAxes list
+            const moveFromYAxisIndex = this.yAxes.findIndex(yAxis => yAxis.id === this.moveFromYAxisId);
+            const moveToYAxisIndex = this.yAxes.findIndex(yAxis => yAxis.id === moveToYAxisId);
+
+            // Calculate the actual indexes of the elements in the composition array
+            // based on which bucket and index they are being moved from/to.
+            // Then, trigger a composition reorder.
+            for (let yAxisId = 0; yAxisId < moveFromYAxisIndex; yAxisId++) {
+                const lesserYAxisBucketLength = this.yAxes[yAxisId].elements.length;
+                // Add the lengths of preceding buckets to calculate the actual 'from' index
+                moveFromIndex = moveFromIndex + lesserYAxisBucketLength;
+            }
+
+            for (let yAxisId = 0; yAxisId < moveToYAxisIndex; yAxisId++) {
+                const greaterYAxisBucketLength = this.yAxes[yAxisId].elements.length;
+                // Add the lengths of subsequent buckets to calculate the actual 'to' index
+                moveToIndex = moveToIndex + greaterYAxisBucketLength;
+            }
+
+            // Adjust the index by 1 if we're moving from one bucket to another
+            if (this.moveFromYAxisId !== moveToYAxisId && moveToIndex > 0) {
+                moveToIndex--;
+            }
+
+            // Reorder the composition array according to the calculated indexes
+            this.composition.reorder(moveFromIndex, moveToIndex);
+
+            this.allowDrop = false;
+        }
+    }
+};
+</script>

src/ui/inspector/elements.scss

@@ -21,6 +21,11 @@
         flex: 0 0 auto;
     }
 
+    &__group {
+        flex: 1 1 auto;
+        overflow: auto;
+    }
+
     &__elements {
         flex: 1 1 auto;
         overflow: auto;