add an initial manually-created visual snapshot test of log plot chart

This almost works: ticks don't redraw until a zoom or pan is performed.

e2e/tests/plugins/plot/log-plot.e2e.spec.js

@@ -0,0 +1,279 @@
+/*****************************************************************************
+ * 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.
+*/
+
+const { test, expect } = require('@playwright/test');
+
+test.describe('Log plot tests', () => {
+    test.only('Can create a log plot.', async ({ page }) => {
+        await makeOverlayPlot(page);
+        await testRegularTicks(page);
+        await enableEditMode(page);
+        await enableLogMode(page);
+        await testLogTicks(page);
+        await disableLogMode(page);
+        await testRegularTicks(page);
+        await enableLogMode(page);
+        await testLogTicks(page);
+        await saveOverlayPlot(page);
+        await testLogTicks(page);
+        await testLogPlotPixels(page);
+
+        // refresh page
+        await page.reload();
+
+        // test log ticks hold up after refresh
+        await testLogTicks(page);
+        await testLogPlotPixels(page);
+    });
+
+    test.only('Verify that log mode option is reflected in import/export JSON', async ({ page }) => {
+        await makeOverlayPlot(page);
+        await enableEditMode(page);
+        await enableLogMode(page);
+        await saveOverlayPlot(page);
+
+        // TODO ...export, delete the overlay, then import it...
+
+        await testLogTicks(page);
+
+        // TODO, the plot is slightly at different position that in the other test, so this fails.
+        // ...We can fix it by copying all steps from the first test...
+        // await testLogPlotPixels(page);
+    });
+});
+
+/**
+ * Makes an overlay plot with a sine wave generator and clicks on the overlay plot in the sidebar so it is the active thing displayed.
+ * @param {import('@playwright/test').Page} page
+ */
+async function makeOverlayPlot(page) {
+    // fresh page with time range from 2022-03-29 22:00:00.000Z to 2022-03-29 22:00:30.000Z
+    await page.goto('/', { waitUntil: 'networkidle' });
+
+    // Set a specific time range for consistency, otherwise it will change
+    // on every test to a range based on the current time.
+
+    const timeInputs = page.locator('input.c-input--datetime');
+    await timeInputs.first().click();
+    await timeInputs.first().fill('2022-03-29 22:00:00.000Z');
+
+    await timeInputs.nth(1).click();
+    await timeInputs.nth(1).fill('2022-03-29 22:00:30.000Z');
+
+    // create overlay plot
+
+    await page.locator('button.c-create-button').click();
+    await page.locator('li:has-text("Overlay Plot")').click();
+    await Promise.all([
+        page.waitForNavigation(/*{ url: 'http://localhost:8080/#/browse/mine/8caf7072-535b-4af6-8394-edd86e3ea35f?tc.mode=fixed&tc.startBound=1648590633191&tc.endBound=1648592433191&tc.timeSystem=utc&view=plot-overlay' }*/),
+        page.locator('text=OK').click()
+    ]);
+
+    // save the overlay plot
+
+    await page.locator('text=Snapshot Save and Finish Editing Save and Continue Editing >> button').nth(1).click();
+    await page.locator('text=Save and Finish Editing').click();
+
+    // create a sinewave generator
+
+    await page.locator('button.c-create-button').click();
+    await page.locator('li:has-text("Sine Wave Generator")').click();
+
+    // set amplitude to 6, offset 4, period 2
+
+    await page.locator('div:nth-child(5) .form-row .c-form-row__controls .form-control .field input').click();
+    await page.locator('div:nth-child(5) .form-row .c-form-row__controls .form-control .field input').fill('6');
+
+    await page.locator('div:nth-child(6) .form-row .c-form-row__controls .form-control .field input').click();
+    await page.locator('div:nth-child(6) .form-row .c-form-row__controls .form-control .field input').fill('4');
+
+    await page.locator('div:nth-child(7) .form-row .c-form-row__controls .form-control .field input').click();
+    await page.locator('div:nth-child(7) .form-row .c-form-row__controls .form-control .field input').fill('2');
+
+    // Click OK to make generator
+
+    await Promise.all([
+        page.waitForNavigation(/*{ url: 'http://localhost:8080/#/browse/mine/8caf7072-535b-4af6-8394-edd86e3ea35f/6e58b26a-8a73-4df6-b3a6-918decc0bbfa?tc.mode=fixed&tc.startBound=1648590633191&tc.endBound=1648592433191&tc.timeSystem=utc&view=plot-single' }*/),
+        page.locator('text=OK').click()
+    ]);
+
+    // click on overlay plot
+
+    await page.locator('text=Open MCT My Items >> span').nth(3).click();
+    await Promise.all([
+        page.waitForNavigation(/*{ url: 'http://localhost:8080/#/browse/mine/8caf7072-535b-4af6-8394-edd86e3ea35f?tc.mode=fixed&tc.startBound=1648590633191&tc.endBound=1648592433191&tc.timeSystem=utc&view=plot-overlay' }*/),
+        page.locator('text=Unnamed Overlay Plot').first().click()
+    ]);
+}
+
+/**
+ * @param {import('@playwright/test').Page} page
+ */
+async function testRegularTicks(page) {
+    const yTicks = page.locator('.gl-plot-y-tick-label');
+    expect(await yTicks.count()).toBe(7);
+    await expect(yTicks.nth(0)).toHaveText('-2');
+    await expect(yTicks.nth(1)).toHaveText('0');
+    await expect(yTicks.nth(2)).toHaveText('2');
+    await expect(yTicks.nth(3)).toHaveText('4');
+    await expect(yTicks.nth(4)).toHaveText('6');
+    await expect(yTicks.nth(5)).toHaveText('8');
+    await expect(yTicks.nth(6)).toHaveText('10');
+}
+
+/**
+ * @param {import('@playwright/test').Page} page
+ */
+async function testLogTicks(page) {
+    const yTicks = page.locator('.gl-plot-y-tick-label');
+    expect(await yTicks.count()).toBe(28);
+    await expect(yTicks.nth(0)).toHaveText('-2.98');
+    await expect(yTicks.nth(1)).toHaveText('-2.50');
+    await expect(yTicks.nth(2)).toHaveText('-2.00');
+    await expect(yTicks.nth(3)).toHaveText('-1.51');
+    await expect(yTicks.nth(4)).toHaveText('-1.20');
+    await expect(yTicks.nth(5)).toHaveText('-1.00');
+    await expect(yTicks.nth(6)).toHaveText('-0.80');
+    await expect(yTicks.nth(7)).toHaveText('-0.58');
+    await expect(yTicks.nth(8)).toHaveText('-0.40');
+    await expect(yTicks.nth(9)).toHaveText('-0.20');
+    await expect(yTicks.nth(10)).toHaveText('-0.00');
+    await expect(yTicks.nth(11)).toHaveText('0.20');
+    await expect(yTicks.nth(12)).toHaveText('0.40');
+    await expect(yTicks.nth(13)).toHaveText('0.58');
+    await expect(yTicks.nth(14)).toHaveText('0.80');
+    await expect(yTicks.nth(15)).toHaveText('1.00');
+    await expect(yTicks.nth(16)).toHaveText('1.20');
+    await expect(yTicks.nth(17)).toHaveText('1.51');
+    await expect(yTicks.nth(18)).toHaveText('2.00');
+    await expect(yTicks.nth(19)).toHaveText('2.50');
+    await expect(yTicks.nth(20)).toHaveText('2.98');
+    await expect(yTicks.nth(21)).toHaveText('3.50');
+    await expect(yTicks.nth(22)).toHaveText('4.00');
+    await expect(yTicks.nth(23)).toHaveText('4.50');
+    await expect(yTicks.nth(24)).toHaveText('5.31');
+    await expect(yTicks.nth(25)).toHaveText('7.00');
+    await expect(yTicks.nth(26)).toHaveText('8.00');
+    await expect(yTicks.nth(27)).toHaveText('9.00');
+}
+
+/**
+ * @param {import('@playwright/test').Page} page
+ */
+async function enableEditMode(page) {
+    // turn on edit mode
+    await page.locator('text=Unnamed Overlay Plot Snapshot >> button').nth(3).click();
+}
+
+/**
+ * @param {import('@playwright/test').Page} 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();
+}
+
+/**
+ * @param {import('@playwright/test').Page} 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();
+}
+
+/**
+ * @param {import('@playwright/test').Page} page
+ */
+async function saveOverlayPlot(page) {
+    // save overlay plot
+    await page.locator('text=Snapshot Save and Finish Editing Save and Continue Editing >> button').nth(1).click();
+    await page.locator('text=Save and Finish Editing').click();
+}
+
+/**
+ * @param {import('@playwright/test').Page} page
+ */
+async function testLogPlotPixels(page) {
+    const pixelsMatch = await page.evaluate(async () => {
+        // TODO get canvas pixels at a few locations to make sure they're the correct color, to test that the plot comes out as expected.
+
+        await new Promise((r) => setTimeout(r, 50));
+
+        // These are some pixels that should be blue points in the log plot.
+        // If the plot changes shape to an unexpected shape, this will
+        // likely fail, which is what we want.
+        //
+        // I found these pixels by pausing playwright in debug mode at this
+        // point, and using similar code as below to output the pixel data, then
+        // I logged those pixels here.
+        const expectedBluePixels = [
+            // TODO these pixel sets only work with the first test, but not the second test.
+
+            // [60, 35],
+            // [121, 125],
+            // [156, 377],
+            // [264, 73],
+            // [372, 186],
+            // [576, 73],
+            // [659, 439],
+            // [675, 423]
+
+            [60, 35],
+            [120, 125],
+            [156, 375],
+            [264, 73],
+            [372, 185],
+            [575, 72],
+            [659, 437],
+            [675, 421]
+        ];
+
+        // The first canvas in the DOM is the one that has the plot point
+        // icons (canvas 2d), which is the one we are testing. The second
+        // one in the DOM is the WebGL canvas with the line. (Why aren't
+        // they both WebGL?)
+        const canvas = document.querySelector('canvas');
+
+        const ctx = canvas.getContext('2d');
+
+        for (const pixel of expectedBluePixels) {
+            // XXX Possible optimization: call getImageData only once with
+            // area including all pixels to be tested.
+            const data = ctx.getImageData(pixel[0], pixel[1], 1, 1).data;
+
+            // #43b0ffff <-- openmct cyanish-blue with 100% opacity
+            // if (data[0] !== 0x43 || data[1] !== 0xb0 || data[2] !== 0xff || data[3] !== 0xff) {
+            if (data[0] === 0 && data[1] === 0 && data[2] === 0 && data[3] === 0) {
+                // If any pixel is empty, it means we didn't hit a plot point.
+                return false;
+            }
+        }
+
+        return true;
+    });
+
+    expect(pixelsMatch).toBe(true);
+}

package.json

@@ -95,6 +95,7 @@
     "test:debug": "cross-env NODE_ENV=debug karma start --no-single-run",
     "test:e2e:ci": "npx playwright test --config=e2e/playwright-ci.config.js --project=chrome smoke default condition timeConductor",
     "test:e2e:local": "npx playwright test --config=e2e/playwright-local.config.js --project=chrome",
+    "test:e2e:debug": "npm run test:e2e:local -- --debug",
     "test:e2e:visual": "percy exec --config ./e2e/.percy.yml -- npx playwright test --config=e2e/playwright-visual.config.js default",
     "test:e2e:full": "npx playwright test --config=e2e/playwright-ci.config.js",
     "test:watch": "cross-env NODE_OPTIONS=\"--max_old_space_size=4096\" karma start --no-single-run",

src/plugins/plot/MctTicks.vue

@@ -30,8 +30,8 @@
         class="gl-plot-tick-wrapper"
     >
         <div
-            v-for="tick in ticks"
-            :key="tick.value"
+            v-for="(tick, i) in ticks"
+            :key="i"
             class="gl-plot-tick gl-plot-x-tick-label"
             :style="{
                 left: (100 * (tick.value - min) / interval) + '%'
@@ -46,8 +46,8 @@
         class="gl-plot-tick-wrapper"
     >
         <div
-            v-for="tick in ticks"
-            :key="tick.value"
+            v-for="(tick, i) in ticks"
+            :key="i"
             class="gl-plot-tick gl-plot-y-tick-label"
             :style="{ top: (100 * (max - tick.value) / interval) + '%' }"
             :title="tick.fullText || tick.text"
@@ -59,8 +59,8 @@
     <!-- grid lines follow -->
     <template v-if="position === 'right'">
         <div
-            v-for="tick in ticks"
-            :key="tick.value"
+            v-for="(tick, i) in ticks"
+            :key="i"
             class="gl-plot-hash hash-v"
             :style="{
                 right: (100 * (max - tick.value) / interval) + '%',
@@ -71,8 +71,8 @@
     </template>
     <template v-if="position === 'bottom'">
         <div
-            v-for="tick in ticks"
-            :key="tick.value"
+            v-for="(tick, i) in ticks"
+            :key="i"
             class="gl-plot-hash hash-h"
             :style="{ bottom: (100 * (tick.value - min) / interval) + '%', width: '100%' }"
         >
@@ -83,7 +83,7 @@
 
 <script>
 import eventHelpers from "./lib/eventHelpers";
-import { ticks, getFormattedTicks } from "./tickUtils";
+import { ticks, getLogTicks, getFormattedTicks } from "./tickUtils";
 import configStore from "./configuration/ConfigStore";
 
 export default {
@@ -96,6 +96,13 @@ export default {
             },
             required: true
         },
+        // Make it a prop, then later we can allow user to change it via UI input
+        tickCount: {
+            type: Number,
+            default() {
+                return 6;
+            }
+        },
         position: {
             required: true,
             type: String,
@@ -118,7 +125,6 @@ export default {
 
         this.axis = this.getAxisFromConfig();
 
-        this.tickCount = 4;
         this.tickUpdate = false;
         this.listenTo(this.axis, 'change:displayRange', this.updateTicks, this);
         this.listenTo(this.axis, 'change:format', this.updateTicks, this);
@@ -184,7 +190,12 @@ export default {
                 }, this);
             }
 
-            return ticks(range.min, range.max, number);
+            if (this.axisType === 'yAxis' && this.axis.get('logMode')) {
+                return getLogTicks(range.min, range.max, number, 4);
+                // return getLogTicks2(range.min, range.max, number);
+            } else {
+                return ticks(range.min, range.max, number);
+            }
         },
 
         updateTicksForceRegeneration() {

src/plugins/plot/chart/MCTChartLineStepAfter.js

@@ -23,7 +23,7 @@
 import MCTChartSeriesElement from './MCTChartSeriesElement';
 
 export default class MCTChartLineStepAfter extends MCTChartSeriesElement {
-    removePoint(point, index, count) {
+    removePoint(index) {
         if (index > 0 && index / 2 < this.count) {
             this.buffer[index + 1] = this.buffer[index - 1];
         }

src/plugins/plot/chart/MCTChartSeriesElement.js

@@ -85,11 +85,10 @@ export default class MCTChartSeriesElement {
 
         this.removeSegments(removalPoint, vertexCount);
 
-        this.removePoint(
-            this.makePoint(point, series),
-            removalPoint,
-            vertexCount
-        );
+        // TODO useless makePoint call?
+        this.makePoint(point, series);
+        this.removePoint(removalPoint);
+
         this.count -= (vertexCount / 2);
     }
 
@@ -109,11 +108,7 @@ export default class MCTChartSeriesElement {
         const insertionPoint = this.startIndexForPointAtIndex(index);
         this.growIfNeeded(pointsRequired);
         this.makeInsertionPoint(insertionPoint, pointsRequired);
-        this.addPoint(
-            this.makePoint(point, series),
-            insertionPoint,
-            pointsRequired
-        );
+        this.addPoint(this.makePoint(point, series), insertionPoint);
         this.count += (pointsRequired / 2);
     }
 

src/plugins/plot/chart/MctChart.vue

@@ -279,7 +279,7 @@ export default {
             // Have to throw away the old canvas elements and replace with new
             // canvas elements in order to get new drawing contexts.
             const div = document.createElement('div');
-            div.innerHTML = this.canvasTemplate + this.canvasTemplate;
+            div.innerHTML = this.TEMPLATE;
             const mainCanvas = div.querySelectorAll("canvas")[1];
             const overlayCanvas = div.querySelectorAll("canvas")[0];
             this.canvas.parentNode.replaceChild(mainCanvas, this.canvas);

src/plugins/plot/configuration/Model.js

@@ -71,6 +71,7 @@ export default class Model extends EventEmitter {
     }
 
     /**
+     * @abstract
      * @param {ModelOptions<T, O>} options
      */
     initialize(options) {

src/plugins/plot/configuration/PlotSeries.js

@@ -23,6 +23,7 @@ import _ from 'lodash';
 import Model from "./Model";
 import { MARKER_SHAPES } from '../draw/MarkerShapes';
 import configStore from "../configuration/ConfigStore";
+import { symlog } from '../mathUtils';
 
 /**
  * Plot series handle interpreting telemetry metadata for a single telemetry
@@ -63,6 +64,8 @@ import configStore from "../configuration/ConfigStore";
  * @extends {Model<PlotSeriesModelType, PlotSeriesModelOptions>}
  */
 export default class PlotSeries extends Model {
+    logMode = false;
+
     /**
      @param {import('./Model').ModelOptions<PlotSeriesModelType, PlotSeriesModelOptions>} options
      */
@@ -70,6 +73,8 @@ export default class PlotSeries extends Model {
 
         super(options);
 
+        this.logMode = options.collection.plot.model.yAxis.logMode;
+
         this.listenTo(this, 'change:xKey', this.onXKeyChange, this);
         this.listenTo(this, 'change:yKey', this.onYKeyChange, this);
         this.persistedConfig = options.persistedConfig;
@@ -229,6 +234,7 @@ export default class PlotSeries extends Model {
             this.getXVal = format.parse.bind(format);
         }
     }
+
     /**
      * Update y formatter on change, default to stepAfter interpolation if
      * y range is an enumeration.
@@ -251,7 +257,12 @@ export default class PlotSeries extends Model {
             return this.limitEvaluator.evaluate(datum, valueMetadata);
         }.bind(this);
         const format = this.formats[newKey];
-        this.getYVal = format.parse.bind(format);
+        this.getYVal = (value) => {
+            const scale = 1; // TODO get from UI, positive number above 0
+            const y = format.parse(value);
+
+            return this.logMode ? scale * symlog(y, 10) : y;
+        };
     }
 
     formatX(point) {
@@ -519,7 +530,8 @@ export default class PlotSeries extends Model {
 
     /**
      * Update the series data with the given value.
-     * @returns {Array<{
+     * This return type definition is totally wrong, only covers sinwave generator. It needs to be generic.
+     * @return-example {Array<{
             cos: number
             sin: number
             mctLimitState: {

src/plugins/plot/configuration/YAxisModel.js

@@ -19,7 +19,7 @@
  * this source code distribution or the Licensing information page available
  * at runtime from the About dialog for additional information.
  *****************************************************************************/
-import _ from 'lodash';
+import { antisymlog, symlog } from '../mathUtils';
 import Model from './Model';
 
 /**
@@ -31,7 +31,7 @@ import Model from './Model';
  *
  * `autoscale`: boolean, whether or not to autoscale.
  * `autoscalePadding`: float, percent of padding to display in plots.
- * `displayRange`: the current display range for the x Axis.
+ * `displayRange`: the current display range for the axis.
  * `format`: the formatter for the axis.
  * `frozen`: boolean, if true, displayRange will not be updated automatically.
  *           Used to temporarily disable automatic updates during user interaction.
@@ -54,6 +54,7 @@ export default class YAxisModel extends Model {
         this.listenTo(this, 'change:stats', this.calculateAutoscaleExtents, this);
         this.listenTo(this, 'change:autoscale', this.toggleAutoscale, this);
         this.listenTo(this, 'change:autoscalePadding', this.updatePadding, this);
+        this.listenTo(this, 'change:logMode', this.onLogModeChange, this);
         this.listenTo(this, 'change:frozen', this.toggleFreeze, this);
         this.listenTo(this, 'change:range', this.updateDisplayRange, this);
         this.updateDisplayRange(this.get('range'));
@@ -173,13 +174,38 @@ export default class YAxisModel extends Model {
             this.set('displayRange', this.get('range'));
         }
     }
+    /** @param {boolean} logMode */
+    onLogModeChange(logMode) {
+        const range = this.get('displayRange');
+        const scale = 1; // TODO get from UI, positive number above 0
+
+        if (logMode) {
+            range.min = scale * symlog(range.min, 10);
+            range.max = scale * symlog(range.max, 10);
+        } else {
+            range.min = antisymlog(range.min / scale, 10);
+            range.max = antisymlog(range.max / scale, 10);
+        }
+
+        this.set('displayRange', range);
+
+        this.resetSeries();
+    }
+    resetSeries() {
+        this.plot.series.forEach((plotSeries) => {
+            plotSeries.logMode = this.get('logMode');
+            plotSeries.reset(plotSeries.getSeriesData());
+        });
+        // Update the series collection labels and formatting
+        this.updateFromSeries(this.seriesCollection);
+    }
     /**
      * Update yAxis format, values, and label from known series.
      * @param {import('./SeriesCollection').default} seriesCollection
      */
     updateFromSeries(seriesCollection) {
         const plotModel = this.plot.get('domainObject');
-        const label = _.get(plotModel, 'configuration.yAxis.label');
+        const label = plotModel.configuration?.yAxis?.label;
         const sampleSeries = seriesCollection.first();
         if (!sampleSeries) {
             if (!label) {
@@ -192,7 +218,14 @@ export default class YAxisModel extends Model {
         const yKey = sampleSeries.get('yKey');
         const yMetadata = sampleSeries.metadata.value(yKey);
         const yFormat = sampleSeries.formats[yKey];
-        this.set('format', yFormat.format.bind(yFormat));
+        const scale = 1; // TODO get from UI, positive number above 0
+
+        if (this.get('logMode')) {
+            this.set('format', (n) => yFormat.format(antisymlog(n / scale, 10)));
+        } else {
+            this.set('format', (n) => yFormat.format(n));
+        }
+
         this.set('values', yMetadata.values);
         if (!label) {
             const labelName = seriesCollection.map(function (s) {
@@ -246,6 +279,7 @@ export default class YAxisModel extends Model {
         return {
             frozen: false,
             autoscale: true,
+            logMode: options.model?.logMode ?? false,
             autoscalePadding: 0.1
         };
     }
@@ -256,6 +290,7 @@ export default class YAxisModel extends Model {
 /**
 @typedef {import('./XAxisModel').AxisModelType & {
     autoscale: boolean
+    logMode: boolean
     autoscalePadding: number
     stats: import('./XAxisModel').NumberRange
     values: Array<TODO>

src/plugins/plot/inspector/PlotOptionsBrowse.vue

@@ -48,11 +48,19 @@
             <li class="grid-row">
                 <div
                     class="grid-cell label"
-                    title="Automatically scale the Y axis to keep all values in view."
-                >Autoscale</div>
+                    title="Enable log mode."
+                >Log mode</div>
                 <div class="grid-cell value">
-                    {{ autoscale ? "Enabled: " : "Disabled" }}
-                    {{ autoscale ? autoscalePadding : "" }}
+                    {{ logMode ? "Enabled" : "Disabled" }}
+                </div>
+            </li>
+            <li class="grid-row">
+                <div
+                    class="grid-cell label"
+                    title="Automatically scale the Y axis to keep all values in view."
+                >Auto scale</div>
+                <div class="grid-cell value">
+                    {{ autoscale ? "Enabled: " + autoscalePadding : "Disabled" }}
                 </div>
             </li>
             <li
@@ -142,6 +150,7 @@ export default {
             config: {},
             label: '',
             autoscale: '',
+            logMode: false,
             autoscalePadding: '',
             rangeMin: '',
             rangeMax: '',
@@ -172,6 +181,7 @@ export default {
         initConfiguration() {
             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) {

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

@@ -14,9 +14,22 @@
                 @change="updateForm('label')"
             ></div>
         </li>
-    </ul>
-    <ul class="l-inspector-part">
-        <h2>Y Axis Scaling</h2>
+        <li class="grid-row">
+            <div
+                class="grid-cell label"
+                title="Enable log mode."
+            >
+                Log mode
+            </div>
+            <div class="grid-cell value">
+                <!-- eslint-disable-next-line vue/html-self-closing -->
+                <input
+                    v-model="logMode"
+                    type="checkbox"
+                    @change="updateForm('logMode')"
+                />
+            </div>
+        </li>
         <li class="grid-row">
             <div
                 class="grid-cell label"
@@ -88,7 +101,7 @@
 </template>
 
 <script>
-import { objectPath, validate, coerce } from "./formUtil";
+import { objectPath, validate } from "./formUtil";
 import _ from "lodash";
 
 export default {
@@ -105,6 +118,7 @@ export default {
         return {
             label: '',
             autoscale: '',
+            logMode: false,
             autoscalePadding: '',
             rangeMin: '',
             rangeMax: '',
@@ -117,23 +131,23 @@ export default {
     },
     methods: {
         initialize: function () {
-            this.fields = [
-                {
-                    modelProp: 'label',
+            this.fields = {
+                label: {
                     objectPath: 'configuration.yAxis.label'
                 },
-                {
-                    modelProp: 'autoscale',
+                autoscale: {
                     coerce: Boolean,
                     objectPath: 'configuration.yAxis.autoscale'
                 },
-                {
-                    modelProp: 'autoscalePadding',
+                autoscalePadding: {
                     coerce: Number,
                     objectPath: 'configuration.yAxis.autoscalePadding'
                 },
-                {
-                    modelProp: 'range',
+                logMode: {
+                    coerce: Boolean,
+                    objectPath: 'configuration.yAxis.logMode'
+                },
+                range: {
                     objectPath: 'configuration.yAxis.range',
                     coerce: function coerceRange(range) {
                         if (!range) {
@@ -186,11 +200,12 @@ export default {
                         return true;
                     }
                 }
-            ];
+            };
         },
         initFormValues() {
             this.label = this.yAxis.get('label');
             this.autoscale = this.yAxis.get('autoscale');
+            this.logMode = this.yAxis.get('logMode');
             this.autoscalePadding = this.yAxis.get('autoscalePadding');
             const range = this.yAxis.get('range');
             if (!range) {
@@ -212,8 +227,8 @@ export default {
                 newVal = this[formKey];
             }
 
-            const oldVal = this.yAxis.get(formKey);
-            const formField = this.fields.find((field) => field.modelProp === formKey);
+            let oldVal = this.yAxis.get(formKey);
+            const formField = this.fields[formKey];
 
             const path = objectPath(formField.objectPath);
             const validationResult = validate(newVal, this.yAxis, formField.validate);
@@ -225,13 +240,17 @@ export default {
                 return;
             }
 
-            if (!_.isEqual(coerce(newVal, formField.coerce), coerce(oldVal, formField.coerce))) {
-                this.yAxis.set(formKey, coerce(newVal, formField.coerce));
+            newVal = formField.coerce?.(newVal) ?? newVal;
+            oldVal = formField.coerce?.(oldVal) ?? oldVal;
+
+            if (!_.isEqual(newVal, oldVal)) {
+                // TODO: Why do we mutate yAxis twice, once directly, once via objects.mutate?
+                this.yAxis.set(formKey, newVal);
                 if (path) {
                     this.openmct.objects.mutate(
                         this.domainObject,
                         path(this.domainObject, this.yAxis),
-                        coerce(newVal, formField.coerce)
+                        newVal
                     );
                 }
             }

src/plugins/plot/mathUtils.js

@@ -0,0 +1,44 @@
+/** The natural number `e`. */
+export const e = Math.exp(1);
+
+/**
+Returns the logarithm of a number, using the given base or the natural number
+`e` as base if not specified.
+@param {number} n
+@param {number=} base log base, defaults to e
+*/
+export function log(n, base = e) {
+    if (base === e) {
+        return Math.log(n);
+    }
+
+    return Math.log(n) / Math.log(base);
+}
+
+/**
+Returns the inverse of the logarithm of a number, using the given base or the
+natural number `e` as base if not specified.
+@param {number} n
+@param {number=} base log base, defaults to e
+*/
+export function antilog(n, base = e) {
+    return Math.pow(base, n);
+}
+
+/**
+A symmetric logarithm function. See https://github.com/nasa/openmct/issues/2297#issuecomment-1032914258
+@param {number} n
+@param {number=} base log base, defaults to e
+*/
+export function symlog(n, base = e) {
+    return Math.sign(n) * log(Math.abs(n) + 1, base);
+}
+
+/**
+An inverse symmetric logarithm function. See https://github.com/nasa/openmct/issues/2297#issuecomment-1032914258
+@param {number} n
+@param {number=} base log base, defaults to e
+*/
+export function antisymlog(n, base = e) {
+    return Math.sign(n) * (antilog(Math.abs(n), base) - 1);
+}

src/plugins/plot/tickUtils.js

@@ -1,3 +1,5 @@
+import { antisymlog, symlog } from "./mathUtils";
+
 const e10 = Math.sqrt(50);
 const e5 = Math.sqrt(10);
 const e2 = Math.sqrt(2);
@@ -40,6 +42,50 @@ function getPrecision(step) {
     return precision;
 }
 
+export function getLogTicks(start, stop, mainTickCount = 8, secondaryTickCount = 6) {
+    // log()'ed values
+    const mainLogTicks = ticks(start, stop, mainTickCount);
+
+    // original values
+    const scale = 1; // TODO get from UI, positive number above 0
+    const mainTicks = mainLogTicks.map(n => antisymlog(n / scale, 10));
+
+    const result = [];
+
+    let i = 0;
+    for (const logTick of mainLogTicks) {
+        result.push(logTick);
+
+        if (i === mainLogTicks.length - 1) {
+            break;
+        }
+
+        const tick = mainTicks[i];
+        const nextTick = mainTicks[i + 1];
+        const rangeBetweenMainTicks = nextTick - tick;
+
+        const secondaryLogTicks = ticks(
+            tick + rangeBetweenMainTicks / (secondaryTickCount + 1),
+            nextTick - rangeBetweenMainTicks / (secondaryTickCount + 1),
+            secondaryTickCount - 2
+        )
+            .map(n => scale * symlog(n, 10));
+
+        result.push(...secondaryLogTicks);
+
+        i++;
+    }
+
+    return result;
+}
+
+export function getLogTicks2(start, stop, count = 8) {
+    const scale = 1; // TODO get from UI, positive number above 0
+
+    return ticks(antisymlog(start / scale, 10), antisymlog(stop / scale, 10), count)
+        .map(n => scale * symlog(n, 10));
+}
+
 /**
  * Linear tick generation from d3-array.
  */