[ChartJs] Adding a better way to register Chartjs plugins

src/Chartjs/assets/dist/controller.js

@@ -1,20 +1,30 @@
 import { Controller } from '@hotwired/stimulus';
 import Chart from 'chart.js/auto';
 
+let isChartInitialized = false;
 class default_1 extends Controller {
     constructor() {
         super(...arguments);
         this.chart = null;
     }
     connect() {
+        if (!isChartInitialized) {
+            isChartInitialized = true;
+            this.dispatchEvent('init', {
+                Chart,
+            });
+        }
         if (!(this.element instanceof HTMLCanvasElement)) {
             throw new Error('Invalid element');
         }
         const payload = this.viewValue;
         if (Array.isArray(payload.options) && 0 === payload.options.length) {
             payload.options = {};
         }
-        this.dispatchEvent('pre-connect', { options: payload.options });
+        this.dispatchEvent('pre-connect', {
+            options: payload.options,
+            config: payload,
+        });
         const canvasContext = this.element.getContext('2d');
         if (!canvasContext) {
             throw new Error('Could not getContext() from Element');

src/Chartjs/assets/src/controller.ts

@@ -12,6 +12,8 @@
 import { Controller } from '@hotwired/stimulus';
 import Chart from 'chart.js/auto';
 
+let isChartInitialized = false;
+
 export default class extends Controller {
     declare readonly viewValue: any;
 
@@ -22,6 +24,13 @@ export default class extends Controller {
     private chart: Chart | null = null;
 
     connect() {
+        if (!isChartInitialized) {
+            isChartInitialized = true;
+            this.dispatchEvent('init', {
+                Chart,
+            });
+        }
+
         if (!(this.element instanceof HTMLCanvasElement)) {
             throw new Error('Invalid element');
         }
@@ -31,7 +40,10 @@ export default class extends Controller {
             payload.options = {};
         }
 
-        this.dispatchEvent('pre-connect', { options: payload.options });
+        this.dispatchEvent('pre-connect', {
+            options: payload.options,
+            config: payload,
+        });
 
         const canvasContext = this.element.getContext('2d');
         if (!canvasContext) {

src/Chartjs/assets/test/controller.test.ts

@@ -13,9 +13,18 @@ import { Application } from '@hotwired/stimulus';
 import { waitFor } from '@testing-library/dom';
 import ChartjsController from '../src/controller';
 
+// Kept track of globally, but just used in one test.
+// This is because, by the time that test has run, it is likely that the
+// chartjs:init event has already been dispatched. So, we capture it out here.
+let initCallCount = 0;
+
 const startChartTest = async (canvasHtml: string): Promise<{ canvas: HTMLCanvasElement, chart: Chart }> => {
     let chart: Chart | null = null;
 
+    document.body.addEventListener('chartjs:init', () => {
+        initCallCount++;
+    });
+
     document.body.addEventListener('chartjs:pre-connect', () => {
         document.body.classList.add('pre-connected');
     });
@@ -95,4 +104,51 @@ describe('ChartjsController', () => {
             expect(chart.options.showLines).toBe(true);
         });
     });
+
+    it('dispatches the events correctly', async () => {
+        let preConnectCallCount = 0;
+        let preConnectDetail: any = null;
+
+        document.body.addEventListener('chartjs:pre-connect', (event: any) => {
+            preConnectCallCount++;
+            preConnectDetail = event.detail;
+        });
+
+        await startChartTest(`
+            <canvas
+                data-testid="canvas"
+                data-controller="chartjs"
+                data-chartjs-view-value="&#x7B;&quot;type&quot;&#x3A;&quot;line&quot;,&quot;data&quot;&#x3A;&#x7B;&quot;labels&quot;&#x3A;&#x5B;&quot;January&quot;,&quot;February&quot;,&quot;March&quot;,&quot;April&quot;,&quot;May&quot;,&quot;June&quot;,&quot;July&quot;&#x5D;,&quot;datasets&quot;&#x3A;&#x5B;&#x7B;&quot;label&quot;&#x3A;&quot;My&#x20;First&#x20;dataset&quot;,&quot;backgroundColor&quot;&#x3A;&quot;rgb&#x28;255,&#x20;99,&#x20;132&#x29;&quot;,&quot;borderColor&quot;&#x3A;&quot;rgb&#x28;255,&#x20;99,&#x20;132&#x29;&quot;,&quot;data&quot;&#x3A;&#x5B;0,10,5,2,20,30,45&#x5D;&#x7D;&#x5D;&#x7D;,&quot;options&quot;&#x3A;&#x7B;&quot;showLines&quot;&#x3A;false&#x7D;&#x7D;"
+            ></canvas>
+        `);
+        expect(initCallCount).toBe(1);
+        expect(preConnectCallCount).toBe(1);
+        expect(preConnectDetail.options.showLines).toBe(false);
+        expect(preConnectDetail.config.type).toBe('line');
+        expect(preConnectDetail.config.data.datasets[0].data).toEqual([0, 10, 5, 2, 20, 30, 45]);
+
+        // add a second chart!
+        const canvas = document.createElement('canvas');
+        canvas.dataset.controller = 'chartjs';
+        canvas.dataset.chartjsViewValue = JSON.stringify({
+            type: 'line',
+            data: {
+                labels: ['January', 'February', 'March', 'April', 'May', 'June', 'July'],
+                datasets: [{
+                    label: 'My First dataset',
+                    backgroundColor: 'rgb(255, 99, 132)',
+                    borderColor: 'rgb(255, 99, 132)',
+                    data: [0, 10, 5, 2, 20, 30, 45],
+                }],
+            },
+            options: {
+                showLines: false,
+            },
+        });
+        document.body.appendChild(canvas);
+
+        await waitFor(() => expect(preConnectCallCount).toBe(2));
+        // still only initialized once
+        expect(initCallCount).toBe(1);
+    });
 });

src/Chartjs/doc/index.rst

@@ -98,18 +98,20 @@ First, install the plugin:
     $ npm install chartjs-plugin-zoom -D
 
     # or use yarn
-    $ yarn add chartjs-plugin-zoom -dev
+    $ yarn add chartjs-plugin-zoom --dev
 
 Then register the plugin globally. This can be done in your ``app.js`` file:
 
 .. code-block:: javascript
 
     // assets/app.js
-
-    import { Chart } from 'chart.js';
     import zoomPlugin from 'chartjs-plugin-zoom';
 
-    Chart.register(zoomPlugin);
+    // register globally for all charts
+    document.addEventListener('chartjs:init', function (event) {
+        const Chart = event.detail.Chart;
+        Chart.register(zoomPlugin);
+    });
 
     // ...
 
@@ -177,10 +179,11 @@ custom Stimulus controller:
 
         _onPreConnect(event) {
             // The chart is not yet created
-            console.log(event.detail.options); // You can access the chart options using the event details
+            // You can access the config that will be passed to "new Chart()"
+            console.log(event.detail.config);
 
             // For instance you can format Y axis
-            event.detail.options.scales = {
+            event.detail.config.options.scales = {
                 yAxes: [
                     {
                         ticks: {
@@ -213,6 +216,24 @@ Then in your render call, add your controller as an HTML attribute:
 
     {{ render_chart(chart, {'data-controller': 'mychart'}) }}
 
+There is also a ``chartjs:init`` event that is called just *one* time before your
+first chart is rendered. That's an ideal place to `register plugins globally <Using Plugins>`_
+or make other changes to any "static"/global part of Chart.js. For example,
+to add a global `Tooltip positioner`_:
+
+.. code-block:: javascript
+
+    // assets/app.js
+
+    // register globally for all charts
+    document.addEventListener('chartjs:init', function (event) {
+        const Chart = event.detail.Chart;
+        const Tooltip = Chart.registry.plugins.get('tooltip');
+        Tooltip.positioners.bottom = function(items) {
+            /* ... */
+        };
+    });
+
 Backward Compatibility promise
 ------------------------------
 
@@ -228,3 +249,4 @@ the Symfony framework: https://symfony.com/doc/current/contributing/code/bc.html
 .. _`a lot of plugins`: https://github.com/chartjs/awesome#plugins
 .. _`zoom plugin`: https://www.chartjs.org/chartjs-plugin-zoom/latest/
 .. _`zoom plugin documentation`: https://www.chartjs.org/chartjs-plugin-zoom/latest/guide/integration.html
+.. _`Tooltip positioner`: https://www.chartjs.org/docs/latest/samples/tooltip/position.html