perf: reduce rerenders

src/chart.tsx

@@ -1,16 +1,14 @@
-import React, {
-  useEffect,
-  useState,
-  useRef,
-  useImperativeHandle,
-  useMemo,
-  forwardRef,
-} from 'react';
-import type { Ref, MouseEvent } from 'react';
+import React, { useEffect, useRef, useState, forwardRef } from 'react';
+import type { ForwardedRef, MouseEvent } from 'react';
 import ChartJS from 'chart.js/auto';
 import type { ChartData, ChartType, DefaultDataPoint } from 'chart.js';
 
-import { Props, ChartJSOrUndefined, TypedChartComponent } from './types';
+import type { Props, TypedChartComponent } from './types';
+import { reforwardRef, setNextDatasets } from './utils';
+
+const noopData = {
+  datasets: [],
+};
 
 function ChartComponent<
   TType extends ChartType = ChartType,
@@ -22,7 +20,7 @@ function ChartComponent<
     width = 300,
     redraw = false,
     type,
-    data,
+    data: dataProp,
     options,
     plugins = [],
     getDatasetAtEvent,
@@ -32,45 +30,49 @@ function ChartComponent<
     onClick: onClickProp,
     ...props
   }: Props<TType, TData, TLabel>,
-  ref: Ref<ChartJS<TType, TData, TLabel>>
+  ref: ForwardedRef<ChartJS<TType, TData, TLabel>>
 ) {
-  type TypedChartJS = ChartJSOrUndefined<TType, TData, TLabel>;
+  type TypedChartJS = ChartJS<TType, TData, TLabel>;
   type TypedChartData = ChartData<TType, TData, TLabel>;
 
-  const canvas = useRef<HTMLCanvasElement>(null);
+  const canvasRef = useRef<HTMLCanvasElement>(null);
+  const chartRef = useRef<TypedChartJS | null>();
+  /**
+   * In case `dataProp` is function use internal state
+   */
+  const [computedData, setComputedData] = useState<TypedChartData>();
+  const data: TypedChartData =
+    computedData || (typeof dataProp === 'function' ? noopData : dataProp);
 
-  const computedData = useMemo<TypedChartData>(() => {
-    if (typeof data === 'function') {
-      return canvas.current
-        ? data(canvas.current)
-        : {
-            datasets: [],
-          };
-    } else return data;
-  }, [data, canvas.current]);
+  const renderChart = () => {
+    if (!canvasRef.current) return;
 
-  const [chart, setChart] = useState<TypedChartJS>();
+    chartRef.current = new ChartJS(canvasRef.current, {
+      type,
+      data,
+      options,
+      plugins,
+    });
 
-  useImperativeHandle<TypedChartJS, TypedChartJS>(ref, () => chart, [chart]);
+    reforwardRef(ref, chartRef.current);
+  };
 
-  const renderChart = () => {
-    if (!canvas.current) return;
-
-    setChart(
-      new ChartJS(canvas.current, {
-        type,
-        data: computedData,
-        options,
-        plugins,
-      })
-    );
+  const destroyChart = () => {
+    reforwardRef(ref, null);
+
+    if (chartRef.current) {
+      chartRef.current.destroy();
+      chartRef.current = null;
+    }
   };
 
   const onClick = (event: MouseEvent<HTMLCanvasElement>) => {
     if (onClickProp) {
       onClickProp(event);
     }
 
+    const { current: chart } = chartRef;
+
     if (!chart) return;
 
     getDatasetAtEvent &&
@@ -105,80 +107,54 @@ function ChartComponent<
       );
   };
 
-  const updateChart = () => {
-    if (!chart) return;
-
-    if (options) {
-      chart.options = { ...options };
+  /**
+   * In case `dataProp` is function,
+   * then update internal state
+   */
+  useEffect(() => {
+    if (typeof dataProp === 'function' && canvasRef.current) {
+      setComputedData(dataProp(canvasRef.current));
     }
+  }, [dataProp]);
 
-    if (!chart.config.data) {
-      chart.config.data = computedData;
-      chart.update();
-      return;
+  useEffect(() => {
+    if (!redraw && chartRef.current && options) {
+      chartRef.current.options = { ...options };
     }
+  }, [redraw, options]);
 
-    const { datasets: newDataSets = [], ...newChartData } = computedData;
-    const { datasets: currentDataSets = [] } = chart.config.data;
-
-    // copy values
-    Object.assign(chart.config.data, newChartData);
-
-    chart.config.data.datasets = newDataSets.map((newDataSet: any) => {
-      // given the new set, find it's current match
-      const currentDataSet = currentDataSets.find(
-        d => d.label === newDataSet.label && d.type === newDataSet.type
-      );
+  useEffect(() => {
+    if (!redraw && chartRef.current) {
+      chartRef.current.config.data.labels = data.labels;
+    }
+  }, [redraw, data.labels]);
 
-      // There is no original to update, so simply add new one
-      if (!currentDataSet || !newDataSet.data) return { ...newDataSet };
-
-      if (!currentDataSet.data) {
-        // @ts-expect-error Need to refactor
-        currentDataSet.data = [];
-      } else {
-        // @ts-expect-error Need to refactor
-        currentDataSet.data.length = newDataSet.data.length;
-      }
-
-      // copy in values
-      Object.assign(currentDataSet.data, newDataSet.data);
-
-      // apply dataset changes, but keep copied data
-      Object.assign(currentDataSet, {
-        ...newDataSet,
-        data: currentDataSet.data,
-      });
-      return currentDataSet;
-    });
+  useEffect(() => {
+    if (!redraw && chartRef.current && data.datasets) {
+      setNextDatasets(chartRef.current.config.data, data.datasets);
+    }
+  }, [redraw, data.datasets]);
 
-    chart.update();
-  };
+  useEffect(() => {
+    if (!chartRef.current) return;
 
-  const destroyChart = () => {
-    if (chart) chart.destroy();
-  };
+    if (redraw) {
+      destroyChart();
+      setTimeout(renderChart);
+    } else {
+      chartRef.current.update();
+    }
+  }, [redraw, options, data.labels, data.datasets]);
 
   useEffect(() => {
     renderChart();
 
     return () => destroyChart();
   }, []);
 
-  useEffect(() => {
-    if (redraw) {
-      destroyChart();
-      setTimeout(() => {
-        renderChart();
-      }, 0);
-    } else {
-      updateChart();
-    }
-  });
-
   return (
     <canvas
-      ref={canvas}
+      ref={canvasRef}
       role='img'
       height={height}
       width={width}

src/utils.ts

@@ -0,0 +1,39 @@
+import type { ForwardedRef } from 'react';
+import type {
+  ChartType,
+  ChartData,
+  DefaultDataPoint,
+  ChartDataset,
+} from 'chart.js';
+
+export function reforwardRef<T>(ref: ForwardedRef<T>, value: T) {
+  if (typeof ref === 'function') {
+    ref(value);
+  } else if (ref) {
+    ref.current = value;
+  }
+}
+
+export function setNextDatasets<
+  TType extends ChartType = ChartType,
+  TData = DefaultDataPoint<TType>,
+  TLabel = unknown
+>(
+  currentData: ChartData<TType, TData, TLabel>,
+  nextDatasets: ChartDataset<TType, TData>[]
+) {
+  currentData.datasets = nextDatasets.map(nextDataset => {
+    // given the new set, find it's current match
+    const currentDataset = currentData.datasets.find(
+      dataset =>
+        dataset.label === nextDataset.label && dataset.type === nextDataset.type
+    );
+
+    // There is no original to update, so simply add new one
+    if (!currentDataset || !nextDataset.data) return nextDataset;
+
+    Object.assign(currentDataset, nextDataset);
+
+    return currentDataset;
+  });
+}

stories/Chart.tsx

@@ -93,3 +93,10 @@ ClickEvents.argTypes = {
   onElementClick: { action: 'element clicked' },
   onElementsClick: { action: 'elements clicked' },
 };
+
+export const Redraw = args => <Chart {...args} />;
+
+Redraw.args = {
+  data: data.multiTypeData,
+  redraw: true,
+};

stories/Doughnut.tsx

@@ -1,4 +1,4 @@
-import React from 'react';
+import React, { useState, useEffect } from 'react';
 import { Doughnut } from '../src';
 import { data } from './Doughnut.data';
 
@@ -19,3 +19,21 @@ export const Default = args => <Doughnut {...args} />;
 Default.args = {
   data,
 };
+
+export const Rotation = args => {
+  const [rotation, setRotation] = useState(0);
+
+  useEffect(() => {
+    const interval = setInterval(() => {
+      setRotation(rotation => rotation + 90);
+    }, 3000);
+
+    return () => clearInterval(interval);
+  });
+
+  return <Doughnut {...args} options={{ rotation }} />;
+};
+
+Rotation.args = {
+  data,
+};

stories/Pie.data.ts

@@ -1,3 +1,5 @@
+import faker from 'faker';
+
 export const data = {
   labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'],
   datasets: [
@@ -24,3 +26,10 @@ export const data = {
     },
   ],
 };
+
+export function randomDataset() {
+  return {
+    value: faker.datatype.number({ min: -100, max: 100 }),
+    color: faker.internet.color(),
+  };
+}

stories/Pie.tsx

@@ -1,6 +1,6 @@
-import React from 'react';
+import React, { useState } from 'react';
 import { Pie } from '../src';
-import { data } from './Pie.data';
+import { data, randomDataset } from './Pie.data';
 
 export default {
   title: 'Components/Pie',
@@ -19,3 +19,37 @@ export const Default = args => <Pie {...args} />;
 Default.args = {
   data,
 };
+
+export const Dynamic = args => {
+  const [datasets, setDatasets] = useState(() => [randomDataset()]);
+  const onAdd = () => {
+    setDatasets(datasets => [...datasets, randomDataset()]);
+  };
+  const onRemove = () => {
+    setDatasets(datasets => datasets.slice(0, -1));
+  };
+  const data = {
+    labels: datasets.map((_, i) => `#${i}`),
+    datasets: [
+      {
+        data: datasets.map(({ value }) => value),
+        backgroundColor: datasets.map(({ color }) => color),
+      },
+    ],
+  };
+
+  return (
+    <>
+      <Pie {...args} data={data} />
+      <button onClick={onRemove}>Remove</button>
+      <button onClick={onAdd}>Add</button>
+      <ul>
+        {datasets.map(({ value, color }, i) => (
+          <li key={i} style={{ backgroundColor: color }}>
+            {value}
+          </li>
+        ))}
+      </ul>
+    </>
+  );
+};