Rewrite canvas to use React state management properly

blog/2024-11-15-playing-with-fire/1-introduction/GasketWeighted.tsx

@@ -1,6 +1,6 @@
-import {useEffect, useState} from "react";
-import Canvas from "../src/Canvas";
-import { Params, chaosGameWeighted } from "./chaosGameWeighted";
+import {useEffect, useState, useContext} from "react";
+import {PainterContext} from "../src/Canvas";
+import {chaosGameWeighted } from "./chaosGameWeighted";
 import TeX from '@matejmazur/react-katex';
 
 import styles from "../src/css/styles.module.css"
@@ -8,10 +8,6 @@ import styles from "../src/css/styles.module.css"
 type Transform = (x: number, y: number) => [number, number];
 
 export default function GasketWeighted() {
-    const image = new ImageData(600, 600);
-    const iterations = 100_000;
-    const step = 1000;
-
     const [f0Weight, setF0Weight] = useState<number>(1);
     const [f1Weight, setF1Weight] = useState<number>(1);
     const [f2Weight, setF2Weight] = useState<number>(1);
@@ -20,19 +16,14 @@ export default function GasketWeighted() {
     const f1: Transform = (x, y) => [(x + 1) / 2, y / 2];
     const f2: Transform = (x, y) => [x / 2, (y + 1) / 2];
 
-    const [game, setGame] = useState<Generator<ImageData>>(null);
+    const {setPainter} = useContext(PainterContext);
+
     useEffect(() => {
-        const params: Params = {
-            transforms: [
+        setPainter(chaosGameWeighted([
             [f0Weight, f0],
             [f1Weight, f1],
             [f2Weight, f2]
-            ],
-            image,
-            iterations,
-            step
-        }
-        setGame(chaosGameWeighted(params))
+        ]));
     }, [f0Weight, f1Weight, f2Weight]);
 
     const weightInput = (title, weight, setWeight) => (
@@ -47,7 +38,6 @@ export default function GasketWeighted() {
 
     return (
         <>
-            <Canvas width={image.width} height={image.height} painter={game}/>
             <div style={{paddingTop: '1em', display: 'grid', gridTemplateColumns: 'auto auto auto'}}>
                 {weightInput("F_0", f0Weight, setF0Weight)}
                 {weightInput("F_1", f1Weight, setF1Weight)}

blog/2024-11-15-playing-with-fire/1-introduction/chaosGame.js

@@ -1,4 +1,3 @@
-function Gasket() {
 // Hint: try increasing the iteration count
 const iterations = 10000;
 
@@ -9,10 +8,9 @@ function Gasket() {
     (x, y) => [x / 2, (y + 1) / 2]
 ]
 
-    const image = new ImageData(600, 600);
-
 function* chaosGame() {
-        var [x, y] = [randomBiUnit(), randomBiUnit()];
+    let image = new ImageData(500, 500);
+    let [x, y] = [randomBiUnit(), randomBiUnit()];
 
     for (var count = 0; count < iterations; count++) {
         const i = randomInteger(0, transforms.length);
@@ -24,13 +22,15 @@ function Gasket() {
         if (count % 1000 === 0)
             yield image;
     }
+
+    yield image;
 }
 
-    return (
-        <Canvas
-            width={image.width}
-            height={image.height}
-            painter={chaosGame()}/>
-    )
+// Wiring so the code above displays properly
+function Gasket() {
+    const {setPainter} = useContext(PainterContext);
+    setPainter(chaosGame());
+
+    return (<></>)
 }
 render(<Gasket/>)

blog/2024-11-15-playing-with-fire/1-introduction/chaosGameWeighted.ts

@@ -2,15 +2,12 @@
 import { randomBiUnit } from "../src/randomBiUnit";
 import { randomChoice } from "../src/randomChoice";
 import { plot } from "./plot"
-export type Transform = (x: number, y: number) => [number, number];
-export type Params = {
-    transforms: [number, Transform][],
-    image: ImageData,
-    iterations: number,
-    step: number
-}
+import {Transform} from "../src/transform";
+const iterations = 50_000;
+const step = 1000;
 // hidden-end
-export function* chaosGameWeighted({transforms, image, iterations, step}: Params) {
+export function* chaosGameWeighted(transforms: [number, Transform][]) {
+    let image = new ImageData(500, 500);
     var [x, y] = [randomBiUnit(), randomBiUnit()];
 
     for (let i = 0; i < iterations; i++) {

blog/2024-11-15-playing-with-fire/1-introduction/index.mdx

@@ -177,7 +177,9 @@ import Scope from './scope'
 
 import chaosGameSource from '!!raw-loader!./chaosGame'
 
+<!--
 <Playground scope={Scope} noInline={true}>{chaosGameSource}</Playground>
+-->
 
 <hr/>
 
@@ -198,7 +200,9 @@ import chaosGameWeightedSource from "!!raw-loader!./chaosGameWeighted";
 
 <CodeBlock language={'typescript'}>{chaosGameWeightedSource}</CodeBlock>
 
-import BrowserOnly from "@docusaurus/BrowserOnly";
 import GasketWeighted from "./GasketWeighted"
+import Canvas from "../src/Canvas"
 
-<BrowserOnly>{() => <GasketWeighted/>}</BrowserOnly>
+<Canvas width={500} height={500}>
+    <GasketWeighted/>
+</Canvas>

blog/2024-11-15-playing-with-fire/1-introduction/scope.tsx

@@ -1,12 +1,15 @@
+import {useContext} from "react";
 import { plot } from './plot';
 import { randomBiUnit } from '../src/randomBiUnit';
 import { randomInteger } from '../src/randomInteger';
-import Canvas from "../src/Canvas";
+import Canvas, {PainterContext} from "../src/Canvas";
 
 const Scope = {
+    Canvas,
+    PainterContext,
     plot,
     randomBiUnit,
     randomInteger,
-    Canvas
+    useContext,
 }
 export default Scope;

blog/2024-11-15-playing-with-fire/2-transforms/FlameBlend.tsx

@@ -1,4 +1,4 @@
-import {useState} from "react";
+import {useContext, useEffect, useState} from "react";
 import { blend } from "./blend";
 import { applyCoefs, Coefs } from "../src/coefs"
 import {randomBiUnit} from "../src/randomBiUnit";
@@ -19,7 +19,7 @@ import {
 } from "../src/params";
 import {randomChoice} from "../src/randomChoice";
 import {plotBinary} from "../src/plotBinary"
-import Canvas from "../src/Canvas"
+import {PainterContext} from "../src/Canvas"
 
 import styles from "../src/css/styles.module.css"
 
@@ -31,10 +31,11 @@ type VariationBlend = {
 }
 
 export default function FlameBlend() {
-    const image = new ImageData(400, 400);
     const quality = 2;
     const step = 5000;
 
+    const {width, height, setPainter} = useContext(PainterContext);
+
     const xform1Default: VariationBlend = {
         linear: 0,
         julia: 1,
@@ -73,6 +74,7 @@ export default function FlameBlend() {
         }
     }
 
+    const image = new ImageData(width, height);
     function* chaosGame() {
         let [x, y] = [randomBiUnit(), randomBiUnit()];
         const transforms: [number, Transform][] = [
@@ -97,6 +99,7 @@ export default function FlameBlend() {
 
         yield image;
     }
+    useEffect(() => setPainter(chaosGame()), [xform1Variations, xform2Variations, xform3Variations]);
 
     const variationEditor = (title, variations, setVariations) => {
         return (
@@ -127,16 +130,10 @@ export default function FlameBlend() {
     }
 
     return (
-        <>
-            <Canvas
-                width={image.width}
-                height={image.height}
-                painter={chaosGame()}/>
         <div style={{paddingTop: '1em', display: 'grid', gridTemplateColumns: 'auto auto auto auto'}}>
             {variationEditor("Transform 1", xform1Variations, setXform1Variations)}
             {variationEditor("Transform 2", xform2Variations, setXform2Variations)}
             {variationEditor("Transform 3", xform3Variations, setXform3Variations)}
         </div>
-        </>
     )
 }

blog/2024-11-15-playing-with-fire/2-transforms/index.mdx

@@ -119,7 +119,7 @@ import pdjSrc from '!!raw-loader!../src/pdj'
 
 <CodeBlock language={'typescript'}>{pdjSrc}</CodeBlock>
 
-### Blending
+## Blending
 
 Now, one variation is fun, but we can also combine variations in a single transform by "blending."
 Each variation receives the same $x$ and $y$ inputs, and we add together each variation's $x$ and $y$ outputs.
@@ -132,10 +132,15 @@ $$
 
 The formula looks intimidating, but it's not hard to implement:
 
-TODO: Blending implementation?
+import blendSource from "!!raw-loader!./blend";
+
+<CodeBlock language={'typescript'}>{blendSource}</CodeBlock>
 
 And with that in place, we have enough to render a first full fractal flame:
 
+import Canvas from "../src/Canvas";
 import FlameBlend from "./FlameBlend";
 
+<Canvas width={500} height={500}>
     <FlameBlend/>
+</Canvas>

blog/2024-11-15-playing-with-fire/src/Canvas.tsx

@@ -1,16 +1,53 @@
-import React, {useCallback, useEffect, useState} from "react";
+import React, {useCallback, useEffect, useState, createContext} from "react";
 import {useColorMode} from "@docusaurus/theme-common";
 
-interface Props {
+export interface PainterProps {
+    readonly width: number;
+    readonly height: number;
+    readonly setPainter: (painter: Iterator<ImageData>) => void;
+}
+
+/**
+ * Context provider for child elements to submit image iterator functions
+ * (painters) for rendering
+ */
+export const PainterContext = createContext<PainterProps>(null);
+
+interface CanvasProps {
     width: number;
     height: number;
-    painter: Iterator<ImageData>;
     children?: React.ReactNode;
 }
-export default function Canvas({width, height, painter, children}: Props) {
-    const {colorMode} = useColorMode();
-    const [image, setImage] = useState<[ImageData]>(null);
 
+/**
+ * Draw fractal flames to a canvas.
+ *
+ * This component is a bit involved because it attempts to solve
+ * a couple problems at the same time:
+ *  - Incrementally drawing an image to the canvas
+ *  - Interrupting drawing with new parameters on demand
+ *  - Dark mode
+ *
+ * Image iterators provide a means to draw incremental images;
+ * iterators can easily checkpoint state, and this component will
+ * request the next image on the next animation frame. As a result,
+ * the browser should be responsive even though we run CPU-heavy
+ * code on the main thread.
+ *
+ * Swapping a new iterator allows interrupting a render in progress,
+ * as the canvas completely repaints on each provided image.
+ *
+ * Finally, check whether dark mode is active, and invert the most
+ * recent image prior to painting if so.
+ *
+ * PainterContext is used to allow child elements to swap in
+ * new iterators.
+ *
+ * @param width Canvas draw width
+ * @param height Canvas draw height
+ * @param children Child elements
+ */
+export default function Canvas({width, height, children}: CanvasProps) {
     const [canvasCtx, setCanvasCtx] = useState<CanvasRenderingContext2D>(null);
     const canvasRef = useCallback(node => {
         if (node !== null) {
@@ -18,52 +55,93 @@ export default function Canvas({width, height, painter, children}: Props) {
         }
     }, []);
 
-    const paintImage = new ImageData(width, height);
-    const paint = () => {
-        if (!canvasCtx || !image) {
+    const {colorMode} = useColorMode();
+
+    // Holder objects are used to force re-painting even if the iterator
+    // returns a modified image with the same reference
+    type ImageHolder = { image?: ImageData };
+    const [imageHolder, setImageHolder] = useState<ImageHolder>({ image: null });
+    useEffect(() => {
+        const image = imageHolder.image;
+        if (!image) {
+            // No image is available, leave the canvas as-is
             return;
         }
 
-        for (const [index, value] of image[0].data.entries()) {
-            if (index % 4 === 3) {
-                // Alpha values are copied as-is
-                paintImage.data[index] = value;
-            } else {
-                // If dark mode is active, invert the color
-                paintImage.data[index] = colorMode === 'light' ? value : 255 - value;
-            }
+        if (!canvasCtx) {
+            // Canvas is not ready for the image we have,
+            // re-submit the image and wait for the ref to populate
+            setImageHolder({ image });
+            return;
         }
 
+        // If light mode is active, paint the image as-is
+        if (colorMode === 'light') {
+            canvasCtx.putImageData(image, 0, 0);
+            return;
+        }
+
+        // If dark mode is active, copy the image into a new buffer
+        // and invert colors prior to painting.
+        // Copy alpha values as-is.
+        const paintImage = new ImageData(image.width, image.height);
+        image.data.forEach((value, index) => {
+            const isAlpha = index % 4 === 3;
+            paintImage.data[index] = isAlpha ? value : 255 - value;
+        })
         canvasCtx.putImageData(paintImage, 0, 0);
-    }
-    useEffect(paint, [colorMode, image]);
+    }, [colorMode, imageHolder]);
 
-    const animate = () => {
+    // Image iterators (painters) are also in a holder; this allows
+    // re-submitting the existing iterator to draw the next frame,
+    // and also allows child components to over-write the iterator
+    // if a new set of parameters becomes available
+    // TODO(bspeice): Potential race condition?
+    // Not sure if it's possible for painters submitted by children
+    // to be over-ridden as a result re-submitting the
+    // existing iterator
+    type PainterHolder = { painter?: Iterator<ImageData> };
+    const [animHolder, setAnimHolder] = useState<PainterHolder>({ painter: null });
+    useEffect(() => {
+        const painter = animHolder.painter;
         if (!painter) {
             return;
         }
 
-        console.log("Animating");
-        const nextImage = painter.next().value;
-        if (nextImage) {
-            setImage([nextImage])
-            requestAnimationFrame(animate);
+        if (!canvasCtx) {
+            setAnimHolder({ painter });
+            return;
         }
+
+        const image = painter.next().value;
+        if (image) {
+            setImageHolder({ image });
+            setAnimHolder({ painter });
+        } else {
+            setAnimHolder({ painter: null });
         }
-    useEffect(animate, [painter, canvasCtx]);
+    }, [animHolder, canvasCtx]);
+
+    // Finally, child elements submit painters through a context provider
+    const [painter, setPainter] = useState<Iterator<ImageData>>(null);
+    useEffect(() => setAnimHolder({ painter }), [painter]);
 
     return (
         <>
+            <center>
                 <canvas
                     ref={canvasRef}
                     width={width}
                     height={height}
                     style={{
                         aspectRatio: width / height,
-                    width: '100%'
+                        width: '80%'
                     }}
                 />
+            </center>
+            <PainterContext.Provider value={{width, height, setPainter}}>
                 {children}
+            </PainterContext.Provider>
         </>
     )
 }

blog/2024-11-15-playing-with-fire/src/camera.ts

@@ -4,9 +4,7 @@
  * The way `flam3` actually calculates the "camera" for mapping a point
  * to its pixel coordinate is fairly involved - it also needs to calculate
  * zoom and rotation (see the bucket accumulator code in rect.c).
- * We'll make some simplifying assumptions:
- * - The final image is square
- * - We want to plot the range [-2, 2]
+ * We simplify things here by assuming a square image
  *
  * The reference parameters were designed in Apophysis, which uses the
  * range [-2, 2] by default (the `scale` parameter in XML defines the
@@ -15,7 +13,7 @@
  *
  * @param x point in the range [-2, 2]
  * @param y point in the range [-2, 2]
- * @param size image size
+ * @param size image width/height in pixels
  * @returns pair of pixel coordinates
  */
 export function camera(x: number, y: number, size: number): [number, number] {