Render positions

No frame syncs, so flickers terribly, and performance is garbage. But it
works.

.eslintrc.js

@@ -31,7 +31,11 @@ module.exports = {
       asyncArrow: "always"
     }],
     "quote-props": ["error", "consistent"],
-    "quotes": ["error", "double"]
+    "quotes": ["error", "double"],
+    "sort-imports": ["error", {
+      "ignoreCase": true,
+      "allowSeparatedGroups": true
+    }]
   },
   overrides: [
     {

src/components/Canvas.tsx

@@ -0,0 +1,33 @@
+import React from "react"
+
+import CanvasContext from "./CanvasContext"
+
+export interface SystemCanvasProps {
+  height: number,
+  width: number,
+  children?: JSX.Element[]
+}
+
+function SystemCanvas({ height, width, children }: SystemCanvasProps) {
+  const canvasRef = React.useRef<HTMLCanvasElement>(null)
+  const [context, setContext] = React.useState<CanvasRenderingContext2D>(null)
+
+  React.useEffect(() => {
+    const context = canvasRef.current.getContext("2d")
+    context.save()
+    context.fillStyle = "black"
+    context.fillRect(0, 0, width, height)
+    context.restore()
+    setContext(context)
+  })
+
+  return (<div>
+    <CanvasContext.Provider value={ context }>
+      <canvas width={width} height={height} ref={canvasRef} style={{ width, height }} />
+      {children}
+    </CanvasContext.Provider>
+  </div>
+  )
+}
+
+export default SystemCanvas

src/components/CanvasContext.ts

@@ -0,0 +1,5 @@
+import React from "react"
+
+const CanvasContext = React.createContext<CanvasRenderingContext2D | null>(null)
+
+export default CanvasContext

src/components/Home.tsx

@@ -1,17 +1,19 @@
-import React, { useState, useEffect } from "react"
+import React, { useEffect, useState } from "react"
 
-import { Message, Object } from "@app/types"
+import { Body, Bounds, Message } from "@app/types"
+import Canvas from "./Canvas"
 import Client from "@app/client"
-import ObjectList from "./ObjectList"
+import RenderedBody from "./RenderedBody"
 
 function Home() {
-  const [objects, setObjects] = useState<Object[]>([])
+  const [bodies, setBodies] = useState<Body[]>([])
   const [iteration, setIteration] = useState(0)
   const [messageCount, setMessageCount] = useState(0)
   const [client, setClient] = useState<Client|null>(null)
+  const [bounds, setBounds] = useState<Bounds>(new Bounds(0, 0, 30, 30))
 
   const handleMessage = (msg: Message) => {
-    setObjects(msg.objects)
+    setBodies(msg.objects)
     setIteration(msg.iteration)
     setMessageCount((mc) => mc + 1)
   }
@@ -31,11 +33,29 @@ function Home() {
     }
   }, [client, messageCount])
 
+  useEffect(() => {
+    setBounds((bounds) => bodies.reduce(
+      (bounds, obj) => new Bounds(
+        Math.min(obj.x, bounds.minX),
+        Math.min(obj.y, bounds.minY),
+        Math.max(obj.x, bounds.maxX),
+        Math.max(obj.y, bounds.maxY)), bounds))
+  }, [bodies])
+
+  const actualBounds = new Bounds(0, 0, 300, 300)
+
   return (
     <>
       <h1>Hello, World!</h1>
-      <p>Iteration: { iteration }, message count: { messageCount }.</p>
-      <ObjectList objects={objects} />
+      <p>Iteration: { iteration }, message count: { messageCount }, nObjects: { bodies.length }.</p>
+      <Canvas height={actualBounds.height} width={actualBounds.width}>
+        {bodies.map((body) => <RenderedBody
+          key={body.id}
+          body={body}
+          bounds={bounds}
+          actualBounds={actualBounds}
+        />)}
+      </Canvas>
     </>
   )
 }

src/components/ObjectList.tsx

@@ -1,15 +0,0 @@
-import React from "react"
-
-import { Object } from "@app/types"
-
-export interface ObjectListProps {
-  objects: Object[]
-}
-
-function ObjectList({ objects }: ObjectListProps) {
-  return (<ul>
-    {objects.map((o) => <li key={o.id}>{o.name} @ ({o.x}, {o.y}, {o.z}) </li>)}
-  </ul>)
-}
-
-export default ObjectList

src/components/RenderedBody.tsx

@@ -0,0 +1,33 @@
+import React from "react"
+
+import { Body, Bounds } from "types"
+import CanvasContext from "./CanvasContext"
+
+export interface RenderedBodyProps {
+  body: Body
+  bounds: Bounds
+  actualBounds: Bounds
+}
+
+function RenderedBody({ body, bounds, actualBounds } : RenderedBodyProps): JSX.Element {
+  const context = React.useContext(CanvasContext)
+  if (context === null) {
+    return
+  }
+
+  const xScale = actualBounds.width / bounds.width
+  const yScale = actualBounds.height / bounds.width
+
+  context.save()
+  context.scale(xScale, yScale)
+  context.translate(-bounds.minX, -bounds.minY)
+  context.fillStyle = "white"
+  context.beginPath()
+  context.ellipse(body.x, body.y, 1 / xScale, 1 / yScale, 0, 0, Math.PI * 2)
+  context.fill()
+  context.restore()
+
+  return null
+}
+
+export default RenderedBody

src/index.tsx

@@ -1,6 +1,6 @@
-import React from 'react'
-import ReactDOM from 'react-dom'
+import React from "react"
+import ReactDOM from "react-dom"
 
-import Home from '@app/components/Home'
+import Home from "@app/components/Home"
 
-ReactDOM.render(<Home />, document.getElementById('root'))
+ReactDOM.render(<Home />, document.getElementById("root"))

src/types.ts

@@ -1,4 +1,4 @@
-export interface Object {
+export interface Body {
   name: string,
   id: number,
   x: number,
@@ -8,5 +8,22 @@ export interface Object {
 
 export interface Message {
   iteration: number,
-  objects: Object[]
+  objects: Body[]
+}
+
+export class Bounds {
+  minX: number
+  minY: number
+  maxX: number
+  maxY: number
+
+  constructor(minX: number, minY: number, maxX: number, maxY: number) {
+    this.minX = minX
+    this.minY = minY
+    this.maxX = maxX
+    this.maxY = maxY
+  }
+
+  get width() { return this.maxX - this.minX }
+  get height() { return this.maxY - this.minY }
 }