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React component to redraw a canvas when resized
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import React from "react"; | |
const scaleWidth = 500; | |
const scaleHeight = 500; | |
function draw(canvas, scaleX, scaleY) { | |
const context = canvas.getContext("2d"); | |
context.scale(scaleX, scaleY); | |
context.clearRect(0, 0, canvas.clientWidth, canvas.clientHeight); | |
context.beginPath(); | |
context.setLineDash([]); | |
context.lineWidth = 2; | |
context.strokeStyle = "red"; | |
context.moveTo(0, 100); | |
context.lineTo(scaleWidth, 100); | |
context.moveTo(0, 400); | |
context.lineTo(scaleWidth, 400); | |
context.stroke(); | |
context.lineWidth = 1; | |
context.strokeStyle = "blue"; | |
context.fillStyle = "blue"; | |
context.rect(200, 200, 100, 100); | |
context.fill(); | |
context.closePath(); | |
} | |
function CanvasDraw() { | |
const [scale, setScale] = React.useState({ x: 1, y: 1 }); | |
const canvas = React.useRef(null); | |
const calculateScaleX = () => (!canvas.current ? 0 : canvas.current.clientWidth / scaleWidth); | |
const calculateScaleY = () => (!canvas.current ? 0 : canvas.current.clientHeight / scaleHeight); | |
const resized = () => { | |
canvas.current.width = canvas.current.clientWidth; | |
canvas.current.height = canvas.current.clientHeight; | |
setScale({ x: calculateScaleX(), y: calculateScaleY() }); | |
}; | |
React.useEffect(() => resized(), []); | |
React.useEffect(() => { | |
const currentCanvas = canvas.current; | |
currentCanvas.addEventListener("resize", resized); | |
return () => currentCanvas.removeEventListener("resize", resized); | |
}); | |
React.useEffect(() => { | |
draw(canvas.current, scale.x, scale.y); | |
}, [scale]); | |
return <canvas ref={canvas} style={{ width: "100%", height: "100%" }} />; | |
} | |
export default CanvasDraw; |
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