94 lines
2.3 KiB
JavaScript
94 lines
2.3 KiB
JavaScript
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function drawCross(ctx, hue) {
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ctx.beginPath();
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ctx.moveTo(200, 200);
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ctx.lineTo(300, 300);
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ctx.moveTo(300, 200);
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ctx.lineTo(200, 300);
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ctx.lineWidth = 5;
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ctx.strokeStyle = `hsla(${hue}, 100%, 50%, 1)`;
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ctx.stroke();
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}
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function drawCircle(ctx) {
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ctx.beginPath();
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// arc(x, y, radius, startAngle, endAngle)
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ctx.arc(75, 75, 50, 0, Math.PI * 2);
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ctx.stroke();
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}
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let startTime = undefined;
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let circles = [];
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let crosses = [];
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let pendingClicks = [];
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function animate(ctx, time) {
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if (!startTime) {
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startTime = time;
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}
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for (const evt of pendingClicks) {
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const h = Math.floor(Math.random() * 255);
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if (evt.kind == "circle") {
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circles.push({x: evt.x, y: evt.y, t: time, hue: h});
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} else if (evt.kind == "cross") {
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crosses.push({x: evt.x, y: evt.y, t: time, hue: h});
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}
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}
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pendingClicks = [];
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ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
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for (const circle of circles) {
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const dt = time - circle.t;
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drawAnimatedCircle(ctx, dt, circle.x, circle.y, circle.hue);
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}
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for (const cross of crosses) {
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drawCross(ctx, cross.hue);
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}
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window.requestAnimationFrame(time => animate(ctx, time));
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}
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function drawAnimatedCircle(ctx, dt, x, y, hue) {
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const end = dt*((2*Math.PI) / 1000);
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ctx.save();
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ctx.beginPath();
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ctx.arc(x, y, 50, 0, Math.min(end, 2*Math.PI));
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const percent = Math.trunc(100*Math.min(end, 2*Math.PI)/(2*Math.PI));
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ctx.strokeStyle = `hsla(${hue}, ${percent}%, 50%, 1)`;
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ctx.lineWidth = 5;
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ctx.stroke();
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ctx.restore();
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}
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function resizeCanvas(ctx) {
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ctx.canvas.width = window.innerWidth;
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ctx.canvas.height = window.innerHeight;
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}
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function init() {
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const canvas = document.getElementById("canvas");
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if (canvas.getContext) {
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const ctx = canvas.getContext("2d");
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resizeCanvas(ctx); // Init canvas
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window.addEventListener('resize', () => resizeCanvas(ctx));
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window.requestAnimationFrame(time => animate(ctx, time))
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canvas.addEventListener("click", (evt) => {
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const {clientX, clientY} = evt;
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pendingClicks.push({x: clientX, y: clientY, kind: "circle"});
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});
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canvas.addEventListener("contextmenu", (evt) => {
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evt.preventDefault();
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const {clientX, clientY} = evt;
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pendingClicks.push({x: clientX, y: clientY, kind: "cross"});
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});
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}
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}
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init();
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