UI trackpad scroll and pinch

by Andy Bulka

HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
    <title>Centered Zoom Trackpad Gesture Simulation</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            margin: 0;
            padding: 20px;
            overflow: hidden;
        }
        #canvas-container {
            width: 100%;
            height: 400px;
            overflow: hidden;
            position: relative;
            border: 1px solid #ccc;
        }
        canvas {
            position: absolute;
        }
        #log {
            margin-top: 20px;
            padding: 10px;
            background-color: #f0f0f0;
            border: 1px solid #ccc;
            height: 150px;
            overflow-y: auto;
        }
    </style>
</head>
<body>
    <h1>Centered Zoom Trackpad Gesture Simulation</h1>
    <div id="canvas-container">
        <canvas id="myCanvas"></canvas>
    </div>
    <div id="log"></div>

    <script>
        const canvas = document.getElementById('myCanvas');
        const ctx = canvas.getContext('2d');
        const container = document.getElementById('canvas-container');
        const logArea = document.getElementById('log');

        let scale = 1;
        let offsetX = 0;
        const baseRadius = 50;
        const verticalCenter = 200;

        function log(message) {
            const now = new Date();
            const timestamp = now.toLocaleTimeString() + '.' + now.getMilliseconds().toString().padStart(3, '0');
            logArea.innerHTML = `${timestamp}: ${message}<br>` + logArea.innerHTML;
            console.log(`${timestamp}: ${message}`);
        }

        function drawShapes() {
            canvas.width = 2000;
            canvas.height = 400;
            ctx.clearRect(0, 0, canvas.width, canvas.height);

            ctx.save();
            ctx.scale(scale, scale);
            ctx.translate(-offsetX / scale,...