Created
May 21, 2026 10:36
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Experimential Cross Tab Communication
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="UTF-8"> | |
| <meta name="viewport" content="width=device-width, initial-scale=1.0"> | |
| <title>Cross Tab Communication</title> | |
| <style> | |
| * { | |
| margin: 0; | |
| padding: 0; | |
| box-sizing: border-box; | |
| overflow: hidden; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <canvas id="default"></canvas> | |
| <script src="/index.js"></script> | |
| </body> | |
| </html> |
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| const TAB_ID = crypto.randomUUID(); | |
| const TAB_TIMEOUT = 100; | |
| const channel = new BroadcastChannel('cross-tab-com'); | |
| const canvas = document.getElementById('default'); | |
| const ctx = canvas.getContext('2d'); | |
| const posMap = {}; | |
| const lastSeenMap = {}; | |
| channel.addEventListener('message', (event) => { | |
| if (event.data.tabId === TAB_ID) return; | |
| posMap[event.data.tabId] = { x: event.data.x, y: event.data.y }; | |
| lastSeenMap[event.data.tabId] = performance.now(); | |
| }); | |
| function getWindowMiddlePosition() { | |
| const chromeHeight = window.outerHeight - window.innerHeight; | |
| return { | |
| x: window.screenX + window.innerWidth / 2, | |
| y: window.screenY + chromeHeight + window.innerHeight / 2, | |
| }; | |
| } | |
| function globalToLocal(globalX, globalY) { | |
| const chromeHeight = window.outerHeight - window.innerHeight; | |
| return { | |
| x: globalX - window.screenX, | |
| y: globalY - window.screenY - chromeHeight, | |
| }; | |
| } | |
| function post() { | |
| const { x, y } = getWindowMiddlePosition(); | |
| channel.postMessage({ tabId: TAB_ID, x, y }); | |
| } | |
| function period() { | |
| ctx.clearRect(0, 0, canvas.width, canvas.height); | |
| drawLines(); | |
| drawPoints(); | |
| requestAnimationFrame(period); | |
| } | |
| function drawLines() { | |
| const currentGlobal = getWindowMiddlePosition(); | |
| const currentLocal = globalToLocal( | |
| currentGlobal.x, | |
| currentGlobal.y | |
| ); | |
| const points = [{ x: currentLocal.x, y: currentLocal.y }]; | |
| for (const id in posMap) { | |
| const remoteGlobal = posMap[id]; | |
| const remoteLocal = globalToLocal(remoteGlobal.x, remoteGlobal.y); | |
| points.push({ x: remoteLocal.x, y: remoteLocal.y }); | |
| } | |
| ctx.strokeStyle = 'black'; | |
| ctx.lineWidth = 1; | |
| for (let i = 0; i < points.length; i++) { | |
| for (let j = i + 1; j < points.length; j++) { | |
| ctx.beginPath(); | |
| ctx.moveTo(points[i].x, points[i].y); | |
| ctx.lineTo(points[j].x, points[j].y); | |
| ctx.stroke(); | |
| } | |
| } | |
| } | |
| function drawPoints() { | |
| const currentGlobal = getWindowMiddlePosition(); | |
| const currentLocal = globalToLocal( | |
| currentGlobal.x, | |
| currentGlobal.y | |
| ); | |
| ctx.beginPath(); | |
| ctx.arc(currentLocal.x, currentLocal.y, 10, 0, 2 * Math.PI); | |
| ctx.fillStyle = 'red'; | |
| ctx.fill(); | |
| for (const id in posMap) { | |
| const remoteGlobal = posMap[id]; | |
| const remoteLocal = globalToLocal( | |
| remoteGlobal.x, | |
| remoteGlobal.y | |
| ); | |
| ctx.beginPath(); | |
| ctx.arc(remoteLocal.x, remoteLocal.y, 10, 0, 2 * Math.PI); | |
| ctx.fillStyle = 'blue'; | |
| ctx.fill(); | |
| } | |
| } | |
| function resizeCanvas() { | |
| canvas.width = window.outerWidth; | |
| canvas.height = window.outerHeight; | |
| } | |
| function cleanupDeadTabs() { | |
| const now = performance.now(); | |
| for (const id in lastSeenMap) { | |
| if (now - lastSeenMap[id] > TAB_TIMEOUT) { | |
| delete lastSeenMap[id]; | |
| delete posMap[id]; | |
| } | |
| } | |
| } | |
| window.addEventListener("resize", resizeCanvas); | |
| resizeCanvas(); | |
| period(); | |
| setInterval(post, 10); | |
| setInterval(cleanupDeadTabs, 100); |
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