Cross Tab Communication

# Experimential Cross Tab Communication > Source: > Published: 2026-05-21 10:36:39+00:00 index.html This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters Show hidden characters Cross Tab Communication

index.js This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters Show hidden characters 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);