Get mouse coordinate in Dartpad

index.html

<canvas id="canvas" width="300" height="300"></canvas>
<div id="output"></div>

main.dart

import 'dart:html';

CanvasElement canvas = querySelector('#canvas');
CanvasRenderingContext2D context = canvas.getContext('2d');
DivElement output = querySelector("#output");

void main(){
  document.body.style.backgroundColor = "black";
  canvas.onMouseMove.listen((e) {
    output.text = "x:" + (e.client.x).toString() + ", y:" +(e.client.y).toString();
});
  
}

styles.css

html, body{
  color: white;
  font-size: 25px;
}