Stack overflow answer react

https://stackoverflow.com/questions/50999236/when-react-uses-canvas-drawing

by rishul matta

HTML

<div id="app"></div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

.done {
  color: rgba(0, 0, 0, 0.3);
  text-decoration: line-through;
}

input {
  margin-right: 5px;
}

React

class App extends React.Component {

constructor() {
	super();
  this.state = {
  	x: 0,
    y: 0
  }
}

 handleMouseMove(event) {
 	console.log('I am called');
     this.setState({
       x: event.clientX,
       y: event.clientY
     });
  }

updateCanvasCoordinates() {
	  const canvas = this.refs.canvas;
  canvas.width = 1000;
  canvas.height = 600;
  const ctx = canvas.getContext("2d");
  ctx.fillRect(this.state.x, this.state.y, 15,15)
}

componentDidUpdate() {
	this.updateCanvasCoordinates();
}

 componentDidMount() {
	this.updateCanvasCoordinates();
 }
 render() {

   return (
     <div>

      <canvas ref="canvas"
        onMouseMove={e=>this.handleMouseMove(e)}>
      and now what!
      </canvas>
     </div>

   );
 };
}

ReactDOM.render(<App />, document.querySelector("#app"))