HTML5 Canvas Custom Hit Detection Function Tutorial

To create a custom hit draw function for a shape with Konva, we can set
the drawHitFunc property. A hit draw function is the function that Konva
will use to draw a region used for hit detection. Using a custom draw hit
function can have several benefits, such as making the hit region larger
so that it’s easier for users to interact with a shape, making some portions
of a shape detectable and others not, or simplifying the hit draw function
in order to improve rendering performance.

Instructions: Mouseover, mouseout, mousedown, and mouseup over the star and
observe that the hit region is an over sized circle encompassing the shape.

Konva Custom_Hit_Region Demoview raw
<!DOCTYPE html>
<script src=""></script>
<meta charset="utf-8">
<title>Konva Custom Hit Function Demo</title>
body {
margin: 0;
padding: 0;
overflow: hidden;
background-color: #F0F0F0;
<div id="container"></div>
function writeMessage(message) {
var stage = new Konva.Stage({
container: 'container',
width: 300,
height: 300
var layer = new Konva.Layer();
var text = new Konva.Text({
x: 10,
y: 10,
fontFamily: 'Calibri',
fontSize: 24,
text: '',
fill: 'black'
var star = new Konva.Star({
x: stage.getWidth() / 2,
y: stage.getHeight() / 2,
numPoints: 7,
innerRadius: 50,
outerRadius: 70,
fill: 'red',
stroke: 'black',
strokeWidth: 4,
hitFunc: function(context) {
context.arc(0, 0, this.getOuterRadius() + 10, 0, Math.PI * 2, true);
star.on('mouseover', function() {
writeMessage('Mouseover star');
star.on('mouseout', function() {
writeMessage('Mouseout star');
star.on('mousedown', function() {
writeMessage('Mousedown star');
star.on('mouseup', function() {
writeMessage('Mouseup star');
// add the layer to the stage