HTML5 Canvas Custom Hit Detection Function Tutorial

To create a custom hit draw function for a shape with Konva, we can set
the hitFunc 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.

Also take a look into some best practices of writing custom sceneFunc that can be used for hitFunc too.

hitFunc is a function with two arguments: Konva.Context renderer and a shape instance.

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="[email protected]/konva.min.js"></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: window.innerWidth,
height: window.innerHeight

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.width() / 2,
y: stage.height() / 2,
numPoints: 7,
innerRadius: 50,
outerRadius: 70,
fill: 'red',
stroke: 'black',
strokeWidth: 4,
hitFunc: function(context) {
context.arc(0, 0, this.outerRadius() + 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