How to show a context menu for HTML5 canvas shape?

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Do you want to show a context menu for a canvas shape?

To show a context menu we have to:

  1. Listen to contextmenu event on canvas container (stage)
  2. Prevent default browser behavior, so we don’t see native context menu
  3. Create our own context menu with Konva tools or regular html

Instructions: double click on the stage to create a circle. Try right click (context menu) on shapes for a menu.

Canvas_Context_Menu.htmlview raw
<!DOCTYPE html>
<html>
<head>
<script src="https://unpkg.com/[email protected]/konva.min.js"></script>
<meta charset="utf-8" />
<title>Konva Context Menu Demo</title>
<style>
body {
margin: 0;
padding: 0;
overflow: hidden;
background-color: #f0f0f0;
}

#menu {
display: none;
position: absolute;
width: 60px;
background-color: white;
box-shadow: 0 0 5px grey;
border-radius: 3px;
}

#menu button {
width: 100%;
background-color: white;
border: none;
margin: 0;
padding: 10px;
}

#menu button:hover {
background-color: lightgray;
}
</style>
</head>

<body>
<div id="container"></div>
<div id="menu">
<div><button id="pulse-button">Pulse</button><button id="delete-button">Delete</button></div>
</div>
<script>
var width = window.innerWidth;
var height = window.innerHeight;

var stage = new Konva.Stage({
container: 'container',
width: width,
height: height
});

var layer = new Konva.Layer();
stage.add(layer);

// add default shape
var shape = new Konva.Circle({
x: stage.width() / 2,
y: stage.height() / 2,
radius: 50,
fill: 'red',
shadowBlur: 10,
})
layer.add(shape);

layer.draw();


stage.on('dblclick dbltap', function() {
// add a new shape
var newShape = new Konva.Circle({
x: stage.getPointerPosition().x,
y: stage.getPointerPosition().y,
radius: 10 + Math.random() * 30,
fill: Konva.Util.getRandomColor(),
shadowBlur: 10
})
layer.add(newShape);
layer.draw();
});

// setup menu
let currentShape;
var menuNode = document.getElementById('menu');
document.getElementById('pulse-button').addEventListener('click', () => {
currentShape.to({
scaleX: 2,
scaleY: 2,
onFinish: () => {
currentShape.to({ scaleX: 1, scaleY: 1})
}
})
});

document.getElementById('delete-button').addEventListener('click', () => {
currentShape.destroy();
layer.draw();
});

window.addEventListener('click', () => {
// hide menu
menuNode.style.display = 'none';
})


stage.on('contextmenu', function(e) {
// prevent default behavior
e.evt.preventDefault();
if (e.target === stage) {
// if we are on empty place of the stage we will do nothing
return;
}
currentShape = e.target;
// show menu
menuNode.style.display = 'initial';
var containerRect = stage.container().getBoundingClientRect();
menuNode.style.top = containerRect.top + stage.getPointerPosition().y + 4 +'px';
menuNode.style.left = containerRect.left + stage.getPointerPosition().x + 4 + 'px';
});

</script>
</body>
</html>
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