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How to lock the rotation of a Triangle using FabricJS?
In this tutorial, we are going to learn how to lock the rotation of a Triangle using FabricJS. Just as we can specify the position, colour, opacity and dimension of a triangle object in the canvas, we can also specify whether we want it to rotate or not. This can be done by using the lockRotation property.
Syntax
new fabric.Triangle({ lockRotation : Boolean }: Object)
Parameters
-
Options (optional) ? This parameter is an Object which provides additional customizations to our triangle. Using this parameter, properties such as colour, cursor, stroke width, and a lot of other properties can be changed related to the object of which lockRotation is a property.
Options Keys
-
lockRotation ? This property accepts a Boolean value. If we assign it a 'true' value, then the object rotation will be locked.
Example 1: Default Behavior
Default behaviour of a Triangle object in the canvas
Let's see a code example to understand the default behaviour of a triangle object when lockRotation property is not used. By default, we can rotate a triangle object anticlockwise or clockwise.
<!DOCTYPE html>
<html>
<head>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
<h2>Default behaviour of a Triangle object in the canvas</h2>
<p>You can select triangle and try rotating it to see the default behavior.</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiate a triangle object
var triangle = new fabric.Triangle({
left: 105,
top: 70,
width: 90,
height: 80,
fill: "#746cc0",
stroke: "#967bb6",
strokeWidth: 5,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html>
Example 2: Using lockRotation
Passing lockRotation as key with 'true' value
In this example, we will see how we can cease the ability of a triangle object to rotate by using the lockRotation property. As we can see, as soon as we try to rotate the triangle object, a not-allowed cursor is shown. This means that the rotation action is no longer allowed.
<!DOCTYPE html>
<html>
<head>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
<h2>Passing lockRotation as key with 'true' value</h2>
<p>You can see that you are no longer allowed to rotate the triangle.</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiate a triangle object
var triangle = new fabric.Triangle({
left: 105,
top: 70,
width: 90,
height: 80,
fill: "#746cc0",
stroke: "#967bb6",
strokeWidth: 5,
lockRotation: true,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html>
Key Points
The lockRotation property accepts a Boolean value (true/false)
When set to
true, users cannot rotate the triangle objectA not-allowed cursor appears when attempting to rotate a locked triangle
By default, FabricJS allows rotation of all objects unless explicitly disabled
Conclusion
The lockRotation property in FabricJS provides a simple way to prevent triangle objects from being rotated by users. Set it to true to disable rotation or leave it as default to allow free rotation.
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