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 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

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>

Updated on: 24-Jun-2022

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