Fabric.js Polyline lockScalingY Property

Last Updated : 26 Aug, 2020

In this article, we are going to see how to lock the vertical scaling of the canvas polyline using FabricJS. The canvas polyline means the polyline is movable and can be stretched according to requirement. Further, the polyline can be customized when it comes to initial stroke color, height, width, fill color, or stroke width.

To make it possible we are going to use a JavaScript library called FabricJS. After importing the library, we will create a canvas block in the body tag that will contain the polyline. After this, we will initialize instances of Canvas and Polyline provided by FabricJS and lock vertical scaling of the canvas polyline using lockScalingY property and render the Polyline on the Canvas as given in the example below.

Syntax:

var polyline = new fabric.Polyline(
    points, {lockScalingY: boolean}
)

Parameters: This function accepts two parameters as mentioned above and described below:

points: It holds the starting and ending coordinates for all the points of the polyline.
lockScalingY: It is a boolean value that specifies whether to lock vertical scaling of canvas.

Below example illustrate the Polyline lockScalingY Property in JavaScript:

Example:

Javascript

<!DOCTYPE html> 
<html> 
  
<head> 
    <!-- Loading the FabricJS library -->
    <script src= 
"https://cdnjs.cloudflare.com/ajax/libs/fabric.js/3.6.2/fabric.min.js"> 
    </script> 
</head> 
  
<body> 
    <div style="text-align: center; 
        width: 600px;"> 
        <h1 style="color: green;"> 
            GeeksforGeeks 
        </h1> 
        <b> 
            Fabric.js | Polyline lockScalingY Property 
        </b> 
    </div> 
  
    <canvas id="canvas" width="600" height="300" 
        style="border:1px solid #000000;"> 
    </canvas> 
      
    <script> 
  
        // Initiate a Canvas instance  
        var canvas = new fabric.Canvas("canvas"); 
  
        // Initiate a Polyline instance  
        var polyline = new fabric.Polyline([ 
            { 
                x: 300, 
                y: 60 
            }, 
            { 
                x: 350, 
                y: 100 
            }, { 
                x: 350, 
                y: 230 
            }, { 
                x: 250, 
                y: 230 
            }, { 
                x: 250, 
                y: 100 
            }, { 
                x: 300, 
                y: 60 
            }], { 
  
            // Disable scaling 
            // along the y-axis 
            lockScalingY: true 
        }); 
  
        // Render the Polyline in canvas  
        canvas.add(polyline);  
    </script> 
</body> 
  
</html> 