Fabric.js Polyline dirty Property

Last Updated : 22 Jan, 2021

In this article, we are going to see how to use the dirty property of the canvas Polyline in Fabric.js. The Polyline in Fabric.js 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. When the dirty property is set to true, then the object’s cache will be rerendered in the next render call.

To make it possible, we are going to use a JavaScript library called Fabric.js. After importing the library, we will create a canvas block in the body tag which will contain the Polyline. After this, we will initialize instances of Canvas and Polyline provided by Fabric.js, set the dirty property of Polyline and render the Polyline on the Canvas as given in the below example.

Syntax:

var polyline = new fabric.Polyline(Points, {  
    dirty: Boolean
});

Parameters: This property accepts a single parameter as mentioned above and described below:

dirty: It specifies whether the object’s cache will be rerendered in next render call or not.

The below example illustrates the Polyline dirty property in Fabric.js:

Example:

HTML

<html> 
<head> 
    <!-- Adding the FabricJS library -->
    <script src= 
"https://cdnjs.cloudflare.com/ajax/libs/fabric.js/4.3.0/fabric.min.js"> 
    </script> 
</head> 
<body> 
    <div style="text-align: center;width: 600px;"> 
        <h1 style="color: green;"> 
            GeeksforGeeks 
        </h1> 
        <b> 
            Fabric.js | Polyline dirty Property 
        </b> 
    </div> 
    <canvas id="canvas" width="600" height="200" 
            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: 200, 
                y: 10 
            }, 
            { 
                x: 250, 
                y: 50 
            }, { 
                x: 250, 
                y: 180 
            }, { 
                x: 150, 
                y: 180 
            }, { 
                x: 150, 
                y: 50 
            }, { 
                x: 200, 
                y: 10 
            }], { 
            cornerStyle: 'circle', 
            dirty: false 
        }); 
  
        // Render the polyline in canvas  
        canvas.add(polyline);  
    </script> 
</body> 
</html>