FabricJS – How to set the dash pattern of the controlling corners of a Line?

In this tutorial, we are going to learn about how to set the dash pattern of controlling corners of Line using FabricJS. A Line element is one of the basic elements provided in FabricJS. It is used for creating straight lines. Because line elements are geometrically one-dimensional and do not contain an interior, they are never filled.

We can create a line object by creating an instance of fabric.Line, specifying the x and y coordinates of the line and adding it to the canvas. We can also specify a dash pattern for the controlling corners by using the cornerDashArray property.

Syntax

 new fabric.Line( points: Array, { cornerDashArray: Array }: Object)

Parameters

points − This parameter accepts an Array of points which determines the (x1, y1) and (x2, y2) values, those being the x- and y-axis coordinates of the start and end of the line respectively.
options (optional) − This parameter is an Object which provides additional customizations to our object. Using this parameter origin, stroke width and a lot of other properties can be changed related to the object of which cornerDashArray is a property.

Options Keys

cornerDashArray − This property accepts an Array which allows us to specify a dash pattern for the controlling corners. For example, if we pass an array with values [2,3], it means a dash pattern of 2px dash and 3px gap and repeating this pattern infinitely.

Default appearance of controlling corners

Example

Let’s see a code example that depicts the default appearance of the controlling corners of a line object. Since we have not used the cornerDashArray property, there is no dash pattern being displayed.


<!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 appearance of controlling corners</h2>
   <p>You can select the line object to see the default appearance of controlling corners</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 Line object
      var line = new fabric.Line([200, 100, 100, 40], {
         stroke: "blue",
         strokeWidth: 20,
      });
      
      // Add it to the canvas
      canvas.add(line);
   </script>
</body>
</html>

Passing cornerDashArray property as key

Example

In this example, we are passing the cornerDashArray property a value of [1,2,1]. This means that a dash pattern will be created such that there is a 1px long line, followed by a 2px gap, then again a 1px long line will be drawn and after which a 1px gap will be made and so on.


<!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 cornerDashArray property as key</h2>
   <p>You can select the line object to see the dash pattern of controlling corners</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 Line object
      var line = new fabric.Line([200, 100, 100, 40], {
         stroke: "blue",
         strokeWidth: 20,
         cornerColor: "#87a96b",
         cornerDashArray: [1, 2, 1],
      });
      
      // Add it to the canvas
      canvas.add(line);
   </script>
</body>
</html>