How to lock the horizontal movement of Line using FabricJS?

In this tutorial, we are going to learn how to lock the horizontal movement of a 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 whether we want the line object to move only in the Y-axis. This can be done by using the lockMovementX property.

Syntax

new fabric.Line(points: Array, { lockMovementX: Boolean }: 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 line object. Using this parameter origin, stroke width and a lot of other properties can be changed related to the object of which lockMovementX is a property.

Options Keys

lockMovementX ? This property accepts a Boolean value. If we assign it a ?true' value, then the object will no longer be able to move in the horizontal direction.

Default behaviour of a Line object in the canvas

Example

Let's see a code example to understand how we can move our line object in the X-axis or the Y-axis freely when lockMovementX property is not assigned a ?true' value.



<!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 Line object in the canvas</h2>
   <p>
      Drag the line object across the x-axis and y-axis to see that movement is allowed in both directions
   </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 lockMovementX as key with ?true' value

Example

In this example, we will see how we can lock the horizontal movement of a line object. By assigning the lockMovementX property a ?true' value, we essentially cease movement in the horizontal direction.



<!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 lockMovementX as key with ?true' value</h2>
   <p>
      Drag the line object across the x-axis and y-axis to see that movement is no longer allowed in the horizontal direction
   </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,
         lockMovementX: "true",
      });

      // Add it to the canvas
      canvas.add(line);
   </script>
</body>
</html>

Rahul Gurung

Updated on: 2022-10-25T08:41:56+05:30

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