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How to lock the vertical movement of Line using FabricJS?
In this tutorial, we are going to learn how to lock the vertical movement 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 whether we want line object to move only in the X-axis. This can be done by using the lockMovementY property.
Syntax
new fabric.Line(points: Array, { lockMovementY: 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 object. Using this parameter origin, stroke width and a lot of other properties can be changed related to the object of which lockMovementY is a property.
Options Keys
lockMovementY − 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 vertical 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 lockMovementY 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 lockMovementY as key with ‘true’ value
Example
In this example, we will see how we can lock the vertical movement of a line object. By assigning the lockMovementY property a ‘true’ value, we essentially cease movement in the vertical 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 lockMovementY 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 vertical 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, lockMovementY: true, }); // Add it to the canvas canvas.add(line); </script> </body> </html>
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