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How to lock the vertical movement of a Circle using FabricJS?
In this tutorial, we are going to learn how to lock the vertical movement of a Circle using FabricJS. Just as we can specify the position, colour, opacity and dimension of a circle object in the canvas, we can also specify whether we want it to move only in the X-axis. This can be done by using the lockMovementY property.
Syntax
new fabric.Circle({ lockMovementY: Boolean }: Object)
Parameters
-
options (optional) ? This parameter is an Object which provides additional customizations to our circle. Using this parameter, properties such as colour, cursor, stroke width and a lot of other properties can be changed related to the object of which lockMovementY is a property.
Option 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.
Example 1: Default Behavior
Default behaviour of a Circle object in the canvas
Let's see a code example to understand how we can move our circle 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 Circle Movement</h2>
<p>You can select the circle and move it freely. Here we have not applied the <b>lockMovementY</b> property.</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
var circle = new fabric.Circle({
left: 115,
top: 50,
fill: "white",
radius: 50,
stroke: "black",
strokeWidth: 5
});
// Adding it to the canvas
canvas.add(circle);
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
</script>
</body>
</html>
Example 2: Locked Vertical Movement
Passing lockMovementY as key with 'true' value
In this example we will see how we can lock the vertical movement of a Circle 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>Locking the vertical movement of circle using FabricJS</h2>
<p>Select the object and try to move it around. You will observe that the object can be moved horizontally, but its vertical movement is locked. Here we have set <b>lockMovementY</b> to True.</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
var circle = new fabric.Circle({
left: 115,
top: 50,
fill: "white",
radius: 50,
stroke: "black",
strokeWidth: 5,
lockMovementY: true
});
// Adding it to the canvas
canvas.add(circle);
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
</script>
</body>
</html>
Key Points
-
By default,
lockMovementYis set tofalse, allowing free movement in both directions. -
Setting
lockMovementY: truerestricts movement to horizontal only. -
The circle can still be moved along the X-axis even when vertical movement is locked.
-
This property is useful for creating interfaces where objects should only move in specific directions.
Conclusion
The lockMovementY property in FabricJS provides precise control over object movement by restricting vertical motion while preserving horizontal movement. This feature is essential for creating constrained drag interactions in canvas applications.
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