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How to lock the horizontal movement of a Circle using FabricJS?
In this tutorial, we are going to learn how to lock the horizontal 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 Y-axis. This can be done by using the lockMovementX property.
Syntax
new fabric.Circle({ lockMovementX: 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 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.
Example 1: Default Behavior of Circle Movement
Let's see a code to understand how we can move our circle 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>How to lock the horizontal movement of a circle using FabricJS?</h2>
<p>Here you can select the circle and move it freely, as we have not applied the <b>lockMovementX</b> property. This is the default behavior. By default, <b>lockMovementX</b> is set to False. </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: Locking Horizontal Movement
In this example, we will see how we can lock the horizontal movement of a Circle 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>How to lock the horizontal movement of circle using FabricJS?</h2>
<p>Select the object and try to move it horizontally. You can't do that as we have restricted the horizontal movement by setting <b>lockMovementX</b> to True. You can however move the circle in vertical direction. </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,
lockMovementX: true
});
// Adding it to the canvas
canvas.add(circle);
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
</script>
</body>
</html>
Key Points
lockMovementX: false (default) - Circle can move freely in all directions
lockMovementX: true - Circle is restricted to vertical movement only
This property is useful for creating constrained user interactions in canvas applications
Conclusion
The lockMovementX property provides precise control over object movement in FabricJS. By setting it to true, you can restrict circles to vertical-only movement, which is useful for creating specific user interface behaviors and constrained interactions.
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