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How to lock the vertical scaling of Rectangle using FabricJS?
In this tutorial, we are going to learn how to lock the vertical scaling of a Rectangle using FabricJS. Just as we can specify the position, colour, opacity and dimension of a rectangle object in the canvas, we can also specify whether we want to stop scaling an object vertically. This can be done by using the lockScalingY property.
Syntax
new fabric.Rect({ lockScalingY: Boolean })
Parameters
-
Options (optional) ? This parameter is an Object which provides additional customizations to our rectangle. 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 lockScalingY is a property.
Option Keys
-
lockScalingY ? This property accepts a Boolean value. If we assign it a "true" value, then the object's vertical scaling will be locked.
Example 1: Default Behaviour
Default behaviour of a Rectangle object in the canvas
Let's see a code example to understand the default behaviour of a Rectangle object when lockScalingY property is not used. Scaling the object in both horizontal and vertical directions is feasible.
<!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 Rectangle object in the canvas</h2>
<p>You can scale the rectangle in horizontal and vertical directions to verify that scaling in both directions is possible.</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 rectangle object
var rect = new fabric.Rect({
left: 155,
top: 90,
width: 170,
height: 70,
fill: "white",
padding: 9,
stroke: "#483d8b",
strokeWidth: 5,
});
// Add it to the canvas
canvas.add(rect);
</script>
</body>
</html>
Example 2: Locking Vertical Scaling
Passing lockScalingY as key with 'true' value
In this example, we will see how we can cease the ability of a Rectangle object to scale vertically using the lockScalingY property. As we can see, although we can scale the rectangle object horizontally, we are not allowed to perform the same action vertically.
<!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 lockScalingY as key with a "True" value</h2>
<p>You can see a not-allowed cursor if you try to scale the rectangle 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 rectangle object
var rect = new fabric.Rect({
left: 155,
top: 90,
width: 170,
height: 70,
fill: "white",
padding: 9,
stroke: "#483d8b",
strokeWidth: 5,
lockScalingY: true,
});
// Add it to the canvas
canvas.add(rect);
</script>
</body>
</html>
Key Differences
| Property | Default | With lockScalingY: true |
|---|---|---|
| Horizontal Scaling | Allowed | Allowed |
| Vertical Scaling | Allowed | Locked |
| Cursor on vertical handles | Resize cursor | Not-allowed cursor |
Conclusion
The lockScalingY property in FabricJS provides precise control over rectangle scaling behavior. Setting it to true prevents vertical scaling while maintaining horizontal scaling capabilities, useful for maintaining aspect ratios or design constraints.
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