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How to lock the horizontal scaling of Triangle using FabricJS?
In this tutorial, we are going to learn how to lock the horizontal scaling of a Triangle using FabricJS. Just as we can specify the position, colour, opacity and dimension of a triangle object in the canvas, we can also specify whether we want to stop scaling an object horizontally. This can be done by using the lockScalingX property.
Syntax
new fabric.Triangle({ lockScalingX : Boolean }: Object)
Parameters
-
Options (optional) ? This parameter is an Object which provides additional customizations to our triangle. 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 lockScalingX is a property.
Options Keys
-
lockScalingX ? This property accepts a Boolean value. If we assign it a 'true' value, then the object's horizontal scaling will be locked. When set to false (default), horizontal scaling is allowed.
Example 1: Default Behavior
Default behaviour of a Triangle object in the canvas
Let's see a code example to understand the default behaviour of a Triangle object when lockScalingX 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 Triangle object in the canvas</h2>
<p>You can scale the triangle 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 triangle object
var triangle = new fabric.Triangle({
left: 105,
top: 70,
width: 90,
height: 80,
fill: "#746cc0",
stroke: "#967bb6",
strokeWidth: 5,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html>
Example 2: Using lockScalingX Property
Passing lockScalingX as key with 'true' value
In this example, we will see how we can cease the ability of a triangle object to scale horizontally using the lockScalingX property. As we can see, although we can scale the triangle object vertically, we are not allowed to perform the same action horizontally.
<!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 lockScalingX as key with 'true' value</h2>
<p>You can see a not-allowed cursor if you try to scale the triangle 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 triangle object
var triangle = new fabric.Triangle({
left: 105,
top: 70,
width: 90,
height: 80,
fill: "#746cc0",
stroke: "#967bb6",
strokeWidth: 5,
lockScalingX: true,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html>
Key Points
The
lockScalingXproperty only affects horizontal scaling - vertical scaling remains unaffectedWhen set to
true, users will see a "not-allowed" cursor when attempting horizontal scalingThis property is useful for maintaining aspect ratios or design constraints in your FabricJS applications
The property can be combined with
lockScalingYto lock both horizontal and vertical scaling
Conclusion
The lockScalingX property in FabricJS provides precise control over horizontal scaling of triangle objects. By setting it to true, you can prevent users from stretching or compressing the triangle horizontally while still allowing vertical scaling and other transformations.
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