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How to lock the vertical scaling of Triangle using FabricJS?
In this tutorial, we are going to learn how to lock the vertical 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 vertically. This can be done by using the lockScalingY property.
Syntax
new fabric.Triangle({ lockScalingY : 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 lockScalingY is a property.
Options 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 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 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 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: Locking Vertical Scaling
Passing lockScalingY as key with 'true' value
In this example, we will see how we can cease the ability of a Triangle object to scale vertically using the lockScalingY property. As we can see, although we can scale the triangle 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 'true' value</h2>
<p>You can see a not-allowed cursor if you try to scale the triangle in the y-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,
lockScalingY: true,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html>
Key Points
- The lockScalingY property only affects vertical scaling - horizontal scaling remains unaffected
- When vertical scaling is locked, users will see a not-allowed cursor when attempting to scale vertically
- This property is useful for maintaining aspect ratios or preventing unwanted deformation
Conclusion
The lockScalingY property provides precise control over triangle scaling in FabricJS. By setting it to true, you can prevent vertical scaling while preserving horizontal scaling functionality, ensuring your canvas objects maintain their intended proportions.
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