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How to lock the vertical skewing of a Triangle using FabricJS?
In this tutorial, we are going to learn how to lock the vertical skewing 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 skewing an object vertically. This can be done by using the lockSkewingY property.
Syntax
new fabric.Triangle({ lockSkewingY : 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 lockSkewingY is a property.
Options Keys
-
lockSkewingY ? This property accepts a Boolean value. If we assign it a 'true' value, then the object's vertical skewing will be locked.
Example 1: Default Behaviour of Triangle Skewing
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 lockSkewingY property is not used. Skewing the object in both horizontal and vertical directions is feasible by pressing the shift key and then dragging along the horizontal or 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>Default behaviour of a Triangle object in the canvas</h2>
<p>You can press the shift-key and drag the edge along the X or Y-axis to see that skewing is possible in both directions.</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 Skewing
Passing lockSkewingY as key with 'true' value
In this example, we will see how we can cease the ability of a triangle object to skew vertically using the lockSkewingY property. As we can see, although we can skew 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 lockSkewingY as key with 'true' value</h2>
<p>You can see that skewing along the y-axis is no longer feasible</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,
lockSkewingY: true,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html>
How It Works
The lockSkewingY property works by disabling the vertical skewing controls on the fabric object. When set to true, users can still perform horizontal skewing (along the X-axis) by holding Shift and dragging, but vertical skewing (along the Y-axis) is completely disabled. This is useful when you want to maintain the vertical proportions of your triangle while still allowing horizontal transformations.
Key Points
- By default,
lockSkewingYis set tofalse, allowing both horizontal and vertical skewing - Setting
lockSkewingY: trueonly locks vertical skewing; horizontal skewing remains available - Users need to hold the Shift key while dragging to activate skewing functionality
- This property is part of FabricJS's comprehensive object control system
Conclusion
The lockSkewingY property in FabricJS provides precise control over triangle object transformations by selectively disabling vertical skewing while preserving horizontal skewing capabilities. This feature is essential for maintaining design consistency when specific geometric constraints are required.
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