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FabricJS - How to move a Line object one step down in the draw object stack?
FabricJS - How to move a Line object one step down in the draw object stack?
In this tutorial, we will learn how to move a Line object one step down the draw object stack using FabricJS. Line element is one of the basic elements provided in FabricJS. It is used to create straight lines. Since line elements are geometrically one-dimensional and contain no interiors, they are never filled. We can create a line object by creating a fabric.Line instance, specifying the x and y coordinates of the line and adding it to the canvas. To move the Line object one step down the draw object stack, we use the sendBackwards method.
Syntax
sendBackwards(intersecting: Boolean): fabric.Object
Parameters
Intersect - This parameter accepts Boolean valuesWhen specified as a "true" value, the object will be sent behind the next lower intersecting object. If the value is "false", it normally sends the object after the next object on the stack. This parameter is optional.
Using the sendBackwards method
Example
Let’s look at a code example to see how to use the sendBackwards method time output. sendBackwards method moves the object one step down in the draw object stack. In this example, line2 is sent after line1 using the sendBackwards method.
<!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>Using sendBackwards method</h2>
<p>
You can see that line2 (red) has been moved down in the stack of drawn objects
</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 Line object
var line1 = new fabric.Line([200, 100, 100, 40], {
stroke: "blue",
strokeWidth: 20,
});
// Initiate another Line object
var line2 = new fabric.Line([200, 70, 70, 40], {
stroke: "red",
strokeWidth: 20,
});
// Add both to the canvas
canvas.add(line1);
canvas.add(line2);
// Using sendBackwards method
line2.sendBackwards();
</script>
</body>
</html>
Use the sendBackwards method and enable three objects and enable the intersection key
Example
In this example, we use three line objects, line1, line2 and line3. Although they have been added to the canvas in numerical order, line3 is clearly behind line1. This is because we are using the sendBackwards method with intersection key enabled, which sends line3 to its next lower intersection object (i.e. line1) later. p>
<!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>Using sendBackwards method with three objects and intersection key enabled</h2>
<p>
You can see that the green line now lies behind the blue line which is line number 1
</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 Line object
var line1 = new fabric.Line([200, 100, 100, 40], {
stroke: "blue",
strokeWidth: 20,
});
// Initiate another Line object
var line2 = new fabric.Line([500, 70, 400, 40], {
stroke: "red",
strokeWidth: 20,
});
// Initiate another Line object
var line3 = new fabric.Line([200, 30, 30, 90], {
stroke: "green",
strokeWidth: 20,
});
// Add them all to the canvas
canvas.add(line1);
canvas.add(line2);
canvas.add(line3);
// Using sendBackwards method
line3.sendBackwards(true);
</script>
</body>
</html>
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