How to enable selection of object only when it is fully contained in a selection area in FabricJS?

In this article, we are going to learn how to enable the selection of an object only when it is fully contained in the selection area using FabricJS. We can use the selectionFullyContained property to achieve this.

Syntax

new fabric.Canvas(element: HTMLElement|String, { selectionFullyContained: Boolean }: Object)

Parameters

element − This parameter is the <canvas> element itself which can be derived using Document.getElementById() or the id of the <canvas> element itself. The FabricJS canvas will be initialized on this element.
options (optional) − This parameter is an Object which provides additional customizations to our canvas. Using this parameter, properties such as color, cursor, border width, and a lot of other properties can be changed related to the canvas, of which selectionFullyContained is a property. It accepts a Boolean value which determines if the object should be selected only when it is fully contained in the selection area or not. It's default value is False.

Example 1

Passing the selectionFullyContained key with the value as False

Let's see a code example of the default behavior in FabricJS, which is, the object being selected despite not being fully contained in the selection area. In this example, we have passed the value of selectionFullyContained as False.

<!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>Enabling selection of an object only when it is fully contained in a selection area</h2>
   <p>Select a partial area around the object. The entire object would be selected even if you select a partial area containing the object.</p>
   <canvas id="canvas"></canvas>
   <script>
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas", {
         selectionFullyContained: false
      });
      // Creating an instance of the fabric.Rect class
      var circle = new fabric.Circle({
         left: 215,
         top: 100,
         radius: 50,
         fill: "orange",
      });
      // Adding it to the canvas
      canvas.add(circle);
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
   </script>
</body>
</html>

Example 2

Passing selectionFullyContained key to the class with the value as True

Let us see a code example where the value of selectionFullyContained property has been set to True. As we can see, the object will be selected only when it is fully contained in the selection area.

<!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>Enabling selection of an object only when it is fully contained in a selection area</h2>
   <p>Here you cannot select the object by selecting a partial area around the object. The object must be fully contained inside the selection area.</p>
   <canvas id="canvas"></canvas>
   <script>
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas", {
         selectionFullyContained: true
      });
      // Creating an instance of the fabric.Rect class
      var circle = new fabric.Circle({
         left: 215,
         top: 100,
         radius: 50,
         fill: "orange"
      });
      // Adding it to the canvas
      canvas.add(circle);
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
   </script>
</body>
</html>