Node annotations in EJ2 JavaScript Diagram control

15 Dec 202417 minutes to read

Diagram allows you to customize the position and appearance of the annotation efficiently. Annotation can be aligned relative to the node boundaries. It has Margin, Offset, Horizontal, and Vertical alignment properties. It is quite tricky when all four alignments are used together but gives more control over alignments properties of the ShapeAnnotation class. Annotations of a node can be positioned using the following properties of ShapeAnnotation.

Offset
HorizontalAlignment
VerticalAlignment
Margin

Set annotation offset and size

The offset property of an annotation is used to align annotations based on fractional values. The offset can be customized by modifying the x and y values of the offset property. By default, the annotation offset is set to 0.5 on both the x and y axes.

By default, the size of the annotation is calculated based on its content. If you want to set the size externally, you can do so using the width and height properties of annotation.

The following code shows how to set offset, height and width for the annotation.

index.js
index.html
var node = {
    // Position of the node
    offsetX: 250,
    offsetY: 250,
    // Size of the node
    width: 100,
    height: 100,
    style: {
      fill: '#6BA5D7',
      strokeColor: 'white',
    },
    // Sets the annotation for the node
    annotations: [
      {
        // Sets the content for the annotation
        content: 'Annotation long annotation content',
        //Sets the offset for the content
        offset: { x: 0, y: 1 },
        height: 100,
        width: 100,
      },
    ],
  };
  // initialize Diagram component
  
  var diagram = new ej.diagrams.Diagram(
    {
      width: '100%',
      height: '600px',
      nodes: [node],
    },
    '#element'
  );
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Diagram</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-buttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-popups/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-splitbuttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-diagrams/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-navigations/styles/fabric.css" rel="stylesheet">
    
<script src="https://cdn.syncfusion.com/ej2/28.2.3/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <div id="element"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

Update annotation offset at runtime

The annotation offset can be updated dynamically at runtime. To update the annotation offset, fetch the annotation you want to update and modify its offset.

index.js
index.html
var node = {
  // Position of the node
  offsetX: 250,
  offsetY: 250,
  // Size of the node
  width: 100,
  height: 100,
  style: {
    fill: '#6BA5D7',
    strokeColor: 'white',
  },
  // Sets the annotation for the node
  annotations: [
    {
      // Sets the content for the annotation
      content: 'Annotation',
    },
  ],
};
// initialize Diagram component

var diagram = new ej.diagrams.Diagram(
  {
    width: '100%',
    height: '600px',
    nodes: [node],
  },
  '#element'
);

document.getElementById('updateOffset').onclick = () =>{
  diagram.nodes[0].annotations[0].offset = {x:0, y:0.5};
  //To reflect the changes instantly
  diagram.dataBind();
}
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Diagram</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-buttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-popups/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-splitbuttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-diagrams/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-navigations/styles/fabric.css" rel="stylesheet">
    
<script src="https://cdn.syncfusion.com/ej2/28.2.3/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <input type="button" value="updateOffset" id="updateOffset" />
        <div id="element"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

NOTE

Call dataBind() after property change to reflect the changes instantly.

The following table shows the position of annotation with different offsets.

offset	image
	Top Left {x:0,y:0}
	Middle left {x:0,y:0.5}
	Bootom left {x:0,y:1}
	Middle Top {x:0.5,y:0}
	Center {x:0.5,y:0.5}
	Middle Bottom {x:0.5,y:1}
	Top right {x:1,y:0}
	Middle right {x:1,y:0.5}
	Bottom right {x:1,y:1}

Annotation alignment

The horizontalAlignment property of annotation is used to set how the annotation is horizontally aligned at the annotation position determined from the fraction values. The verticalAlignment property is used to set how annotation is vertically aligned at the annotation position.

The following codes illustrates how to align annotations.

index.js
index.html
var node = {
    // Position of the node
    offsetX: 250,
    offsetY: 250,
    // Size of the node
    width: 100,
    height: 100,
    style: { fill: '#6BA5D7', strokeColor: 'white' },
    annotations: [{ content: 'Annotation',  horizontalAlignment: 'Left' , verticalAlignment: 'Top' }]
        };

// initialize Diagram component

var diagram = new ej.diagrams.Diagram({
    width: '100%', height: '600px', nodes: [node]
    }, '#element');
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Diagram</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-buttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-popups/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-splitbuttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-diagrams/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-navigations/styles/fabric.css" rel="stylesheet">
    
<script src="https://cdn.syncfusion.com/ej2/28.2.3/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <div id="element"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

The following tables illustrates all the possible alignments visually with ‘offset (0, 0)’.

Horizontal Alignment	Vertical Alignment	Output with Offset(0,0)
Left	Top
Center	Top
Right	Top
Left	Center
Center	Center
Right	Center
Left	Bottom
Center	Bottom
Right	Bottom

Update annotation alignment at runtime

Annotation alignment can be updated dynamically at runtime. The following code example shows how to update annotation alignment at runtim.

index.js
index.html
var node = {
  // Position of the node
  offsetX: 250,
  offsetY: 250,
  // Size of the node
  width: 100,
  height: 100,
  style: {
    fill: '#6BA5D7',
    strokeColor: 'white',
  },
  // Sets the annotation for the node
  annotations: [
    {
      // Sets the content for the annotation
      content: 'Annotation',
    },
  ],
};
// initialize Diagram component

var diagram = new ej.diagrams.Diagram(
  {
    width: '100%',
    height: '600px',
    nodes: [node],
  },
  '#element'
);

document.getElementById('updateAlign').onclick = () => {
  diagram.nodes[0].annotations[0].horizontalAlignment = 'Right';
  diagram.nodes[0].annotations[0].verticalAlignment = 'Bottom';
  //To reflect the changes instantly
  diagram.dataBind();
};
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Diagram</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-buttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-popups/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-splitbuttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-diagrams/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-navigations/styles/fabric.css" rel="stylesheet">
    
<script src="https://cdn.syncfusion.com/ej2/28.2.3/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <input type="button" value="updateAlign" id="updateAlign" />
        <div id="element"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>