Label
19 Jul 201724 minutes to read
Label is a block of text that can be displayed over a node or connector. Label is used to textually represent an object with a string that can be edited at run time. You can add Multiple Labels to a node/connector.
Create Label
You can add a label to a node/connector by defining the label object and adding that to the labels collection of node/connector. The text property of label defines the text to be displayed. The following code illustrates how to create a Label.
<div>
<ej-diagram id="diagramCore" width="100%" height="500px" [nodes]="nodes" [connectors]="connectors">
</ej-diagram>
</div>import { Component } from '@angular/core';
@Component({
selector: 'ej-app',
templateUrl: 'app/components/diagram/default.component.html'
})
export class ShapesComponent {
nodes: Array<any>;
connectors: Array<any>;
constructor() {
this.nodes = [
{
name: "node",
offsetX: 100,
offsetY: 100,
width: 100,
height: 50,
borderColor: "black",
fillColor: "#1BA0E2",
//Initializes labels collection
labels: [
// Defines JSON to create a label
{
//Defines the text to be displayed
text: "Label"
}
]
}
];
this.connectors = [{
name: "connector1",
sourcePoint: {
x: 200,
y: 50
},
targetPoint: {
x: 300,
y: 150
},
segments: [{
type: "orthogonal",
length: 50,
direction: "bottom"
}],
//Initializes labels collection
labels: [
//Defines JSON to create a label
{
//Defines the text to be displayed
text: "Label",
//Defines the background color of the text block
fillColor: "white"
}
]
}];
}
}
To explore more label properties, refer to Label Properties.
Add Labels at runtime
Labels can be added at runtime by using the client side method addLabel. The following code illustrates how to add a label to a node.
var diagram = $("#sourceDiagram").ejDiagram("instance");
// Defines JSON to create a label
var label = {
name: "label",
text: "Node"
};
diagram.addLabel("node1", label);
//Insert label at a specific index of labels collection
var label = {
name: "label",
text: "New Label",
offset: {
x: 0.1,
y: 0.1
}
};
diagram.insertLabel("node1", label, 1);
Update Label at runtime
The client side API updateLabel is used to update the labels at run time.
The following code example illustrates how to change the label properties.
var diagram = $("#diagram").ejDiagram("instance");
var selectedObject = diagram.model.selectedItems.children[0];
diagram.updateLabel(selectedObject.name, selectedObject.labels[0], {
text: "label",
fillColor: "red"
});Alignment
Label can be aligned relative to the node boundaries. It has margin, offset, horizontal and vertical alignment settings. It is quite tricky when all four alignments are used together but gives you more control over alignment.
Offset
The offset property of label is used to align the labels based on fractions. 0 represents top/left corner, 1 represents bottom/right corner, and 0.5 represents half of width/height.
The following image shows the relationship between the label position (black colored circle) and offset (fraction values).
Horizontal and vertical alignments
The horizontalAlignment property of label is used to set how the label is horizontally aligned at the label position determined from the fraction values. The verticalAlignment property is used to set how label is vertically aligned at the label position.
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 |  |
|
| Right |  |
|
| Left | Center |  |
| Center |  |
|
| Right |  |
|
| Left | Bottom |  |
| Center |  |
|
| Right |  |
The following codes illustrates how to align labels.
import { Component } from '@angular/core';
@Component({
selector: 'ej-app',
templateUrl: 'app/components/diagram/default.component.html'
})
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [
{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
labels: [{
text: "Label",
// Sets offset to label
offset: {
x: 0,
y: 0.5
},
// Sets to align label horizontally relative to given offset
horizontalAlignment: ej.datavisualization.Diagram.HorizontalAlignment.Left,
// Sets to align label vertically relative to given offset
verticalAlignment: ej.datavisualization.Diagram.VerticalAlignment.Center,
// Sets text alignment to label
textAlign: ej.datavisualization.Diagram.TextAlign.Center
}]
}
];
}
}
Label alignment with respect to Segments
segmentOffset and alignment properties of label allows you to align the connector labels with respect to the segments. In the following image, the labels are placed exactly over the segments regardless of its rectangular bounds.
Following code example illustrates how to align connector labels.
<div>
<ej-diagram id="diagramCore" width="100%" height="490px" [nodes]="nodes"
[connectors]="connectors" [defaultSettings]="defaultSettings">
</ej-diagram>
</div>import {Component} from '@angular/core';
@Component({
selector: 'ej-app',
templateUrl: 'app/components/diagram/umldiagram.component.html',
})
export class UMLDiagramComponent {
nodes: Array<any>;
connectors: Array<any>;
defaultSettings: Object;
constructor() {
this.nodes = [
{
name: "node1",
width: 50,
height: 40,
offsetX: 200,
offsetY: 200,
labels: [{
"text": "Task 1"
}]
},
{
name: "node2",
width: 50,
height: 40,
offsetX: 400,
offsetY: 200,
labels: [{
"text": "Task 2"
}]
}
];
this.connectors = [
{
name: "connector1",
sourceNode: "node1",
targetNode: "node2"
}];
this.defaultSettings = {
connector: {
segments: [{
type: "orthogonal"
}],
// Sets labels for segments
labels: [{
text: "0",
fontColor: "black",
// Aligns the label either top or left(before) of the connector segment
alignment: "before",
// Sets the position of the label with respect to the segment
segmentOffset: 0
}, {
text: "1",
fontColor: "black",
// Aligns the label either bottom or right(after) of the connector segment
alignment: "after",
// Sets segmentOffset as 1
segmentOffset: 1,
// Enables boundaryConstraints for the label should be docked within the label bounds
boundaryConstraints: true,
}],
lineWidth: 2
},
node: {
borderColor: "#000000",
fillColor: "#1BA0E2",
labels: [{
"fontColor": "black",
}]
}
};
}
}
By default, connector labels will be aligned with respect to the segments. The relativeMode property of label allows you to disable this segment specific label alignment. Following code example illustrates how to disable the segment specific label alignment.
export class ShapesComponent {
nodes: Array<any>;
connectors: Array<any>;
constructor() {
this.nodes = [
{
name: "node1",
width: 50,
height: 40,
offsetX: 200,
offsetY: 200,
labels: [{
"text": "Task 1"
}]
}.
{
name: "node2",
width: 50,
height: 40,
offsetX: 400,
offsetY: 200,
labels: [{
"text": "Task 2"
}]
}
];
this.connectors = [{
name: "connector1",
sourceNode: "node1",
targetNode: "node2",
lineWidth: 2,
segments: [{
type: "orthogonal"
}],
// Sets labels for segments
labels: [{
text: "0",
fontColor: "black",
//Sets the relativeMode as segmentpath
relativeMode: "segmentpath",
}]
}]
}
}Margin
Margin is an absolute value used to add some blank space in any one of its four sides. You can displace the labels with the margin property.
The following code example illustrates how to align a label based on its offset, horizontalAlignment, verticalAlignment and margin values.
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
labels: [{
text: "Label",
offset: {
x: 0.5,
y: 1
},
horizontalAlignment: ej.datavisualization.Diagram.HorizontalAlignment.Center,
verticalAlignment: ej.datavisualization.Diagram.VerticalAlignment.Top,
//Sets margin to add label outside a node
margin: {
top: 10
}
}]
}];
}
}
Text Alignment
The textAlign property of label allows you to set how the text should be aligned (left, right, center, or justify) inside the text block. The following codes illustrate how to set textAlign for a label.
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
// Sets text alignment for a label
labels: [{
text: "Text Align is set as Left",
textAlign: ej.datavisualization.Diagram.TextAlign.Left
}]
}];
}
}
| TextAlign | Image |
|---|---|
| Left |  |
| Right |  |
| Center |  |
| Justify |  |
Wrapping
When text overflows node boundaries, you can control it by using text wrapping. So, it is wrapped into multiple lines. The wrapping property of label defines how the text should be wrapped. The following code illustrates how to wrap a text in a node.
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
//Enables Text-wrapping
labels: [{
text: "Label Text Wrapping",
wrapping: ej.datavisualization.Diagram.TextWrapping.Wrap
}]
}];
}
}
| Values | Description | Image |
|---|---|---|
| NoWrap | Text will not be wrapped |  |
| Wrap | Text-wrapping occurs when the text overflows beyond the available node width. |  |
| WrapWithOverflow (Default) | Text-wrapping occurs when the text overflows beyond the available node width. However, the text may overflow beyond the node width in the case of a very long word. |  |
Appearance
You can change the font style of the labels with the font specific properties(fontSize,fontFamily,fontColor.,). The following code illustrates how to customize the appearance of a label.
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
labels: [{
text: "Label Text",
//Sets styles to a label
fontSize: 12,
fontFamily: "TimesNewRoman",
fontColor: "black",
bold: true,
italic: true,
textDecoration: ej.datavisualization.Diagram.TextDecorations.Underline
}]
}];
}
}
The fill, border and opacity appearances of the text can also be customized with appearance specific properties of label.The following code illustrates how to customize background, opacity and border of a label.
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
labels: [{
text: "Label Text",
//Customizes background and borders of a label
fillColor: "white",
borderColor: "black",
borderWidth: 1,
//Customize transparency of a label
opacity: 0.7
}]
}];
}
}
Drag
A Label can be displaced from its original position to any preferred location interactively. Dragging is disabled by default. You can enable label dragging with the constraints property of node/connector. The following code illustrates how to enable label dragging.
export class ShapesComponent {
nodes: Array<any>;
connectors: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
//Enables Label Dragging for node.
constraints: ej.datavisualization.Diagram.NodeConstraints.Default | ej.datavisualization.Diagram.NodeConstraints.DragLabel,
labels: [{
text: "Text Align is set as Left",
}]
}];
this.connectors = [{
name: "connector1",
sourcePoint: {
x: 200,
y: 50
},
targetPoint: {
x: 300,
y: 150
},
segments: [{
type: "orthogonal",
length: 50,
direction: "bottom"
}],
//Enables Label Dragging for connector.
constraints: ej.datavisualization.Diagram.ConnectorConstraints.Default | ej.datavisualization.Diagram.ConnectorConstraints.DragLabel,
labels: [{
text: "Label "
}]
}];
}
}
Rotate
You can rotate the labels to any desired angle. Labels are rotated to the angle that is defined by the rotateAngle property of label. The following code illustrates how to rotate a label.
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
labels: [{
text: "Label",
//Sets label's rotation Angle
rotateAngle: 45
}]
}];
}
}
NOTE
There is no built-in support to rotate labels interactively.
Edit
Diagram provides support to edit a Label at runtime, either programmatically or interactively. By default, label is in View mode. But it can be brought to edit mode in two ways;
- By double-clicking the label.
- By selecting the item and pressing the F2 key.
Double-clicking any label will enables editing of that. Double-clicking the node enables first label editing. When the focus of editor is lost, the label for the node is updated.
You can programmatically edit the label by changing the mode of the label. The following code illustrates how to edit the label programmatically.
var diagram = $("#diagram").ejDiagram("instance");
var node = diagram.model.selectedItems.children[0];
//Sets label mode as Edit
var options = {
mode: ej.datavisualization.Diagram.LabelEditMode.Edit
};
diagram.updateLabel(node.name, node.labels[0], options);
Read Only labels
Diagram allows to create read only labels. You have to set the readOnly property of label to enable/disable the read only mode. The following code illustrates how to enable readOnly mode.
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
//Sets label as read-only
labels: [{
text: "Label",
readOnly: true
}]
}];
}
}Multiple labels
You can add any number of labels to a node or connector. The following code illustrates how to add multiple labels to a node.
export class ShapesComponent {
nodes: Array<any>;
constructor() {
this.nodes = [{
name: "node",
width: 100,
height: 100,
offsetX: 100,
offsetY: 100,
borderColor: "black",
fillColor: "#1BA0E2",
//Adds multiple labels to a node
labels: [{
text: "Left",
offset: {
x: 0.12,
y: 0.1
}
}, {
text: "Center",
offset: {
x: 0.5,
y: 0.5
}
}, {
text: "Right",
offset: {
x: 0.82,
y: 0.9
}
}]
}];
}
}
Limitation
- To enable faster rendering, labels are rendered in a separate layer because of this, all the labels always stay on top. When two nodes are overlapped, text of underlying node is not hidden by the overlapped node.
| Expected behavior | Current behavior |
|---|---|
 |
 |