Interaction in Angular Diagram component

27 Jun 202524 minutes to read

Selector

The selector visually represents selected elements, acting as a container to modify their size, position, and rotation angle interactively or programmatically. It supports selecting both single and multiple elements simultaneously.

Selection

An element can be selected by clicking that element. During single click, all previously selected items are cleared.

When selecting/unselecting the diagram elements, the selectionChange event and click gets triggered.
These events enable you to customize the selected elements as needed.

Selecting a group

When a child element of any group is clicked, its contained group is selected instead of the child element. With consecutive clicks on the selected element, selection is changed from top to bottom in the hierarchy of parent group to its children.

Multiple selection

Multiple elements can be selected with the following ways:

Ctrl+Click

During single click, any existing item in the selection list be cleared, and only the item clicked recently is there in the selection list. To avoid cleaning the old selected item, Ctrl key must be on hold when clicking.

Rubber band selection

Clicking and dragging in the diagram area allows you to create a rectangular region. The elements covered within this rectangular region will be selected when you release the mouse button.

In rubber band selection, you can set the selection of items by region using the following modes:

• CompleteIntersect: Selects items that are fully covered within the rectangular selection region.
• PartialIntersect: Selects items that are partially covered within the rectangular selection region.

This can be configured with the rubberBandSelectionMode.

Select/Unselect elements using API

The select and clearSelection methods are used to dynamically select or clear the selection of elements at runtime. The following code example demonstrates how these methods can be utilized to select or clear the selection of elements.

import { Component, ViewEncapsulation, ViewChild } from "@angular/core";
import { DiagramConstraints } from '@syncfusion/ej2-diagrams';
@Component({
  selector: "app-container",
  // specifies the template string for the diagram component
  template: `<ejs-diagram id="diagram" width="100%" height="900px" [nodes]='nodes'></ejs-diagram>`
})
export class AppComponent {
    @ViewChild("diagram")
    public diagramConstraints: DiagramConstraints;
    public nodes: NodeModel[] = [
        {
            id: 'node1',
            width: 90,
            height: 60,
            offsetX: 100,
            offsetY: 100,
            style: {
                fill:   '#6BA5D7',
                strokeColor: 'white',
                strokeWidth: 1
            },
        }
    ]
    ngOnInit(): void {
        //Select a specified collection of nodes and connectors in the diagram
        (this.diagram as any).select([this.diagram.nodes[0]]);
        //Removes all elements from the selection list, clearing the current selection.
        (this.diagram as any).clearSelection();
    }
}

Get selected items

You can get the currently selected nodes and connectors using selectedItems property of the diagram.

this.selectedNodes = this.diagram.selectedItems.nodes;
this.selectedConnectors = this.diagram.selectedItems.connectors;

You can also get the currently selected objects, both nodes and connectors, in a single array called selectedObjects within the selectedItems property of the diagram.

this.selectedObjects = this.diagram.selectedItems.selectedObjects;

Toggle selection

The canToggleSelection property determines whether the selection state of a diagram element should toggle with a mouse click at runtime. By default, this property is set to false. In the following example, the node can be selected with the first click and unselected with the second click.

app.component.ts

import {
  DiagramModule, DiagramComponent,
  NodeModel,
  ShapeStyleModel,
} from '@syncfusion/ej2-angular-diagrams';

import { Component, ViewEncapsulation, ViewChild } from '@angular/core';

@Component({
  imports: [DiagramModule],

  providers: [],
  standalone: true,
  selector: 'app-container',
  template: `<ejs-diagram #diagram id="diagram" width="100%" height="580px" [getNodeDefaults] ='getNodeDefaults' [nodes]='nodes' [selectedItems]='selectedItems'>
    </ejs-diagram>`,
  encapsulation: ViewEncapsulation.None,
})
export class AppComponent {
  @ViewChild('diagram')
  public diagram?: DiagramComponent;
  public nodes: NodeModel[] = [
    {
      id: 'node1',
      // Position of the node
      offsetX: 250,
      offsetY: 250,
      // Size of the node
      width: 100,
      height: 100,
      style: { fill: '#6BA5D7', strokeColor: 'white' },
    },
  ];
  public selectedItems: any = { canToggleSelection: true };
  public getNodeDefaults(node: NodeModel): NodeModel {
    node.height = 100;
    node.width = 100;
    return node;
  }
}

main.ts

import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));

Select entire elements in diagram programmatically

The selectAll method of diagram is used to select all the elements such as nodes/connectors in the diagram. Refer to the following code snippet.

//Selects all the nodes and connectors in diagram
this.diagram.selectAll();

You can also use the CTRL+A keys to select all nodes and connectors in the diagram.

Drag

You can drag an object by clicking and dragging it. When multiple elements are selected, dragging any one of them moves all selected elements together.
As you drag elements within the diagram, the positionChange event is triggered, providing opportunities to customize the dragged elements.

Resize

The selector in the diagram is designed with eight resizing handles, commonly referred to as thumbs. These handles allow users to adjust the size of selected items by clicking and dragging them. When resizing, dragging any handle modifies the dimensions of the selected elements accordingly. Notably, when dragging one corner handle, the opposite corner remains fixed to specific alignment of the selected item.

During the resizing process, the diagram triggers the sizeChange event, allowing customization based on the size of the element.

NOTE

While dragging and resizing, the objects are snapped towards the nearest objects to make better alignments.

Aspect ratio

Maintaining aspect ratio in diagram means that when you resize a node, by dragging its corner, both its width and height adjust proportionally. This ensures that the node retains its original shape and proportions. Aspect ratio constraints can be applied by configuring the NodeConstraints property.

app.component.ts

import {
  DiagramModule, NodeConstraints, DiagramComponent,
  NodeModel,
  ShapeStyleModel,
} from '@syncfusion/ej2-angular-diagrams';

import { Component, ViewEncapsulation, ViewChild } from '@angular/core';

@Component({
  imports: [DiagramModule],

  providers: [],
  standalone: true,
  selector: 'app-container',
  template: `<ejs-diagram #diagram id="diagram" width="100%" height="580px" [getNodeDefaults] ='getNodeDefaults' [nodes]='nodes'>
    </ejs-diagram>`,
  encapsulation: ViewEncapsulation.None,
})
export class AppComponent {
  @ViewChild('diagram')
  public diagram?: DiagramComponent;
  public nodes: NodeModel[] = [
    {
      id: 'node1',
      // Position of the node
      offsetX: 250,
      offsetY: 250,
      // Size of the node
      width: 100,
      height: 100,
      style: { fill: '#6BA5D7', strokeColor: 'white' },
      //Enables aspect ratio
      constraints:
        NodeConstraints.Default |
        NodeConstraints.AspectRatio,
    },
  ];
  public getNodeDefaults(node: NodeModel): NodeModel {
    node.height = 100;
    node.width = 100;
    return node;
  }
}

main.ts

import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));

Customizing resize-thumb size

You can change the size of the node resize thumb and the connector end point handle by using the handleSize property. The following example shows the resize handle size customization.

app.component.ts

import {
  DiagramModule, DiagramComponent,
  NodeModel,
  ShapeStyleModel,
} from '@syncfusion/ej2-angular-diagrams';

import { Component, ViewEncapsulation, ViewChild } from '@angular/core';

@Component({
  imports: [DiagramModule],

  providers: [],
  standalone: true,
  selector: 'app-container',
  template: `<ejs-diagram #diagram id="diagram" width="100%" height="580px" [getNodeDefaults] ='getNodeDefaults' [nodes]='nodes' [selectedItems]='selectedItems' (created)='create()'>
    </ejs-diagram>`,
  encapsulation: ViewEncapsulation.None,
})
export class AppComponent {
  @ViewChild('diagram')
  public diagram?: DiagramComponent;
  public create() {
    (this.diagram as DiagramComponent).select([(this.diagram as DiagramComponent).nodes[0]]);
  }
  public nodes: NodeModel[] = [
    {
      id: 'node1',
      // Position of the node
      offsetX: 250,
      offsetY: 250,
      // Size of the node
      width: 100,
      height: 100,
      style: { fill: '#6BA5D7', strokeColor: 'white' },
    },
  ];
  public selectedItems: any = { handleSize: 40 };
  public getNodeDefaults(node: NodeModel): NodeModel {
    node.height = 100;
    node.width = 100;
    return node;
  }
}

main.ts

import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));

The appearance such as fill, stroke, and stroke width of the node resize thumb and connector end point handle can be customized by overriding the e-diagram-resize-handle and e-diagram-endpoint-handle classes respectively.

Rotate

A rotation handler is positioned above the selector. Clicking and dragging this handler in a circular motion rotates the node. The node rotates around a fixed pivot point. A pivot thumb, located at the center of the node, appears during rotation to indicate the fixed point.
Rotating a node triggers the rotateChange event.

Customize rotate handle position

The position of the rotate handle can be adjusted by modifying the pivot point of the node using the pivot property. By default, the pivot point is set to (0.5, 0.5). The following example shows how to render the rotate handle at the left top corner of the node.

app.component.ts

import {
  DiagramModule, DiagramComponent,
  NodeModel,
  ShapeStyleModel,
} from '@syncfusion/ej2-angular-diagrams';

import { Component, ViewEncapsulation, ViewChild } from '@angular/core';

@Component({
  imports: [DiagramModule],

  providers: [],
  standalone: true,
  selector: 'app-container',
  template: `<ejs-diagram #diagram id="diagram" width="100%" height="580px" [getNodeDefaults] ='getNodeDefaults' [nodes]='nodes' (created)='create()'>
    </ejs-diagram>`,
  encapsulation: ViewEncapsulation.None,
})
export class AppComponent {
  @ViewChild('diagram')
  public diagram?: DiagramComponent;
  public create() {
    (this.diagram as DiagramComponent).select([(this.diagram as DiagramComponent).nodes[0]]);
  }
  public nodes: NodeModel[] = [
    {
      id: 'node1',
      // Position of the node
      offsetX: 250,
      offsetY: 250,
      // Size of the node
      width: 100,
      height: 100,
      style: { fill: '#6BA5D7', strokeColor: 'white' },
      //Pivot point
      pivot: { x: 0, y: 0 },
    },
  ];
  public getNodeDefaults(node: NodeModel): NodeModel {
    node.height = 100;
    node.width = 100;
    return node;
  }
}

main.ts

import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));

Connection editing

Each segment of a selected connector is editable with some specific handles/thumbs.

NOTE

For connector editing, you have to inject the ConnectorEditing module.

Drag connector end points

Source and target points of selected connectors are represented by two handles. Clicking and dragging these handles allows you to adjust the source and target points.

Dragging the connector end points triggers the following events for customization:

When the connector’s source point is changed, the sourcePointChange event is triggered.
When the connector’s target point is changed, the targetPointChange event is triggered.
Connecting a connector to port/node or disconnecting from them triggers the connectionChange event.

Straight segment editing

The end point of each straight segment is represented by a thumb that allows you to edit the segment. You can insert any number of new segments into a straight line by clicking while holding the Shift and Ctrl keys (Ctrl+Shift+Click).

Straight segments can be removed by clicking the segment end point while holding the Ctrl and Shift keys (Ctrl+Shift+Click).

Orthogonal segment editing

Orthogonal thumbs allow you to adjust the length of adjacent segments by clicking and dragging them. When necessary, segments are automatically added or removed during dragging to maintain proper orthogonal routing.

When editing a segment, the segmentChange event is triggered. When new segments are added to the collection of connector segments, the segmentCollectionChange event is triggered.

Bezier segment editing

Bezier segment thumbs allow you to adjust the segments by clicking and dragging them.

Bezier Control Points

Bezier segments are annotated with two thumbs representing the control points. These control points can be adjusted by clicking and dragging the control thumbs. Dragging the control point changes the angle and distance of the points from the segment point, modifying the curve.

Restrict Interaction in Negative Axis Area

The Diagram component includes a built-in option to restrict user interactions within the negative axis region—areas defined by negative X or Y coordinates. By enabling the RestrictNegativeAxisDragDrop constraint, the following interactions are prevented:

• Dragging: Diagram elements cannot be dragged into areas with negative coordinates.
• Resizing: The size of diagram objects cannot be adjusted to extend into the negative axis.
• Dropping Symbols: Symbols from the palette cannot be dropped in the negative region.

@Component({
  selector: "app-container",
  // specifies the template string for the diagram component with constraints
  template: `<ejs-diagram id="diagram" width="100%" height="580px" [constraints]='constraints'>
             </ejs-diagram>`
})
export class AppComponent {
// Prevent diagram interactions in the negative region
public constraints: DiagramConstraints = DiagramConstraints.Default |
                                         DiagramConstraints.RestrictNegativeAxisDragDrop
}

NOTE

A symbol dragged from the palette will only be added to the diagram if it’s fully positioned within the positive coordinate space.

User handles

User handles are used to add frequently used commands around the selector. To create user handles, define and add them to the userHandles collection of the selectedItems property. The name property of userHandles is used to define the name of the user handle, which can then be used at runtime for identification and customization.

The following events are triggered when interacting with a user handle:

• click - Triggered when the user handle is clicked.
• onUserHandleMouseEnter - Triggered when the mouse enters the user handle region.
• onUserHandleMouseDown - Triggered when the mouse is pressed down on the user handle.
• onUserHandleMouseUp - Triggered when the mouse is released on the user handle.
• onUserHandleMouseLeave - Triggered when the mouse leaves the user handle region.

Fixed user handle

Fixed user handles are used to perform specific actions when interacted with. Unlike regular user handles, fixedUserHandles are defined within the node/connector object, allowing different fixed user handles to be added to different nodes.

The following events are triggered when interacting with a fixed user handle:

• click - Triggered when the fixed user handle is clicked.
• onFixedUserHandleMouseEnter - Triggered when the mouse enters the fixed user handle region.
• onFixedUserHandleMouseDown - Triggered when the mouse is pressed down on the fixed user handle.
• onFixedUserHandleMouseUp - Triggered when the mouse is released on the fixed user handle.
• onFixedUserHandleMouseLeave - Triggered when the mouse leaves the fixed user handle region.
• fixedUserHandleClick - Triggered when the fixed user handle is clicked.

Determining Mouse Button Clicks

The diagram component can determine which mouse button was clicked. For example, when the right mouse button is clicked, the click event will specify that the right button was clicked. This is handled through the mouse click event, which provides details about whether the left or right button was clicked.

Notification	Description
Left	When the left mouse button is clicked, left is notified
Middle	When the mouse wheel is clicked, middle is notified
Right	When the right mouse button is clicked, right is notified

@Component({
    selector: "app-container",
    template: `<ejs-diagram id="diagram" width="100%" height="580px" (click)="click($event)"></ejs-diagram>`,
    encapsulation: ViewEncapsulation.None
})
export class AppComponent {
    ngOnInit(): void {
    }
    public click(args: IClickEventArgs): void {
    // Obtains the mouse button clicked
     var button = args.button
  }
}

Allow drop

The diagram supports dropping a node or connector onto another node or connector. To determine the target where the node or connector is dropped, you need to enable the allowDrop constraint in the node’s or connector’s constraints property. This setting enables a highlighter to indicate potential drop targets when dragging any node or connector over another one. Upon dropping the node or connector, the drop event is triggered to indicate which element was dropped over which other element.

Zoom pan

When loading a large diagram, only a certain portion of the diagram is initially visible, the remaining parts are clipped. You can explore these clipped portions by scrolling the scrollbars or panning the diagram. You can zoom in or out on the diagram by using Ctrl + mouse wheel. When the diagram is zoomed or panned, the scrollChange event is triggered.

Pan Status	Description
Start	When the mouse is clicked and dragged the status is notified as start.
Progress	When the mouse is in motion the status is notified as progress.
Completed	When panning is stopped the status is notified with completed.

Keyboard

Diagram provides support to interact with the elements with key gestures. By default, some in-built commands are bound with a relevant set of key combinations.

The following table illustrates those commands with the associated key values.

Shortcut Key	Command	Description
Ctrl + A	selectAll	Select all nodes/connectors in the diagram.
Ctrl + C	copy	Copy the diagram selected elements.
Ctrl + V	paste	Pastes the copied elements.
Ctrl + X	cut	Cuts the selected elements.
Ctrl + Z	undo	Reverses the last editing action performed on the diagram.
Ctrl + Y	redo	Restores the last editing action when no other actions have occurred since the last undo on the diagram.
Delete	delete	Deletes the selected elements.
Ctrl/Shift + Click on object		Multiple selection (Selector binds all selected nodes/connectors).
Up Arrow	nudge(“up”)	nudgeUp: Moves the selected elements towards up by one pixel.
Down Arrow	nudge(“down”)	nudgeDown: Moves the selected elements towards down by one pixel.
Left Arrow	nudge(“left”)	nudgeLeft: Moves the selected elements towards left by one pixel.
Right Arrow	nudge(“right”)	nudgeRight: Moves the selected elements towards right by one pixel.
Ctrl + MouseWheel	zoom	Zoom (Zoom in/Zoom out the diagram).
F2	startLabelEditing	Starts to edit the label of selected element.
Esc	endLabelEditing	Sets the label mode as view and stops editing.
Tab	Tab to Focus	Select the diagram element based on the rendering order when using the “Tab” key.
Shift + Tab	Go to Previous Object	This command is employed to shift the selection to the preceding object based on the z-order.
Control + B	Bold	Toggle bold formatting for the selected text.
Control + I	Italic	Toggle italic formatting for the selected text.
Control + U	Underline	Toggle underline formatting for the selected text.
Control + D	Duplicate	Duplicate a selected shape.
Control + G	Group	Group together multiple selected shapes, allowing them to be treated as a single shape.
Control + Shift + U	UnGroup	Ungroup shapes within a previously grouped selection.
Control + R	Rotate clockwise	Rotate the selected nodes in clockwise.
Control + L	Rotate anti-clockwise	Rotate the selected nodes in counterclockwise.
Control + H	Flip Horizontal	Flip the selected elements horizontally.
Control + J	Flip Vertical	Flip the selected elements vertically.
Control + 1	Pointer tool	Activate the pointer tool.
Control + 2	Text tool	Activate the text tool.
Control + 3	Connector tool	Activate the connector tool.
Control + 5	Freeform tool	Activate the freeform tool.
Control + 6	Line tool	Activate the polyline tool.
Control + +	Zoom In	Zoom in the diagram.
Control + -	Zoom Out	Zoom out the diagram.
Shift + Up Arrow	Up	Moves the selected elements towards up by 5 pixel.
Shift + Down Arrow	Down	Moves the selected elements towards down by 5 pixel.
Shift + Left Arrow	Left	Moves the selected elements towards left by 5 pixel.
Shift + Right Arrow	Right	Moves the selected elements towards right by 5 pixel.
Control + Shift + L	Align Text Left	Align the selected text to the left.
Control + Shift + C	Center Text Horizontally	Center the selected text horizontally.
Control + Shift + R	Align Text Right	Align the selected text to the right.
Control + Shift + J	Justify Text Horizontally	Justify the selected text, aligning it to both the left and right margins.
Control + Shift + E	Top-align Text Vertically	Align the selected text to the top vertically.
Control + Shift + M	Center Text Vertically	Center the selected text vertically.
Control + Shift + V	Bottom-align Text Vertically	Align the selected text to the bottom vertically.
Control + Shift + B	Send To Back	Send the selected shape backward in the stacking order, making it appear behind other shapes.
Control + Shift + F	Bring To Front	Bring the selected shape forward in the stacking order, making it appear in front of other shapes.
Control + [	Send Backward	Move the selected shape one step backward in the layer order.
Control + ]	Bring Forward	Move the selected shape one step forward in the layer order.

NOTE

Please note that the positionChange event is triggered for dragging nodes/connectors using mouse interactions only and not supported for Keyboard interactions

See Also

• How to create diagram nodes using drawing tools
• How to create diagram connectors using drawing tools
• How to disable the diagram interaction
• How to control the diagram history
• How to create overview control to the diagram