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History List

Diagram tracks the history of actions that are performed after initializing the diagram and provides support to reverse and restore those changes.

Undo and redo

Diagram provides built-in support to track the changes that are made through interaction and through public APIs. The changes can be reverted or restored either through shortcut keys or through commands.

Note: If you want to use Undo-Redo in diagram, you need to inject UndoRedo in the diagram.

Undo/redo through shortcut keys

Undo/redo commands can be executed through shortcut keys. Shortcut key for undo is Ctrl+z and shortcut key for redo is Ctrl+y.

Undo/redo through public APIs

The client-side methods undo and redo help you to revert/restore the changes.

The following code example illustrates how to undo/redo the changes through script.

// initialize Diagram component
let diagramInstance: DiagramComponent;
ReactDOM.render( < DiagramComponent id = "diagram" ref={diagram => diagramInstance = diagram}
    width = {
        '100%'
    }
    height = {
        '600px'
    }
    // Add node
    nodes = []
    // render initialized Diagram
    /> , document.getElementById("diagram"));

// Reverts the last action performed
diagramInstance.undo();

// Restores the last undone action
diagramInstance.redo();

When a change in the diagram is reverted or restored (undo/redo), the historyChange event gets triggered.

Group multiple changes

History list allows to revert or restore multiple changes through a single undo/redo command. For example, revert/restore the fill color change of multiple elements at a time.

The client-side method startGroupAction is used to notify the diagram to start grouping the changes. The client-side method endGroupAction is used to notify to stop grouping the changes. The following code illustrates how to undo/redo fillColor change of multiple elements at a time.

Source
Preview
index.tsx
import * as React from "react";
import * as ReactDOM from "react-dom";
import {
    Diagram,
    NodeModel,
    DiagramComponent,
    ConnectorModel,
    UndoRedo,
    Inject
} from "@syncfusion/ej2-react-diagrams";

let diagramInstance: DiagramComponent;
let nodes: NodeModel[] = [{
    id: 'Start',
    width: 140,
    height: 50,
    offsetX: 300,
    offsetY: 50,
    annotations: [{
        id: 'label1',
        content: 'Start'
    }],
    shape: {
        type: 'Flow',
        shape: 'Terminator'
    }
}];
ReactDOM.render( <DiagramComponent id = "diagram" ref={diagram => (diagramInstance = diagram)}
        width = {
            '100%'
        }
        height = {
            '600px'
        }
        nodes = {
            nodes
        }
        created = {
            () => {
                //Start to group the changes
                diagramInstance.startGroupAction();
                //Makes the changes
                let color: string[] = ['black', 'red', 'green', 'yellow']
                for (var i = 0; i < color.length; i++) {
                    // Updates the fillColor for all the child elements.
                    diagramInstance.nodes[0].style.fill = color[i];
                    diagramInstance.dataBind();
                }
                //Ends grouping the changes
                diagramInstance.endGroupAction();
            }
        }
        getNodeDefaults = {
            (node: NodeModel) => {
                node.height =  100;
                node.width =  100;
                node.style.fill =  '#6BA5D7';
                node.style.strokeColor =  'white';
                return  node;
            }
        }
        ><Inject services={[UndoRedo]}/>
        </DiagramComponent>,   document.getElementById("diagram") );

Track custom changes

Diagram provides options to track the changes that are made to custom properties. For example, in case of an employee relationship diagram, track the changes in the employee information. The historyList of the diagram enables you to track such changes. The following example illustrates how to track such custom property changes.

Before changing the employee information, save the existing information to historyList by using the client-side method push of historyList. The historyList canLog method can be used which takes a history entry as argument and returns whether the specific entry can be added or not.

The following code example illustrates how to save the existing property values.

let diagramInstance: DiagramComponent;
ReactDOM.render( < DiagramComponent id = "diagram" ref={diagram => diagramInstance = diagram}
        width = {
            '100%'
        }
        height = {
            '600px'
        }
        />,   document.getElementById("diagram") );

        //Creates a custom entry
        let entry: HistoryEntry = {
            undoObject: diagramInstance.nodes[0];
        };
        // adds that to history list
        diagramInstance.historyList.push(entry);
        diagramInstance.dataBind();

canLog

canLog in the history list, which takes a history entry as argument and returns whether the specific entry can be added or not.

Source
Preview
index.tsx
import * as React from "react";
import * as ReactDOM from "react-dom";
import {
    Diagram,
    DiagramComponent,
    NodeModel,
    ConnectorModel,
    UndoRedo,
    Inject
} from "@syncfusion/ej2-react-diagrams";
let diagramInstance: DiagramComponent;
let nodes: NodeModel[] = [{
    id: 'Start',
    width: 140,
    height: 50,
    offsetX: 300,
    offsetY: 50,
    annotations: [{
        id: 'label1',
        content: 'Start'
    }],
    shape: {
        type: 'Flow',
        shape: 'Terminator'
    }
}];
ReactDOM.render( <DiagramComponent id = "diagram" ref={diagram => (diagramInstance = diagram)}
        width = {
            '100%'
        }
        height = {
            '600px'
        }
        nodes = {
            nodes
        }
        created = {
            () => {
                // canLog decide whether the entry add or not in history List
                diagramInstance.historyList.canLog = function(entry: HistoryEntry) {
                entry.cancel = true;
                return entry;
                }
            }
        }

        getNodeDefaults = {
            (node: NodeModel) => {
                node.height =  100;
                node.width =  100;
                node.style.fill =  '#6BA5D7';
                node.style.strokeColor =  'white';
                return  node;
            }
        }
        ><Inject services={[UndoRedo]}/>
        </DiagramComponent>,   document.getElementById("diagram") );

Track undo/redo actions

The historyList undoStack property is used to get the collection of undo actions which should be performed in the diagram. The undoStack/redoStack is the read-only property.

let diagramInstance: DiagramComponent;
ReactDOM.render( < DiagramComponent id = "diagram" ref={diagram => diagramInstance = diagram}
width = {
    '100%'
}
height = {
    '600px'
}
nodes = {
    nodes
}
/>,   document.getElementById("diagram") );

//get the collection of undoStack objects
let undoStack = diagramInstance.historyList.undoStack;
//get the collection of redoStack objects
let redoStack = diagramInstance.historyList.redoStack;

History change event

The historychange event triggers, whenever the interaction of the node and connector is take place.

let diagramInstance: DiagramComponent;
ReactDOM.render( < DiagramComponent id = "diagram" ref={diagram => diagramInstance = diagram}
        width = {
            '100%'
        }
        height = {
            '600px'
        }
        nodes = {
            nodes
        }
        />,   document.getElementById("diagram") );
        // history change event
        diagramInstance.historyChange = (arg: IHistoryChangeArgs) => {
            //causes of history change
            let cause: string = arg.cause;
        }