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Connecting shapes

Edges in a Diagram represent the relationships between nodes and groups. They are highly configurable, supporting various connector types, overlays (like arrows), and markers.

Configuration​

You configure the default behavior and appearance of edges in a Diagram using the edges section of the DiagramOptions interface.

const diagramOptions = {
  // ... other options
  edges: {
    anchor: "AutoDefault",          // Default anchor for edges
    connector: {                    // Default connector type and options
        type: "Orthogonal",
        options: {
            cornerRadius: 3
        }
    },
    editable: true,                 // Whether edges can be edited via the UI
    avoidVertices: true,            // Whether edges should avoid overlapping vertices
    allowUnattached: true,          // Whether edges can exist without being connected to a target
    propertyMappings: []       // Mappings to drive edge appearance from data
  }
}

Options​

The edges section supports the following options:

NameTypeDescription
anchorAnchorSpecThe default anchor(s) to use for edges.
connectorConnectorSpecThe default connector type (e.g., "Orthogonal", "Bezier", "Straight") and its options.
editablebooleanWhether edges are editable by the user. Defaults to true.
avoidVerticesbooleanIf true, the connector will attempt to route around vertices.
allowUnattachedbooleanIf true, users can drag an edge that isn't connected to a target vertex.
propertyMappingsEdgePropertyMappingsA set of mappings that define how edge data affects its appearance.
colorstringDefault color for the edges.
outlineWidthnumberDefault width for the edge lines.

Linking from Diagram tools​

When a vertex (node or group) is selected in a Diagram, a set of tools appears around it. One of these tools is the Link tool (usually represented by a chain icon or a plus icon with an arrow).

Dragging from this tool allows users to create a new edge. You can control whether this tool is available for a specific vertex using the canLink method in the Diagram Mediator.

Connectors​

Connectors define the path that an edge takes between its source and target.

Connectors are the lines that actually join elements of the UI. They are the visual representation of edges. VisuallyJs has four connector types:

  • Bezier - a Bezier curve with two control points
  • Straight - One or more straight line segments, optionally smoothed or with rounded corners
  • Orthogonal - Horizontal/vertical straight line segments, optionally with rounded corners
  • QuadraticBezier - a Bezier curve with a single control point
info

The default, if you do not provide a value, is to use the Straight connector.

Overlays and Markers​

Overlays are UI elements attached to an edge, such as arrows, labels, or custom shapes. Markers are specific types of overlays that appear at the start or end of an edge.

In Diagrams, you typically use propertyMappings to define which overlays or markers should be visible based on the edge's data.

Unattached Edges​

By default, edges in a Diagram must be connected to both a source and a target, but unattached edges are supported and can be enabled. You can toggle this behavior using the allowUnattached option.

When allowUnattached is set to true, users can drag either end of an edge off a shape and leave it in whitespace. This is useful for creating diagrams where some connections might be incomplete or for visually indicating flow that doesn't yet have a target.

Edge Geometry and Editors​

When editable is set to true in the edges configuration, users can modify the path of an edge. VisuallyJs automatically selects the appropriate editor based on the connector type.

VisuallyJs supports editing the path of edges for each of the different connector types that VisuallyJs ships with. The selection of the appropriate editor tool is managed automatically by VisuallyJs.

Setup​

In a diagram, edge path editing is enabled by default (as long as the diagram is not marked editable:false). If you want to disable path editing, without marking the diagram readonly, you need to set the editable flag in the edges section of your render options:

Path editing begins when the user taps on an edge, and stays active until they click on whitespace, or perform some other operation such as editing a cell,

Each editor offers a different interface for working with path edits.

Orthogonal editors​

The orthogonal editor draws a handle on each segment of an edge, which can be dragged at 90 degrees to the direction of travel of the segment, ie. for a vertical segment, you can shift it horizontally, and for a horizontal segment you can shift it vertically.

When you are shifting a segment, if you release the mouse at such a point that the segment you just dragged forms a straight line with a previous or subsequent segment, the segments are coalesced into one. If you drag some segment such that an existing segment ceases to be a straight line, the segment is split and new segment is inserted between them.

Static anchors​

In this example we use an edge editor to edit the path of some edge whose anchors are at fixed points (in this case, AnchorLocations.Bottom and AnchorLocations.Top). We've also already called startEditingPath(..) on the surface for you:

Dynamic anchors​

If the edge you are editing has dynamic anchors, the edge editor will draw a placeholder at each end of the edge, which you can drag around to any supported position for the given anchor - here we use the AutoDefault dynamic anchor, which is an anchor that has one position on each of the four sides of the element on which it resides:

When you start to drag an anchor placeholder, you'll see VisuallyJs adds an element indicating an allowed position to which that anchor can be moved.

Continuous anchors​

If your edge is using anchor of type AnchorLocations.Continuous (which is the default), when you drag an anchor placeholder VisuallyJs will highlight the candidate face for the anchor relocation:

Avoiding vertices​

By default, the orthogonal connector editor will avoid getting into a situation where either end of the connector intersects the source or target vertex. This is best illustrated with a picture:

Orthogonal connector avoiding vertices - VisuallyJs - industry standard diagramming and rich visual UI Javascript and Typescript library

info

This functionality is only applied to the segments at either end of a connector. If you have some connector path that intersects the source or target vertex somewhere in the middle of the path, the path will not be re-routed to avoid the vertex.

If you want to switch this behaviour off, you can do so in the connector spec:

connector:{
    type:"Orthogonal",
    options:{
        vertexAvoidance:false
    }
}

This will be the resulting behaviour:

Orthogonal connector intersecting vertices - VisuallyJs - flowcharts, AI Agent builders, chatbots, bar charts, decision trees, mindmaps, org charts and more

Your users can still route the connector around in this setup but they'll have to move a lot more segments.

Straight editors​

The straight editor draws a handle at the end of each segment of an edge, which can be dragged in any direction to alter its location. You can split a segment by clicking and holding the mouse at the location you wish to split the segment, and then dragging the new handle.

To delete a handle, click on it.

Static anchors​

In this example we use an edge editor to edit the path of some edge whose anchors are at fixed points (in this case, AnchorLocations.Right and AnchorLocations.Top). We've also already called startEditingPath(..) for you:

Dynamic anchors​

If the edge you are editing has dynamic anchors, the edge editor will draw a placeholder at each end of the edge, which you can drag around to any supported position for the given anchor - here we use the AutoDefault dynamic anchor, which is an anchor that has one position on each of the four sides of the element on which it resides:

When you start to drag an anchor placeholder, you'll see VisuallyJs adds an element indicating an allowed position to which that anchor can be moved.

Continuous anchors​

If your edge is using anchor of type AnchorLocations.Continuous, when you drag an anchor placeholder VisuallyJs will highlight the candidate face for the anchor relocation:

Smoothed connectors​

When you have smooth:true set on your connector, the editor functions slightly differently - the drag handles now represent the location of the control points for the splines that make up the Bezier curve, and when you drag them, the control points are moved accordingly. Also when smooth is set, the editor draws a guideline for each segment.

Bezier editors​

The bezier editor draws two handles - one for each control point in the connector. They are placed where the control point is, and as you drag them around the control points are updated accordingly.

Static anchors​

In this example we use an edge editor to edit the path of some edge whose anchors are at fixed points (in this case, AnchorLocations.Bottom and AnchorLocations.Top). We've also already called startEditingPath(..) on the surface for you:

QuadraticBezier editors​

The QuadraticBezier editor draws one handle, located at the connector's control point. As you drag the handle around, the connector's control point is updated.

Overlays​

You can supply a set of overlays to render on an edge for the duration of the edit, for example:


diagram.startEditingPath(someEdge, {
  overlays:[
    {
      type:LabelOverlay.type,
      options:{
        label:"editing...",
        location:0.1
      }
    }    
  ]
})

With this call we get a label overlay at location 0.1:

Delete button​

The edge path editor offers a shortcut method to attach a delete button:

diagram.startEditingPath(someEdge, {
  deleteButton:true
})

This results in:

This will delete the edge without prompting the user. If you'd like to hook into the edge deletion, you can provide an onMaybeDelete function.

diagram.selectEdge(someEdge, {
  deleteButton:true,
  onMaybeDelete:(edge, connection, doDelete) => {
      if (confirm(`Delete edge ${edge.id}`)) {
          doDelete()
      }
  }
})

Note that the operation is asynchronous - in the example above we use the windows prompt method, but you can invoke the doDelete callback at any stage.

Clearing path edits​

Edits made to a path can be cleared via clearPathEdits method on the Diagram object.

clearPathEdits (edgeOrLink:Edge|DiagramLink):boolean

Edge Geometry​

The geometry of an edge is stored in its backing data when it has been edited or when vertex avoidance is active. This geometry consists of the anchor positions and any intermediate segments or control points.

Edge Mappings​

Edge mappings are a powerful way to drive the visual representation of an edge (its style, overlays, and markers) from the properties in its backing data.

Property mapping allows you to match specific values for a given property/properties to a set of config options - it's related to the concept of UI States, but it's a "pull" rather than "push": when you update the model, the UI figures out what config to apply for a given object, rather than you having to tell it.

note

This functionality is available only for edges. We are investigating options for how this could be usefully extended to nodes, groups and ports.

Example​

This example is drawn from the Flowchart starter app's source code:


import { ArrowOverlay } from "@visuallyjs/browser-ui"

const ARROW_WIDTH = 5
const ARROW_LENGTH = 10
const CLASS_DASHED_EDGE = "some-css-class"

const PROPERTY_LINE_STYLE = "lineStyle"

const EDGE_TYPE_SOURCE_ARROW = "source"
const EDGE_TYPE_TARGET_ARROW = "target"
const EDGE_TYPE_PLAIN = "plain"
const EDGE_TYPE_DASHED = "dashed"

const edgeMappings = [
    {
        property:PROPERTY_LINE_STYLE,
        mappings:{
            [EDGE_TYPE_SOURCE_ARROW]:{
                overlays:[
                    {
                        type:ArrowOverlay.type,
                        options:{
                            location:0,
                            direction:-1,
                            width:ARROW_WIDTH,
                            Length:ARROW_LENGTH
                        }
                    } ]
            },
            [EDGE_TYPE_TARGET_ARROW]:{
                overlays:[
                    {
                        type:ArrowOverlay.type,
                        options:{
                            location:1,
                            width:ARROW_WIDTH,
                            length:ARROW_LENGTH
                        }
                    }
                ]
            },
            [EDGE_TYPE_PLAIN]:{},
            [EDGE_TYPE_DASHED]:{
                cssClass:CLASS_DASHED_EDGE
            }
        }
    }
]

Each mapping consists of a property name (or list of names - see below) and a map of values to configs (the specific type of these configs is EdgeMapping). Here we have declared a set of mappings for the property lineStyle in the backing data for an edge:

{
    property:PROPERTY_LINE_STYLE,
    mappings: {
        [EDGE_TYPE_SOURCE_ARROW] : {
        ...
        }
    ...
    }
}

So if you had an edge with this definition:

{
  source: "1",
  target: "2",
  data:{
      lineStyle:"source"
  }
}

Then the corresponding connection would have an Arrow overlay at location 0.

Updating data​

When an edge is updated, the property mappings are inspected. Any that are no longer valid are removed, and any that are now valid are added:

model.updateEdge(someEdge, {
    lineStyle:EDGE_TYPE_DASHED
})

This would result in the arrow overlay being removed, and "some-css-class" being added to the connection's class list, because there is a mapping for EDGE_TYPE_DASHED:

mappings:{
    
    ... 
    
    [EDGE_TYPE_DASHED]:{
        cssClass:CLASS_DASHED_EDGE
    }
}

Wildcard mappings​

You can use "*" or WILDCARD from @visuallyjs/browser-ui as the value for some property, which will instruct the UI that the given config should be applied regardless of the value of the mapped property (as long as it is present, not null):

import { WILDCARD } from "@visuallyjs/browser-ui"

{
    property:"label",
    mappings:{
        [WILDCARD]:{
            overlays:[
                {
                    type:LabelOverlay.type,
                    options:{
                        label:"{{label}}",
                        location:0.5,
                        cssClass:"some-label"
                    }
                }
            ]
        }
    }
}

Here, we have instructed VisuallyJs to show a label whenever an edge's backing data has a label property. Incidentally, this specific requirement can actually be neatly handled by Edge labels.

Multiple properties​

You can map multiple properties instead of just a single property if you need the extra flexibility. For example, these are property mappings for an edge in a conceptual ERD, in which edges between entities and relationships show cardinality, but only at one end. We can model that with two properties:

propertyMappings: [
    {
        property: ["cardinality", "terminus"],
        mappings:{
            "one source": {
                sourceMarker: OneOverlay.type
            },
            "one target": {
                targetMarker: OneOverlay.type
            }
        }
    }
]

Then in our dataset we might have edges like this:

[
    { source:"1", target:"2", data:{ cardinality:"one", terminus:"source" }},
    { source:"2", target:"3", data:{ cardinality:"many", terminus:"target" }}
]

The important point to note in the example mapping above is that the order of the keys must be reflected in the mapping keys: we declare ["cardiinality", "terminus"] as our properties, and our mapping keys are "one source" and "one target", ie. the values to match are in the same order as the property keys.

Examples​

Flowchart Starter App​

In the Flowchart starter app, edge mappings are used to switch between different arrow configurations and line styles (plain or dashed).

export default function edgeMappings(): EdgePropertyMappings {
    return [
        {
            property: "lineStyle",
            mappings: {
                "plain": { },
                "dashed": {
                    dashArray: "2"
                }
            }
        },
        {
            property: "markers",
            mappings: {
                "source": {
                    overlays: [
                        { type: ArrowOverlay.type, options: { location: 0, direction: -1 } }
                    ]
                },
                "target": {
                    overlays: [
                        { type: ArrowOverlay.type, options: { location: 1 } }
                    ]
                }
            }
        }
    ]
}

BPMN Starter App​

The BPMN starter app uses edge mappings to distinguish between sequence flows and message flows, applying different markers and dash patterns.

export default function getFlowTypes() {
    return [
        {
            property: "type",
            mappings: {
                "sequence": {
                    targetMarker: {
                        type: "PlainArrow",
                        options: { location: 1 }
                    }
                },
                "message": {
                    dashArray: "3",
                    targetMarker: {
                        type: "PlainArrow",
                        options: { hollow: true }
                    },
                    sourceMarker: {
                        type: "Dot",
                        options: { radius: 6, hollow: true }
                    }
                }
            }
        }
    ]
}