Constraints in Blazor Diagram Component

7 Jul 202224 minutes to read

Constraints are used to enable or disable certain behaviors of the diagram, nodes, and connectors. Constraints are provided as flagged enumerations, so that multiple behaviors can be enabled or disabled using the Bitwise operators (&, |, ~, <<, etc.).

To know more about Bitwise operators, refer to the Bitwise Operations.

Diagram constraints

DiagramConstraints allow you to enable or disable the following behaviors.

  • PageEditable
  • Bridging
  • Zoom
  • UndoRedo
  • UserInteraction
Constraints Description
None Disable all diagram functionalities.
Bridging Enables or disables Bridging support for connector in diagram.
Undo/redo Enables or disables the Undo/Redo support for the diagram.
UserInteraction Enables or disables user interaction support for the diagram.
ApiUpdate Enables or disables update API support for the diagram.
PageEditable Enables or disables Page Editable support for the diagram.
Zoom Enables or disables Zoom support for the diagram.
PanX Enables or disables Panning X coordinate support for the diagram.
PanY Enables or disables Panning Y coordinate support for the diagram.
Pan Enables or disables panning both X and Y coordinates support for the diagram.
ZoomTextEdit Enables or disables zooming the text box while editing the text.
Default Enables or disables all constraints in diagram.

The following example shows how to disable PageEditable constraint from default diagram constraints.

@using Syncfusion.Blazor.Diagram

@* Initialize the diagram with constraints *@
<SfDiagramComponent Height="600px" Nodes="@nodes" 
Constraints="@DiagramConstraints" />

@code
{
    //Sets the Diagram constraints.
    DiagramConstraints DiagramConstraints = DiagramConstraints.Default & ~DiagramConstraints.PageEditable;
    //Initialize the Nodes Collection.
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        Node node = new Node()
        {
            ID = "node1",
            Height = 100,
            Width = 100,
            OffsetX = 100,
            OffsetY = 100,
        };
        nodes.Add(node);
    }
}

The following example shows how to add Bridging constraint to the default constraints of diagram.

DiagramConstraints DiagramConstraints = DiagramConstraints.Default | DiagramConstraints.Bridging;

The diagram constraints are provided as flagged enumerations, so that multiple behaviors can be added or removed from the default constraints using the Bitwise Operations in the diagram.

//Removing multiple constraints from default.
DiagramConstraints DiagramConstraints = DiagramConstraints.Default & ~(DiagramConstraints.PageEditable|DiagramConstraints.Zoom);

For more information about diagram constraints, refer to the Diagram constraints.

By default, the following constraints are enabled in the diagram,

  • ApiUpdate
  • PanX
  • PanY
  • Pan
  • ZoomTextEdit
  • Default
  • None

Node constraints

The Constraints property of the Node allows you to enable or disable the following behaviors.

  • Select
  • Drag
  • Resize
  • Rotate
  • Delete
  • InConnect
  • OutConnect
Constraints Description
None Disable all node Constraints
Select Enables or disables the node to be selected.
Drag Enables or disables the node to be dragged.
Rotate Enables or disables the node to be rotated.
Shadow Enables or disables the node to display shadow.
PointerEvents Enables or disables the node to provide pointer option.
Delete Enables or disables node to be deleted.
InConnect Enables or disables node to provide in connect option.
OutConnect Enables or disables node to provide out connect option.
AllowDrop Enables node to provide allow to drop option.
ResizeNorthEast Enable or disable to resize NorthEast side of the node.
ResizeEast Enable or disable to resize East side of the node.
ResizeSouthEast Enable or disable to resize SouthEast side of the node.
ResizeSouth Enable or disable to resize South side of the node.
ResizeSouthWest Enable or disable to resize SouthWest side of the node.
ResizeWest Enable or disable to resize West side of the node.
ResizeNorthWest Enable or disable to resize NorthWest side of the node.
ResizeNorth Enable or disable to resize North side of the node.
AspectRatio Enables the Aspect ratio of the node.
ReadOnly Enables the ReadOnly support for annotation in the node.
HideThumbs Enable to hide all resize thumbs for the node.
Resize Enables or Disables the expansion or compression of a node.
Inherit Enables the node to inherit the interaction option from the parent object.
Default Enables all default constraints for the node.

The following example shows how to disable rotate constraint from the default node constraints.

@using Syncfusion.Blazor.Diagram

@* Initialize the diagram with NodeCollection *@
<SfDiagramComponent Height="600px" Nodes="@nodes" />

@code
{
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        Node node = new Node()
        {
            ID = "node1",
            Height = 100,
            Width = 100,
            OffsetX = 100,
            OffsetY = 100,
            Style = new ShapeStyle() { Fill = "#6495ED", StrokeColor = "White" },
            //Sets the NodeConstraints constraints.
            Constraints = NodeConstraints.Default & ~NodeConstraints.Rotate
        };
        nodes.Add(node);
    }
}

Node Constraints in Blazor Diagram

The following example shows how to add Shadow constraint to the default constraints of node.

NodeConstraints NodeConstraints = NodeConstraints.Default | NodeConstraints.Shadow;

The node constraints are provided as flagged enumerations, so that multiple behaviors can be added or removed from the default constraints using the Bitwise Operations.

 //Removing multiple constraints from default.
NodeConstraints NodeConstraints = NodeConstraints.Default & ~ (NodeConstraints.Select | NodeConstraints.Drag);

For more information about node constraints, refer to the NodeConstraints.

Note : By default, the following constraints are enabled for the node,

  • Shadow
  • PointerEvents
  • AllowDrop
  • ResizeNorthEast
  • ResizeEast
  • ResizeSouthEast
  • ResizeSouth
  • ResizeSouthWest
  • ResizeWest
  • ResizeNorthWest
  • ResizeNorth
  • AspectRatio
  • ReadOnly
  • HideThumbs
  • Inherit
  • Default

Connector constraints

The Constraints property of the Connector allows you to enable or disable the following behaviors of connectors.

  • Select
  • Drag
  • DragSourceEnd
  • DragTargetEnd
  • Delete
  • InheritBridging
  • PointerEvents
Constraints Description
None Disable all connector Constraints.
Select Enables or disables node to be selected.
Delete Enables or disables node to be deleted.
Drag Enables or disables node to be dragged.
DragSourceEnd Enables connectors source end to be selected.
DragTargetEnd Enables connectors target end to be selected.
DragSegmentThumb Enables control point and end point of every segment in a connector for editing.
Interaction Enables or disables Interaction for the connector.
AllowDrop Enables allow drop support to the connector.
Bridging Enables bridging to the connector.
InheritBridging Enables to inherit bridging option from the parent object.
PointerEvents Enables to set the pointer events.
ConnectToNearByNode Enables to connect to the nearest node.
ConnectToNearByPort Enables to connect to the nearest port.
ConnectToNearByElement Enables to connect to the nearest elements.
ReadOnly Enables or disables readonly for the connector.
Default Enables all constraints for the connector.

The following code shows how to disable select constraint from the default constraints of connector.

@using Syncfusion.Blazor.Diagram

@* Initialize the diagram with connectors *@
<SfDiagramComponent Height="600px" Connectors="@connectors" />

@code
{
    DiagramObjectCollection<Connector> connectors;

    protected override void OnInitialized()
    {
        connectors = new DiagramObjectCollection<Connector>();
        Connector connector = new Connector()
        {
            ID = "connector1",
            Type = ConnectorSegmentType.Straight,
            SourcePoint = new DiagramPoint() { X = 100, Y = 100 },
            TargetPoint = new DiagramPoint() { X = 200, Y = 200 },
            //Sets the ConnectorConstraints.
            Constraints = ConnectorConstraints.Default & ~ConnectorConstraints.Select
        };
        connectors.Add(connector);
    }
}

The following example shows how to add Bridging constraint to the default constraints of connector.

ConnectorConstraints ConnectorConstraints = ConnectorConstraints.Default | ConnectorConstraints.Bridging;

The connector constraints are provided as flagged enumerations, so that multiple behaviors can be added or removed from the default constraints using the Bitwise Operations.

//Removing multiple constraints from default.
ConnectorConstraints ConnectorConstraints = ConnectorConstraints.Default & ~ (ConnectorConstraints.Select | ConnectorConstraints.Drag);

For more information about connector constraints, refer to the ConnectorConstraints.

By default, the following constraints are enabled for the connector,

  • DragSegmentThumb
  • Interaction
  • AllowDrop
  • Bridging
  • InheritBridging
  • ConnectToNearByNode
  • ConnectToNearByPort
  • ConnectToNearByElement
  • ReadOnly
  • Default

Port constraints

The Constraints property of the Port allows you to enable or disable the following behaviors of port.

  • InConnect
  • OutConnect
Constraints Description
None Disable all port Constraints.
Draw Enables to create the connection when mouse hover on the port.
InConnect Enables or disables to connect only the target end of connector.
OutConnect Enables or disables to connect only the source end of connector.
Default Enables all constraints for the port.

The following code shows how to disable creating connections with a port.

@using Syncfusion.Blazor.Diagram

@* Initialize the diagram with NodeCollection *@
<SfDiagramComponent Height="600px" Nodes="@nodes" />

@code
{
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        // Initialize the NodeCollection.
        nodes = new DiagramObjectCollection<Node>();
        Node node = new Node()
        {
            ID = "node1",
            Height = 100,
            Width = 100,
            OffsetX = 100,
            OffsetY = 100,
        };
        node.Ports = new DiagramObjectCollection<PointPort>()
        {
            new PointPort()
            {
                ID="port1",
                Offset=new DiagramPoint(){X=0,Y=0.5},
                Shape=PortShapes.Circle,
                Visibility=PortVisibility.Visible,
                // Sets the PortConstraints.
                Constraints=PortConstraints.None
            }
        };
        nodes.Add(node);
    }
}

The following code example shows how to modify the port constraints to accept target connection alone.

//Enable to create target connection alone.
port.Constraints = PortConstraints.InConnect;

The port constraints are provided as flagged enumerations, so that multiple behaviors can be added or removed from the default constraints using the Bitwise Operations.

//Enable to create target connection alone.
port.Constraints = PortConstraints.Default | PortConstraints.Draw;

For more information about port constraints, refer to the PortConstraints.

By default, the following constraints are enabled for the port,

  • Draw
  • Default

Annotation constraints

The Constraints property of the Annotations allows you to enable or disable read-only mode for the annotations by using the annotation constraints.

Constraints Description
ReadOnly Enables or disables the ReadOnly Constraints,
InheritReadOnly Enables or disables to inherit the ReadOnly option from the parent object.
None Disables all constraints for the annotation.

The following code shows how to enable read-only mode for the annotations.

@using Syncfusion.Blazor.Diagram

@* Initialize the diagram with NodeCollection *@
<SfDiagramComponent Height="600px" Nodes="@nodes" />

@code
{
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        //Initialize the NodeCollection.
        nodes = new DiagramObjectCollection<Node>();
        Node node = new Node()
        {
            ID = "node1",
            Height = 100,
            Width = 100,
            OffsetX = 100,
            OffsetY = 100,
        };
        node.Annotations = new DiagramObjectCollection<ShapeAnnotation>()
        {
            new ShapeAnnotation()
            {
                ID="annotation1",
                Content="Annotation Text Wrapping",
                // Sets the Constraints for Annotation.
                Constraints=AnnotationConstraints.ReadOnly,
                Style= new TextStyle()
                {
                    Color="#000000",
                    Fill="Transparent",
                    FontFamily="TimesNewRoman",
                    FontSize=12,
                    Bold=true,
                    Italic=true
                },
            }
        };
        nodes.Add(node);
    }
}

For more details about annotation constraints, refer to the AnnotationConstraints.

Selector constraints

Selector visually represents the selected elements with certain editable thumbs. The visibility of the thumbs can be controlled with selector constraints. The part of selector is categorized as follows:

  • ResizeAll
  • UserHandle
  • Rotate
Constraints Description
None Hides all the selector elements.
ConnectorSourceThumb Shows or hides the source thumb of the connector.
ConnectorTargetThumb Shows or hides the target thumb of the connector.
ResizeSouthEast Shows or hides the bottom right resize handle of the selector.
ResizeSouthWest Shows or hides the bottom left resize handle of the selector.
ResizeNorthEast Shows or hides the top right resize handle of the selector.
ResizeNorthWest Shows or hides the top left resize handle of the selector.
ResizeEast Shows or hides the middle right resize handle of the selector.
ResizeWest Shows or hides the middle left resize handle of the selector.
ResizeSouth Shows or hides the bottom center resize handle of the selector.
ResizeNorth Shows or hides the top center resize handle of the selector.
Rotate Shows or hides the rotate handle of the selector.
UserHandle Shows or hides the user handles of the selector.
ResizeAll Shows or hides all resize handles of the selector.
All Shows all handles of the selector.

The following code shows how to hide rotator.

@using Syncfusion.Blazor.Diagram

<SfDiagramComponent Height="600px" Nodes="@nodes" SelectionSettings="@selectionSettings"/>

@code
{
    DiagramObjectCollection<Node> nodes;
    public DiagramSelectionSettings selectionSettings = new DiagramSelectionSettings() 
    { 
        Constraints = SelectorConstraints.All & ~SelectorConstraints.Rotate 
    };

    protected override void OnInitialized()
    {
        //Initialize the NodeCollection.
        nodes = new DiagramObjectCollection<Node>();
        Node node = new Node()
        {
            ID = "node1",
            Height = 100,
            Width = 100,
            OffsetX = 100,
            OffsetY = 100,
        };
        nodes.Add(node);
    }
}

Selector Constraints in Blazor Diagram

Element should be in selected state, then only Rotator, UserHandle and Resizer thumbs will be visible.

The following another code example shows how to disable the userhandle functionality for the selected item.

//Enable userhandle constraint for the selected item.
selectedItems.Constraints = SelectorConstraints.All &~ SelectorConstraints.UserHandle;

For more information about selector constraints, refer to the SelectorConstraints.

By default, the following constraints are enabled for the selected items,

  • ConnectorSourceThumb
  • ConnectorTargetThumb
  • ResizeSouthEast
  • ResizeSouthWest
  • ResizeEast
  • ResizeWest
  • ResizeSouth
  • ResizeNorth
  • All

Snap constraints

The Constraints property of the SnapConstraints control the visibility of gridlines and enable or disable snapping. Snap constraints allow to set the following behaviors.

  • Show only horizontal or vertical gridlines.
  • Show both horizontal and vertical gridlines.
  • Snap to either horizontal or vertical gridlines.
  • Snap to both horizontal and vertical gridlines.

The following list of snapping constraints are used to enable or disable certain features of snapping.

Constraints Description
None Disable snapping the nodes/connectors in diagram.
ShowHorizontalLines Displays only the horizontal gridlines in diagram.
ShowVerticalLines Displays only the Vertical gridlines in diagram.
ShowLines Display both Horizontal and Vertical gridlines.
SnapToHorizontalLines Enables the object to snap only with horizontal gridlines.
SnapToVerticalLines Enables the object to snap only with Vertical gridlines.
SnapToLines Enables the object to snap with both horizontal and Vertical gridlines.
SnapToObject Enables the object to snap with the other objects in the diagram.
All Shows gridlines and enables snapping.

The following code shows how to show only horizontal gridlines.

@using Syncfusion.Blazor.Diagram

<SfDiagramComponent Height="600px" Nodes="@nodes">
    @* Initialize the snapsettings with constraints *@
    <SnapSettings Constraints="SnapConstraints.ShowHorizontalLines" />
</SfDiagramComponent>

@code
{
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        //Initialize the NodeCollection.
        nodes = new DiagramObjectCollection<Node>();
        Node node = new Node()
        {
            ID = "node1",
            Height = 100,
            Width = 100,
            OffsetX = 100,
            OffsetY = 100,
        };
        nodes.Add(node);
    }
}

The snap constraints are provided as flagged enumerations, so that multiple behaviors can be added or removed from the default constraints using the Bitwise Operations.

snapconstraints = SnapConstraints.ShowHorizontalLines | SnapConstraints.ShowVerticalLines | SnapConstraints.ShowLines;

For more information about snap constraints, refer to the SnapConstraints.

By default, the following constraints are enabled for the snap functionality in the diagram,

  • ShowLines
  • ShowVerticalLines
  • ShowHorizontalLines
  • SnapToHorizontalLines
  • SnapToObject
  • All

Boundary constraints

Boundary constraints defines a boundary for the diagram inside that the interaction should be done. Boundary constraints allow to set the following behaviors.

  • Infinity
  • Diagram
  • Page

The following list of constraints are used to enable or disable certain features of boundary interactions of the diagram.

Constraints Description
Infinity Allow the interactions to take place at the infinite height and width.
Diagram Allow the interactions to take place around the diagram height and width.
Page Allow the interactions to take place around the page height and width.

The following code shows how to limit the interaction done inside a diagram within a page.

@using Syncfusion.Blazor.Diagram

<SfDiagramComponent Height="600px" Nodes="@nodes">
    @* Initialize the pagesettings with boundary constraints *@
    <PageSettings Width="600" Height="500" BoundaryConstraints="BoundaryConstraints.Page"/>
</SfDiagramComponent>

@code
{
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        //Initialize the NodeCollection.
        nodes = new DiagramObjectCollection<Node>();
        Node node = new Node()
        {
            ID = "node1",
            Height = 100,
            Width = 100,
            OffsetX = 100,
            OffsetY = 100,
        };
        nodes.Add(node);
    }
}

For more information about selector constraints, refer to the BoundaryConstraints.

By default, the following boundary constraints are enabled for the snap functionality in the diagram,

  • Diagram

Inherit behaviors

Some of the behaviors can be defined through both the specific object (node or connector) and diagram. When the behaviors are contradictorily defined through both, the actual behavior is set through inherit options.

The following code example shows how to inherit the line bridging behavior from the diagram.

@using Syncfusion.Blazor.Diagram

@* Initialize the diagram with constraints *@
<SfDiagramComponent Height="600px"
                    Connectors="@connectors"
                    Constraints="@diagramConstraints">
</SfDiagramComponent>

@code
{
    //Sets the diagram constraints.
    DiagramConstraints diagramConstraints = DiagramConstraints.Default | DiagramConstraints.Bridging;
    DiagramObjectCollection<Connector> connectors;

    protected override void OnInitialized()
    {
        connectors = new DiagramObjectCollection<Connector>();
        Connector connector = new Connector()
        {
            ID = "connector1",
            SourcePoint = new DiagramPoint() { X = 100, Y = 100 },
            TargetPoint = new DiagramPoint() { X = 200, Y = 200 },
            //Sets the ConnectorConstraints.
            Constraints = ConnectorConstraints.Default | ConnectorConstraints.InheritBridging
        };
        Connector connector1 = new Connector()
        {
            ID = "connector2",
            SourcePoint = new DiagramPoint() { X = 200, Y = 100 },
            TargetPoint = new DiagramPoint() { X = 100, Y = 200 },
        };
        connectors.Add(connector);
        connectors.Add(connector1);
    }
}

Bitwise operations

Bitwise operations are used to manipulate the flagged enumerations enum. In this section, Bitwise operations are shown by using the node constraints. The same is applicable when working with node constraints, connector constraints, or port constraints.

Add operation

You can add or enable multiple values at a time by using the Bitwise | (OR) operator.

The following code shows how to add bridging constraints into the default diagram constraints to enable bridging functionality in the diagram.

@using Syncfusion.Blazor.Diagram

<SfDiagramComponent Height="600px" Constraints="@diagramConstraint"/>

@code
{
    //To add line routing constraint with default contraints.
    DiagramConstraints diagramConstraint = DiagramConstraints.Default | DiagramConstraints.Bridging;
}

Remove operation

You can remove or disable values by using the Bitwise ‘&~’ (XOR) operator.

The following code shows to remove zoom and pan constraints from the default constraints to disable zoom and panning functionality in the diagram.

@using Syncfusion.Blazor.Diagram

<SfDiagramComponent Height="600px" Constraints="@diagramConstraint"/>

@code
{
    //To remove zoom and panning constraints from the default constraints.
    //It has disabled zoom and panning functionality for the diagram.
    DiagramConstraints diagramConstraint = DiagramConstraints.Default &~ (DiagramConstraints.Zoom | DiagramConstraints.Pan);
}

Check operation

You can check any value by using the Bitwise ‘&’ (AND) operator.

if ((node.constraints & (NodeConstraints.Rotate)) == (NodeConstraints.Rotate));

In the previous example, check whether the rotate constraints are enabled in a node. When node constraints have rotated constraints, the expression returns a rotate constraint.