Constraints in UWP Diagram (SfDiagram)

10 May 20218 minutes to read

Constraints are used to enable/disable certain behaviors of the diagram, Node and Connector. Constraints are provided as flagged enumerations, so that multiple behaviors can be enabled/disabled with bitwise operators (&, |, ~, «, etc.).
To know more about bitwise operators, refer to Bitwise Operations.

Graph Constraints

Graph constraints allow to enable or disable the following behaviors.

Page Editing
Line Bridging
Zoom and Pan
Undo Redo

Example

The following example illustrates how to disable page editing.

//Disables PageEditing
diagram.Constraints = GraphConstraints.Default & ~GraphConstraints.PageEditing;

Node Constraints

NodeConstraints allow to enable or disable the following behaviors of Node.

Selection
Deletion
Drag
Resize
Rotate
Connect
Annotation Dragging

Example

The following code illustrates how to disable rotation.

ObservableCollection<Node> nodes = new ObservableCollection<Node>();

Node node = new Node()
{
  //Disables Rotation	
  Constraints = NodeConstraints.Default & ~NodeConstraints.Rotatable,
  UnitWidth = 50,
  UnitHeight = 50,
  OffsetX = 100,
  OffsetY = 100,
  Shape = new RectangleGeometry() { Rect = new Rect(0, 0, 10, 10) },
  ShapeStyle = this.diagram.Resources["shapestyle"] as Style
};

nodes.Add(node);
diagram.Nodes = nodes;

Connector Constraints

ConnectorConstraints allow to enable or disable certain behaviors of Connectors. They are as follows.

Selection
Deletion
Drag
Segment editing
Bridging
Annotation dragging

Example

The following code illustrates how to disable selection.

ObservableCollection<Connector> connectors = new ObservableCollection<Connector>();

Connector connector1 = new Connector()
{
	//Disables Selection
	Constraints = ConnectorConstraints.Default & ~ConnectorConstraints.Selectable
};

connectors.Add(connector1);
diagram.Connectors = connectors;

Port Constraints

You can enable or disable certain behaviors of port. They are as follows.

Connect

Example

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

Node node = new Node()
{
	Ports = new ObservableCollection<INodePort>()
	{
		new NodePort()
		{
			//Sets the Port as not connectable
			Constraints = PortConstraints.None
		}
	},
	UnitWidth = 50,
	UnitHeight = 50,
	OffsetX = 100,
	OffsetY = 100,
};

nodes.Add(node);
diagram.Nodes = nodes;

Annotation Constraints

AnnotationConstraints allow to enable or disable the following behaviors of Annotation.

Selection
Drag
Resize
Rotate

Example
the following code illustrates how to enable annotation dragging.

//Create NodeViewModel (Shape and ShapeStyle Applied from "Data-Binding"
            NodeViewModel node = new NodeViewModel()
            {
                OffsetX = 200,
                OffsetY = 200,
                UnitWidth = 100,
                UnitHeight = 50,
                //Initialize and Add annotation to NodeViewModel
                Annotations = new ObservableCollection<IAnnotation>()
                    {
                        //Create a AnnotationEditorViewModel
                        new AnnotationEditorViewModel()
                        {
                            Content = "Annotation",
                            //Assign Constraint to Select and Drag.
                            Constraints =AnnotationConstraints.Selectable |AnnotationConstraints.Draggable,                            
                        }          
                    }
            };
            //Add NodeViewModel to Nodes Collection
            (Diagram.Nodes as NodeCollection).Add(node);

Selector Constraints

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

Resizer
Rotator
Quick Commands

Example

The following code illustrates how to hide rotator.

//Hides Rotator
(diagram.SelectedItems as SelectorViewModel).SelectorConstraints = (diagram.SelectedItems as  SelectorViewModel).SelectorConstraints & ~SelectorConstraints.Rotator;

Snap Constraints

Snap Constraints control the visibility of gridlines and enable/disable snapping. Snap constraints allow to set the following behaviors.

Show only Horizontal or Vertical Gridlines
Show both Horizontal or Vertical Gridlines
Show to either Horizontal or Vertical Gridlines
Show to both Horizontal or vertical gridlines

Example

The following code illustrates how to show only Horizontal Gridlines

//Shows Horizontal Gridlines
diagram.SnapSettings.SnapConstraints = SnapConstraints.SnapToHorizontalLines;

Inherit behaviors

Some of the behaviors can be defined through both the specific object (Node/Connector) and Diagram. When the behaviors are contradictorily defined through both, the actual behavior is set through inherit options.

The following code example illustrates how to inherit the line bridging behavior from the Diagram.

//Enables Bridging
diagram.Constraints = GraphConstraints.Default | GraphConstraints.Bridging;

ObservableCollection<Connector> connectors = new ObservableCollection<Connector>();

Connector connector1 = new Connector()
{
	SourcePoint=new Point(100,100),
	TargetPoint=new Point(200,200),
	//Sets to InheritBridge 
	Constraints = ConnectorConstraints.Default | ConnectorConstraints.InheritBridging
};

connectors.Add(connector1);
diagram.Connectors = connectors;

Bitwise Operations

Bitwise Operations are used to manipulate the flagged enumerations [enum]. In the section, Bitwise Operations are illustrated by using Node Constraints. The same is applicable while working with Node Constraints, Connector Constraints, or Port Constraints.

Add Operation

You can add or enable multiple values at a time by using Bitwise ‘

’ (OR) operator.

node.Constraints = NodeConstraints.Selectable | NodeConstraints.Rotatable;

In the above example, you can do both the selection and rotation.

Remove Operation

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

node.Constraints = node.Constraints & ~(NodeConstraints.Rotatable);

In the above example, Rotation is disabled but other constraints are enabled.

Check Operation

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

if ((node.Constraints & (NodeConstraints.Rotatable)) == (NodeConstraints.Rotatable))

In the above example, you can check whether the rotate constraints are enabled in a Node. When Node constraints have rotate constraints, the expression returns a rotate constraint.