Constraints
6 Jun 20195 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
DiagramConstraints
Diagram constraints allow to enable or disable the following behaviors.
- Page Editing
- Line Bridging
- Zoom and Pan
- Undo Redo
- Crisp Edges
- Resizing
For more information about Diagram constraints, refer to Diagram Constraints.
Example
The following example illustrates how to disable page editing.
var DiagramConstraints = ej.datavisualization.Diagram.DiagramConstraints;
//Disables PageEditing
$("#diagram").ejDiagram({
constraints: DiagramConstraints.Default & ~DiagramConstraints.PageEditable
});
NodeConstraints
NodeConstraints allows to enable or disable the following behaviors of node.
- Selection
- Deletion
- Drag
- Resize
- Rotate
- Connect
- Drop shadow
- Drag label
- Define tooltip
- Crisp Edges
- Interaction
For more information about node constraints, refer to Node Constraints
Example
The following code illustrates how to disable rotation.
//Disables rotation
var NodeConstraints = ej.datavisualization.Diagram.NodeConstraints;
var nodes = [{
name: "node",
constraints: NodeConstraints.Default & ~NodeConstraints.Rotate
}];
$("#diagram").ejDiagram({
nodes: nodes,
});
ConnectorConstraints
ConnectorConstraints allow to enable or disable certain behaviors of Connectors. They are as follows.
- Selection
- Deletion
- Drag
- Segment editing
- Define tooltip
- Bridging
- Label dragging
- Crisp Edges
- Interaction
For more information about connector constraints, refer to Connector Constraints
Example
The following code illustrates how to disable selection.
//Disables selection
var ConnectorConstraints = ej.datavisualization.Diagram.ConnectorConstraints;
var connectors = [{
name: "connector",
constraints: ConnectorConstraints.Default & ~ConnectorConstraints.Select
}];
$("#diagram").ejDiagram({
connectors: connectors,
});
PortConstraints
You can enable or disable certain behaviors of Port. They are as follows.
- Connect
- ConnectOnDrag
For more information about port constraints, refer to Port Constraints
Example
The following code illustrates how to disable creating connections with a port.
var PortConstraints = ej.datavisualization.Diagram.PortConstraints;
var nodes = [{
name: "node",
ports: [{
//Sets the port as not getting connected
constraints: PortConstraints.None
}]
}];
$("#diagram").ejDiagram({
nodes: nodes,
});
SelectorConstraints
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.
- Resizer
- Rotator
- User handles
For more information about Selector constraints, refer to Selector Constraints
Example
The following code illustrates how to hide rotator.
var SelectorConstraints = ej.datavisualization.Diagram.SelectorConstraints;
$("#diagram").ejDiagram({
selectedItems: {
//Hides rotator
constraints:SelectorConstraints.All & ~SelectorConstraints.Rotator
}
});
SnapConstraints
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 and vertical gridlines
- Snap to either horizontal or vertical gridlines
- Snap to both horizontal and vertical gridlines
For more information about snap constraints, refer to Snap Constraints
Example
The following code illustrates how to show only horizontal gridlines.
$("#diagram").ejDiagram({
snapSettings: {
//Shows horizontal gridlines
snapConstraints: ej.datavisualization.Diagram.SnapConstraints.ShowHorizontalLines
}
});
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 model.
// Enables/disables line bridging based on the Diagram constraints
var ConnectorConstraints = ej.datavisualization.Diagram.ConnectorConstraints;
var DiagramConstraints = ej.datavisualization.Diagram.DiagramConstraints;
var connectors = [{
name: "connector",
sourcePoint: { x: 100, y: 100 },
targetPoint: { x: 200, y: 200 },
//Sets to inherit bridging from model
constraints: ConnectorConstraints.Default | ConnectorConstraints.InheritBridging
}];
$("#diagram").ejDiagram({
connectors: connectors,
//Enables line bridging for all connectors
constraints: DiagramConstraints.Default | DiagramConstraints.Bridging
});
Bitwise Operations
Bitwise Operations are used to manipulate the flagged enumerations [enum]. In this 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 = ej.datavisualization.Diagram.NodeConstraints.Select | ej.datavisualization.Diagram.NodeConstraints.Rotate;
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.
var NodeConstraints = ej.datavisualization.Diagram.NodeConstraints;
node.constraints = node.constraints & ~(NodeConstraints.Rotate);
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 & (ej.datavisualization.Diagram.NodeConstraints.Rotate)) == (ej.datavisualization.Diagram.NodeConstraints.Rotate));
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.