I

IEditLabelHelper

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Helper interface to handle interactive label editing.
Inheritance Hierarchy

Remarks

Implementations of this interface are by default retrieved from the ILookup of ILabelOwners and ILabels. If needed, different implementations can be decorated so that it is possible to tweak the behavior on a case by case basis. Hiding the implementation for both an ILabel and its owner can prevent adding or editing labels interactively.

Implementations have to handle ADDing or removing labels or changing a label's text upon finish. Unless developers want to implement all of these actions themselves, it is recommended to either wrap the default implementation or extend EditLabelHelper and call its base methods.

Developers who simply want to change the editing behavior via the LabelEditingEventArgs might also consider handling the query-label-adding and query-label-editing events.

Examples

A wrapper to customize a single aspect of edge editing
class WrappingEditLabelHelper extends BaseClass(IEditLabelHelper) {
  private wrapped!: IEditLabelHelper

  public WrappingEditLabelHelper(wrapped: IEditLabelHelper) {
    this.wrapped = wrapped
  }

  public initialize(
    context: IInputModeContext,
    evt: LabelEditingEventArgs,
    action: LabelEditingAction,
  ): void {
    // let the wrapped implementation do the work
    this.wrapped.initialize(context, evt, action)
    // for new edge labels: use a custom parameter
    if (action == LabelEditingAction.ADD && evt.owner instanceof IEdge) {
      evt.layoutParameter =
        new EdgeSegmentLabelModel().createParameterFromCenter()
    }
  }

  // Finish completely delegates to the wrapped implementation
  public finish(
    context: IInputModeContext,
    evt: LabelEditingEventArgs,
    action: LabelEditingAction,
  ): ILabel | null {
    return this.wrapped.finish(context, evt, action)
  }

  // Cancel completely delegates to the wrapped implementation
  public cancel(
    context: IInputModeContext,
    evt: LabelEditingEventArgs,
  ): void {
    this.wrapped.cancel(context, evt)
  }
}
Wrapping the edge's IEditLabelHelper
graph.decorator.edges.editLabelHelper.addWrapperFactory(
  (label, helper) => new WrappingEditLabelHelper(helper),
)

See Also

Developer's Guide

API

EditLabelHelper, startLabelEditing, startLabelAddition, query-label-adding, query-label-editing

Members

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Methods

cancel

(context: IInputModeContext, evt: LabelEditingEventArgs)
abstract
Invoked if the label editing action has been canceled.
Implementations which maintain a state have to clean up here.
abstract

Parameters

context: IInputModeContext
The current input mode context.
evt: LabelEditingEventArgs
Additional information about the label or label owner and whether the editing operation has been canceled programmatically.

See Also

Developer's Guide

finish

(
context: IInputModeContext
evt: LabelEditingEventArgs
action: LabelEditingAction
): ILabel
abstract
Invoked after the label editing gesture has successfully finished.

Depending on the action, implementations have to either ADD a new label, change the text of the given label, or REMOVE the given label.

For operations that fail or are not supported by the implementation, this method has to return null.

Implementations which maintain a state have to clean up here.

abstract

Parameters

context: IInputModeContext
The input mode context from the input mode which invoked that method.
evt: LabelEditingEventArgs
The LabelEditingEventArgs which provide the information for the label to be added or edited. In particular, evt provides the owner for newly added labels or the label to edit or remove, and the text to set when adding or editing labels.
action: LabelEditingAction
Whether to ADD a new label or EDIT or REMOVE an existing label.

Return Value

ILabel
The added, edited, or removed label if the action has been completed successfully and null otherwise.

See Also

Developer's Guide

initialize

(
context: IInputModeContext
evt: LabelEditingEventArgs
action: LabelEditingAction
)
abstract
Invoked at the beginning of a label adding or label editing gesture.

The LabelEditingEventArgs can be configured to customize the label editing behavior. It is also possible to set a custom label or owner. Finally, label editing can be prevented by setting cancel to true.

Implementations which need to maintain a state can configure the state here and clean it up in both finish and cancel. It is important, that these implementations set LabelEditingEventArgs's handled to true to make sure that no other IEditLabelHelper implementation takes over.

abstract

Parameters

context: IInputModeContext
The input mode context from the input mode which invoked that method.
evt: LabelEditingEventArgs
A configuration object which supports customizing the label editing.
action: LabelEditingAction
Whether to ADD a new label, EDIT an existing label, or create a new label during DROP or PASTE.

See Also

Developer's Guide

Static Methods

create

(): IEditLabelHelper
static
static

Parameters

Return Value

IEditLabelHelper