This is an extension and not part of the main GoJS library. Note that the API for this class may change at any time. If you intend to use an extension in production, you should copy the code to your own source directory. Extensions can be found in the GoJS kit under the extensions (for loading via script tags),extensionsTS (UMD modules), or extensionsJSM (ES6 modules) folders. See the Extensions intro page for more information.
Constructs a LinkLabelDraggingTool and sets the name for the tool.
The label being dragged.
This tool can only start if the mouse has moved enough so that it is not a click, and if the mouse down point is on a GraphObject "label" in a Link Panel, as determined by findLabel.
Start a transaction, call findLabel and remember it as the "label" property, and remember the original value for the label's GraphObject.segmentOffset property.
Restore the label's original value for GraphObject.segmentOffset.
Stop any ongoing transaction.
During the drag, call updateSegmentOffset in order to set the GraphObject.segmentOffset of the label.
At the end of the drag, update the segment offset of the label and finish the tool, completing a transaction.
Clear any reference to a label element.
From the GraphObject at the mouse point, search up the visual tree until we get to an object that is a label of a Link.
This returns null if no such label is at the mouse down point.
Save the label's GraphObject.segmentOffset as a rotated offset from the midpoint of the Link that the label is in.
The LinkLabelDraggingTool class lets the user move a label on a Link.
This tool only works when the Link has a label that is positioned at the Link.midPoint plus some offset. It does not work for labels that have a particular GraphObject.segmentIndex.
If you want to experiment with this extension, try the Link Label Dragging sample.