markgojs/extensionsTS/LinkLabelOnPathDraggingTool.ts

Interactive diagrams, charts, and graphs, such as trees, flowcharts, orgcharts, UML, BPMN, or business diagrams

"use strict";
/*
*  Copyright (C) 1998-2019 by Northwoods Software Corporation. All Rights Reserved.
*/

import * as go from "../release/go";

// A custom Tool for moving a label on a Link that keeps the label on the link's path.

/**
* @constructor
* @extends Tool
* @class
* This tool only works when the Link has a label marked by the "_isLinkLabel" property.
*/
export class LinkLabelOnPathDraggingTool extends go.Tool {
	/** @type {GraphObject} */
	public label: go.GraphObject = null;
	/** @type {number} */
	private _originalIndex: number = null;
	/** @type {number} */
	private _originalFraction: number = null;

	constructor() {
		super();
		this.name = "LinkLabelOnPathDragging";
	}

  /**
	* 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().
	* @this {LinkLabelOnPathDraggingTool}
	* @return {boolean}
	*/
	public canStart(): boolean {
		if (!go.Tool.prototype.canStart.call(this)) return false;
		var diagram = this.diagram;
		if (diagram === null) return false;
		// require left button & that it has moved far enough away from the mouse down point, so it isn't a click
		var e = diagram.lastInput;
		if (!e.left) return false;
		if (!this.isBeyondDragSize()) return false;

		return this.findLabel() !== null;
	}

  /**
  * From the GraphObject at the mouse point, search up the visual tree until we get to
  * an object that has the "_isLinkLabel" property set to true and that is an immediate child of a Link Panel.
  * @this {LinkLabelOnPathDraggingTool}
  * @return {GraphObject} This returns null if no such label is at the mouse down point.
  */
	public findLabel(): go.GraphObject {
		var diagram = this.diagram;
		var e = diagram.lastInput;
		var elt = diagram.findObjectAt(e.documentPoint, null, null);

		if (elt === null || !(elt.part instanceof go.Link)) return null;
		while (elt.panel !== elt.part) {
			elt = elt.panel;
		}
		// If it's not marked as "_isLinkLabel", don't consider it a label:
		if (!(<any>elt)["_isLinkLabel"]) return null;
		return elt;
	};

  /**
  * Start a transaction, call findLabel and remember it as the "label" property,
  * and remember the original values for the label's segment properties.
  * @this {LinkLabelOnPathDraggingTool}
  */
	public doActivate() {
		this.startTransaction("Shifted Label");
		this.label = this.findLabel();
		if (this.label !== null) {
			this._originalIndex = this.label.segmentIndex;
			this._originalFraction = this.label.segmentFraction;
		}
		go.Tool.prototype.doActivate.call(this);
	}

  /**
  * Stop any ongoing transaction.
  * @this {LinkLabelOnPathDraggingTool}
  */
	public doDeactivate() {
		go.Tool.prototype.doDeactivate.call(this);
		this.stopTransaction();
	}

  /**
  * Clear any reference to a label element.
  * @this {LinkLabelOnPathDraggingTool}
  */
	public doStop() {
		this.label = null;
		go.Tool.prototype.doStop.call(this);
	}

  /**
  * Restore the label's original value for GraphObject.segment... properties.
  * @this {LinkLabelOnPathDraggingTool}
  */
	public doCancel() {
		if (this.label !== null) {
			this.label.segmentIndex = this._originalIndex;
			this.label.segmentFraction = this._originalFraction;
		}
		go.Tool.prototype.doCancel.call(this);
	}

  /**
  * During the drag, call updateSegmentOffset in order to set the segment... properties of the label.
  * @this {LinkLabelOnPathDraggingTool}
  */
	public doMouseMove() {
		if (!this.isActive) return;
		this.updateSegmentOffset();
	}

  /**
  * At the end of the drag, update the segment properties of the label and finish the tool,
  * completing a transaction.
  * @this {LinkLabelOnPathDraggingTool}
  */
	public doMouseUp() {
		if (!this.isActive) return;
		this.updateSegmentOffset();
		this.transactionResult = "Shifted Label";
		this.stopTool();
	}

  /**
  * Save the label's GraphObject.segmentIndex and segmentFraction at the closest point to the mouse.
  * @this {LinkLabelOnPathDraggingTool}
  */
	public updateSegmentOffset() {
		var lab = this.label;
		if (lab === null) return;
		var link = lab.part;
		if (!(link instanceof go.Link)) return;

		var last = this.diagram.lastInput.documentPoint;
		var idx = link.findClosestSegment(last);
		idx = Math.min(Math.max(link.firstPickIndex, idx), link.lastPickIndex - 1);
		var p1 = link.getPoint(idx);
		var p2 = link.getPoint(idx + 1);
		var total = Math.sqrt(p1.distanceSquaredPoint(p2));
		var p = last.copy().projectOntoLineSegmentPoint(p1, p2);
		var frac = Math.sqrt(p1.distanceSquaredPoint(p)) / total;
		lab.segmentIndex = idx;
		lab.segmentFraction = frac;
	}

}