gojs/extensionsJSM/LinkLabelDraggingTool.js

/*
*  Copyright (C) 1998-2021 by Northwoods Software Corporation. All Rights Reserved.
*/
/*
* This is an extension and not part of the main GoJS library.
* Note that the API for this class may change with any version, even point releases.
* 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 or extensionsTS folders.
* See the Extensions intro page (https://gojs.net/latest/intro/extensions.html) for more information.
*/
import * as go from '../release/go-module.js';
/**
 * The LinkLabelDraggingTool class lets the user move a label on a {@link Link}.
 *
 * This tool only works when the Link has a label
 * that is positioned at the {@link Link#midPoint} plus some offset.
 * It does not work for labels that have a particular {@link GraphObject#segmentIndex}.
 *
 * If you want to experiment with this extension, try the <a href="../../extensionsJSM/LinkLabelDragging.html">Link Label Dragging</a> sample.
 * @category Tool Extension
 */
export class LinkLabelDraggingTool extends go.Tool {
    /**
     * Constructs a LinkLabelDraggingTool and sets the name for the tool.
     */
    constructor() {
        super();
        /**
         * The label being dragged.
         */
        this.label = null;
        this._offset = new go.Point(); // of the mouse relative to the center of the label object
        this._originalOffset = null;
        this.name = 'LinkLabelDragging';
    }
    /**
     * 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.
     * @return {GraphObject} This returns null if no such label is at the mouse down point.
     */
    findLabel() {
        const diagram = this.diagram;
        const e = diagram.lastInput;
        let elt = diagram.findObjectAt(e.documentPoint, null, null);
        if (elt === null || !(elt.part instanceof go.Link))
            return null;
        while (elt !== null && elt.panel !== elt.part) {
            elt = elt.panel;
        }
        // If it's at an arrowhead segment index, don't consider it a label:
        if (elt !== null && (elt.segmentIndex === 0 || elt.segmentIndex === -1))
            return null;
        return elt;
    }
    /**
     * 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 {@link #findLabel}.
     */
    canStart() {
        if (!super.canStart())
            return false;
        const diagram = this.diagram;
        // require left button & that it has moved far enough away from the mouse down point, so it isn't a click
        const e = diagram.lastInput;
        if (!e.left)
            return false;
        if (!this.isBeyondDragSize())
            return false;
        return this.findLabel() !== null;
    }
    /**
     * Start a transaction, call {@link #findLabel} and remember it as the "label" property,
     * and remember the original value for the label's {@link GraphObject#segmentOffset} property.
     */
    doActivate() {
        this.startTransaction('Shifted Label');
        this.label = this.findLabel();
        if (this.label !== null) {
            // compute the offset of the mouse-down point relative to the center of the label
            this._offset = this.diagram.firstInput.documentPoint.copy().subtract(this.label.getDocumentPoint(go.Spot.Center));
            this._originalOffset = this.label.segmentOffset.copy();
        }
        super.doActivate();
    }
    /**
     * Stop any ongoing transaction.
     */
    doDeactivate() {
        super.doDeactivate();
        this.stopTransaction();
    }
    /**
     * Clear any reference to a label element.
     */
    doStop() {
        this.label = null;
        super.doStop();
    }
    /**
     * Restore the label's original value for {@link GraphObject#segmentOffset}.
     */
    doCancel() {
        if (this.label !== null && this._originalOffset !== null) {
            this.label.segmentOffset = this._originalOffset;
        }
        super.doCancel();
    }
    /**
     * During the drag, call {@link #updateSegmentOffset} in order to set
     * the {@link GraphObject#segmentOffset} of the label.
     */
    doMouseMove() {
        if (!this.isActive)
            return;
        this.updateSegmentOffset();
    }
    /**
     * At the end of the drag, update the segment offset of the label and finish the tool,
     * completing a transaction.
     */
    doMouseUp() {
        if (!this.isActive)
            return;
        this.updateSegmentOffset();
        this.transactionResult = 'Shifted Label';
        this.stopTool();
    }
    /**
     * Save the label's {@link GraphObject#segmentOffset} as a rotated offset from the midpoint of the
     * Link that the label is in.
     */
    updateSegmentOffset() {
        const lab = this.label;
        if (lab === null)
            return;
        const link = lab.part;
        if (!(link instanceof go.Link))
            return;
        const last = this.diagram.lastInput.documentPoint;
        const idx = lab.segmentIndex;
        const numpts = link.pointsCount;
        // if the label is a "mid" label, assume it is positioned differently from a label at a particular segment
        if (idx < -numpts || idx >= numpts) {
            const mid = link.midPoint;
            // need to rotate this point to account for the angle of the link segment at the mid-point
            const p = new go.Point(last.x - this._offset.x - mid.x, last.y - this._offset.y - mid.y);
            lab.segmentOffset = p.rotate(-link.midAngle);
        }
        else { // handle the label point being on a partiular segment with a given fraction
            const frac = lab.segmentFraction;
            let a;
            let b;
            if (idx >= 0) { // indexing forwards
                a = link.getPoint(idx);
                b = (idx < numpts - 1) ? link.getPoint(idx + 1) : a;
            }
            else { // or backwards if segmentIndex is negative
                const i = numpts + idx;
                a = link.getPoint(i);
                b = (i > 0) ? link.getPoint(i - 1) : a;
            }
            const labx = a.x + (b.x - a.x) * frac;
            const laby = a.y + (b.y - a.y) * frac;
            const p = new go.Point(last.x - this._offset.x - labx, last.y - this._offset.y - laby);
            const segangle = (idx >= 0) ? a.directionPoint(b) : b.directionPoint(a);
            lab.segmentOffset = p.rotate(-segangle);
        }
    }
}