gojs/extensionsJSM/LinkLabelOnPathDraggingTool.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 LinkLabelOnPathDraggingTool class lets the user move a label on a {@link Link} while keeping the label on the link's path.
 * This tool only works when the Link has a label marked by the "_isLinkLabel" property.
 *
 * If you want to experiment with this extension, try the <a href="../../extensionsJSM/LinkLabelOnPathDragging.html">Link Label On Path Dragging</a> sample.
 * @category Tool Extension
 */
export class LinkLabelOnPathDraggingTool extends go.Tool {
    /**
     * Constructs a LinkLabelOnPathDraggingTool and sets the name for the tool.
     */
    constructor() {
        super();
        /**
         * The label being dragged.
         */
        this.label = null;
        this._originalFraction = 0.0;
        this.name = 'LinkLabelOnPathDragging';
    }
    /**
     * 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.
     * @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 not marked as "_isLinkLabel", don't consider it a label:
        if (!elt['_isLinkLabel'])
            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 findLabel and remember it as the "label" property,
     * and remember the original values for the label's segment properties.
     */
    doActivate() {
        this.startTransaction('Shifted Label');
        this.label = this.findLabel();
        if (this.label !== null) {
            this._originalFraction = this.label.segmentFraction;
        }
        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 GraphObject.segment... properties.
     */
    doCancel() {
        if (this.label !== null) {
            this.label.segmentFraction = this._originalFraction;
        }
        super.doCancel();
    }
    /**
     * During the drag, call {@link #updateSegmentOffset} in order to set the segment... properties of the label.
     */
    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.
     */
    doMouseUp() {
        if (!this.isActive)
            return;
        this.updateSegmentOffset();
        this.transactionResult = 'Shifted Label';
        this.stopTool();
    }
    /**
     * Save the label's {@link GraphObject#segmentFraction}
     * at the closest point to the mouse.
     */
    updateSegmentOffset() {
        const lab = this.label;
        if (lab === null)
            return;
        const link = lab.part;
        if (!(link instanceof go.Link) || link.path === null)
            return;
        const last = this.diagram.lastInput.documentPoint;
        // find the fractional distance along the link path closest to this point
        const path = link.path;
        if (path.geometry === null)
            return;
        const localpt = path.getLocalPoint(last);
        lab.segmentFraction = path.geometry.getFractionForPoint(localpt);
    }
}