ParallelLayout.js

/*
 *  Copyright 1998-2025 by Northwoods Software Corporation. All Rights Reserved.
 */
/*
 * This is an extension and not part of the main GoJS library.
 * The source code for this is at extensionsJSM/ParallelLayout.ts.
 * 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 extensionsJSM folders.
 * See the Extensions intro page (https://gojs.net/latest/intro/extensions.html) for more information.
 */

/**
 * A custom {@link go.TreeLayout} that can be used for laying out stylized flowcharts.
 * Each layout requires a single 'Split' node and a single 'Merge' node.
 * The 'Split' node should be the root of a tree-like structure if one excludes links to the 'Merge' node.
 * This will position the 'Merge' node to line up with the 'Split' node.
 *
 * You can set all of the TreeLayout properties that you like,
 * except that for simplicity this code just works for angle === 0 or angle === 90.
 *
 * If you want to experiment with this extension, try the <a href="../../samples/Parallel.html">Parallel Layout</a> sample.
 * @category Layout Extension
 */
class ParallelLayout extends go.TreeLayout {
    /**
     * Constructs a ParallelLayout and sets the following properties:
     *   - {@link isRealtime} = false
     *   - {@link alignment} = {@link go.TreeAlignment.CenterChildren}
     *   - {@link compaction} = {@link go.TreeCompaction.None}
     *   - {@link alternateAlignment} = {@link go.TreeAlignment.CenterChildren}
     *   - {@link alternateCompaction} = {@link go.TreeCompaction.None}
     */
    constructor(init) {
        super();
        this.isRealtime = false;
        this.alignment = go.TreeAlignment.CenterChildren;
        this.compaction = go.TreeCompaction.None;
        this.alternateAlignment = go.TreeAlignment.CenterChildren;
        this.alternateCompaction = go.TreeCompaction.None;
        this._splitNode = null;
        this._mergeNode = null;
        if (init)
            Object.assign(this, init);
    }
    /**
     * This read-only property returns the node that the tree will extend from.
     */
    get splitNode() {
        return this._splitNode;
    }
    set splitNode(val) {
        if (val !== null && !(val instanceof go.Node))
            throw new Error('ParallelLayout.splitNode must be a go.Node');
        this._splitNode = val;
    }
    /**
     * This read-only property returns the node that the tree will converge at.
     */
    get mergeNode() {
        return this._mergeNode;
    }
    set mergeNode(val) {
        if (val !== null && !(val instanceof go.Node))
            throw new Error('ParallelLayout.mergeNode must be a go.Node');
        this._mergeNode = val;
    }
    /**
     * Overridable predicate for deciding if a Node is a Split node.
     * By default this checks the node's {@link go.Part.category} to see if it is
     * 'Split', 'Start', 'For', 'While', 'If', or 'Switch'.
     * @param node
     */
    isSplit(node) {
        if (!(node instanceof go.Node))
            return false;
        const cat = node.category;
        return (cat === 'Split' ||
            cat === 'Start' ||
            cat === 'For' ||
            cat === 'While' ||
            cat === 'If' ||
            cat === 'Switch');
    }
    /**
     * Overridable predicate for deciding if a Node is a Merge node.
     * By default this checks the node's {@link go.Part.category} to see if it is
     * 'Merge', 'End', 'EndFor', 'EndWhile', 'EndIf', or 'EndSwitch'.
     * @param node
     */
    isMerge(node) {
        if (!(node instanceof go.Node))
            return false;
        const cat = node.category;
        return (cat === 'Merge' ||
            cat === 'End' ||
            cat === 'EndFor' ||
            cat === 'EndWhile' ||
            cat === 'EndIf' ||
            cat === 'EndSwitch');
    }
    /**
     * Overridable predicate for deciding if a Node is a conditional or 'If' type of Split Node
     * expecting to have two links coming out of the sides.
     * @param node
     */
    isConditional(node) {
        if (!(node instanceof go.Node))
            return false;
        return node.category === 'If';
    }
    /**
     * Overridable predicate for deciding if a Node is a 'Switch' type of Split Node
     * expecting to have three links coming out of the bottom/right side.
     * @param node
     */
    isSwitch(node) {
        if (!(node instanceof go.Node))
            return false;
        return node.category === 'Switch';
    }
    /**
     * Find a Split vertex and a Merge vertex for this layout.
     * This signals an error if there is not exactly one vertex/Node that {@link isSplit}
     * and exactly one vertex/Node that {@link isMerge}.
     * This can be overridden; any override must set {@link splitNode} and {@link mergeNode}.
     * @param vertexes
     */
    findSplitMerge(vertexes) {
        let split = null;
        let merge = null;
        const it = vertexes.iterator;
        while (it.next()) {
            const v = it.value;
            if (!v.node)
                continue;
            if (this.isSplit(v.node)) {
                if (split)
                    throw new Error('Split node already exists in ' + this + ' -- existing: ' + split + ' new: ' + v.node);
                split = v.node;
            }
            else if (this.isMerge(v.node)) {
                if (merge)
                    throw new Error('Merge node already exists in ' + this + ' -- existing: ' + merge + ' new: ' + v.node);
                merge = v.node;
            }
        }
        if (!split)
            throw new Error('Missing Split node in ' + this);
        if (!merge)
            throw new Error('Missing Merge node in ' + this);
        this._splitNode = split;
        this._mergeNode = merge;
    }
    /**
     * @hidden @internal
     */
    makeNetwork(coll) {
        const net = super.makeNetwork(coll);
        // Groups might be unbalanced -- position them so that the Split node is centered under the parent node.
        const it = net.vertexes.iterator;
        while (it.next()) {
            const v = it.value;
            const g = v.node;
            if (g instanceof go.Group &&
                g.isSubGraphExpanded &&
                g.placeholder &&
                g.placeholder.visible &&
                g.layout instanceof ParallelLayout) {
                const split = g.layout.splitNode;
                if (split) {
                    if (this.angle === 0) {
                        v.focusY = split.location.y - g.position.y;
                    }
                    else if (this.angle === 90) {
                        v.focusX = split.location.x - g.position.x;
                    }
                }
            }
        }
        if (this.group && !this.group.isSubGraphExpanded)
            return net;
        // look for and remember the one Split node and the one Merge node
        this.findSplitMerge(net.vertexes.iterator);
        // don't have TreeLayout lay out the Merge node; commitNodes will do it
        if (this.mergeNode)
            net.deleteNode(this.mergeNode);
        // for each vertex that does not have an incoming edge,
        // connect to it from the splitNode vertex with a dummy edge
        if (this.splitNode) {
            const splitv = net.findVertex(this.splitNode);
            net.vertexes.each((v) => {
                if (splitv === null || v === splitv)
                    return;
                if (v.sourceEdges.count === 0) {
                    net.linkVertexes(splitv, v, null);
                }
            });
        }
        return net;
    }
    /**
     * @hidden @internal
     */
    commitNodes() {
        super.commitNodes();
        // Line up the Merge node to the center of the Split node
        const mergeNode = this.mergeNode;
        const splitNode = this.splitNode;
        if (mergeNode === null || splitNode === null || this.network === null)
            return;
        const splitVertex = this.network.findVertex(splitNode);
        if (splitVertex === null)
            return;
        if (this.angle === 0) {
            mergeNode.location = new go.Point(splitVertex.x +
                splitVertex.subtreeSize.width +
                this.layerSpacing +
                mergeNode.actualBounds.width / 2, splitVertex.centerY);
        }
        else if (this.angle === 90) {
            mergeNode.location = new go.Point(splitVertex.centerX, splitVertex.y +
                splitVertex.subtreeSize.height +
                this.layerSpacing +
                mergeNode.actualBounds.height / 2);
        }
        mergeNode.ensureBounds();
    }
    /**
     * @hidden @internal
     */
    commitLinks() {
        const splitNode = this.splitNode;
        const mergeNode = this.mergeNode;
        if (splitNode === null || mergeNode === null || this.network === null)
            return;
        // set default link spots based on this.angle
        const it = this.network.edges.iterator;
        while (it.next()) {
            const e = it.value;
            const link = e.link;
            if (!link)
                continue;
            if (this.angle === 0) {
                if (this.setsPortSpot)
                    link.fromSpot = go.Spot.Right;
                if (this.setsChildPortSpot)
                    link.toSpot = go.Spot.Left;
            }
            else if (this.angle === 90) {
                if (this.setsPortSpot)
                    link.fromSpot = go.Spot.Bottom;
                if (this.setsChildPortSpot)
                    link.toSpot = go.Spot.Top;
            }
        }
        // Make sure links coming into and going out of a Split node come in the correct way
        if (splitNode) {
            // Handle links coming into the Split node
            const cond = this.isConditional(splitNode);
            const swtch = this.isSwitch(splitNode);
            // Handle links going out of the Split node
            let first = true; // handle 'If' nodes specially
            const lit = splitNode.findLinksOutOf();
            while (lit.next()) {
                const link = lit.value;
                if (this.angle === 0) {
                    if (this.setsPortSpot) {
                        link.fromSpot = cond
                            ? first
                                ? go.Spot.Top
                                : go.Spot.Bottom
                            : swtch
                                ? go.Spot.RightSide
                                : go.Spot.Right;
                    }
                    if (this.setsChildPortSpot)
                        link.toSpot = go.Spot.Left;
                }
                else if (this.angle === 90) {
                    if (this.setsPortSpot) {
                        link.fromSpot = cond
                            ? first
                                ? go.Spot.Left
                                : go.Spot.Right
                            : swtch
                                ? go.Spot.BottomSide
                                : go.Spot.Bottom;
                    }
                    if (this.setsChildPortSpot)
                        link.toSpot = go.Spot.Top;
                }
                first = false;
            }
        }
        if (mergeNode) {
            // Handle links going into the Merge node
            const iit = mergeNode.findLinksInto();
            while (iit.next()) {
                const link = iit.value;
                if (!this.isSplit(link.fromNode)) {
                    // if link connects Split with Merge directly, only set fromSpot once
                    if (this.angle === 0) {
                        if (this.setsPortSpot)
                            link.fromSpot = go.Spot.Right;
                        if (this.setsChildPortSpot)
                            link.toSpot = go.Spot.Left;
                    }
                    else if (this.angle === 90) {
                        if (this.setsPortSpot)
                            link.fromSpot = go.Spot.Bottom;
                        if (this.setsChildPortSpot)
                            link.toSpot = go.Spot.Top;
                    }
                }
                if (!link.isOrthogonal)
                    continue;
                // have all of the links coming into the Merge node have segments
                // that share a common X (or if angle==90, Y) coordinate
                link.updateRoute();
                if (link.pointsCount >= 6) {
                    const pts = link.points.copy();
                    const p2 = pts.elt(pts.length - 4);
                    const p3 = pts.elt(pts.length - 3);
                    if (this.angle === 0 && p2.x === p3.x && p2.y !== p3.y) {
                        const x = mergeNode.position.x - this.layerSpacing / 2;
                        pts.setElt(pts.length - 4, new go.Point(x, p2.y));
                        pts.setElt(pts.length - 3, new go.Point(x, p3.y));
                    }
                    else if (this.angle === 90 && p2.y === p3.y && p2.x !== p3.x) {
                        const y = mergeNode.position.y - this.layerSpacing / 2;
                        pts.setElt(pts.length - 4, new go.Point(p2.x, y));
                        pts.setElt(pts.length - 3, new go.Point(p3.x, y));
                    }
                    link.points = pts;
                }
            }
            // handle links coming out of the Merge node, looping back left/up
            const oit = mergeNode.findLinksOutOf();
            while (oit.next()) {
                const link = oit.value;
                // if connects internal with external node, it isn't a loop-back link
                if (link.toNode && link.toNode.containingGroup !== mergeNode.containingGroup)
                    continue;
                if (this.angle === 0) {
                    if (this.setsPortSpot)
                        link.fromSpot = go.Spot.TopBottomSides;
                    if (this.setsChildPortSpot)
                        link.toSpot = go.Spot.TopBottomSides;
                }
                else if (this.angle === 90) {
                    if (this.setsPortSpot)
                        link.fromSpot = go.Spot.LeftRightSides;
                    if (this.setsChildPortSpot)
                        link.toSpot = go.Spot.LeftRightSides;
                }
                link.routing = go.Routing.AvoidsNodes;
            }
        }
    }
}