modules/actions/straighten_nodes.js

import { geoGetSmallestSurroundingRectangle, geoVecDot, geoVecLength, geoVecInterp } from '../geo';


/* Align nodes along their common axis */
export function actionStraightenNodes(nodeIDs, projection) {

    function positionAlongWay(a, o, b) {
        return geoVecDot(a, b, o) / geoVecDot(b, b, o);
    }


    var action = function(graph, t) {
        if (t === null || !isFinite(t)) t = 1;
        t = Math.min(Math.max(+t, 0), 1);

        var nodes = nodeIDs.map(function(id) { return graph.entity(id); });
        var points = nodes.map(function(n) { return projection(n.loc); });
        var ssr = geoGetSmallestSurroundingRectangle(points);

        // Choose line pq = axis of symmetry.
        // The shape's surrounding rectangle has 2 axes of symmetry.
        // Snap points to the long axis
        var p1 = [(ssr.poly[0][0] + ssr.poly[1][0]) / 2, (ssr.poly[0][1] + ssr.poly[1][1]) / 2 ];
        var q1 = [(ssr.poly[2][0] + ssr.poly[3][0]) / 2, (ssr.poly[2][1] + ssr.poly[3][1]) / 2 ];
        var p2 = [(ssr.poly[3][0] + ssr.poly[4][0]) / 2, (ssr.poly[3][1] + ssr.poly[4][1]) / 2 ];
        var q2 = [(ssr.poly[1][0] + ssr.poly[2][0]) / 2, (ssr.poly[1][1] + ssr.poly[2][1]) / 2 ];
        var p, q;

        var isLong = (geoVecLength(p1, q1) > geoVecLength(p2, q2));
        if (isLong) {
            p = p1;
            q = q1;
        } else {
            p = p2;
            q = q2;
        }

        // Move points onto line pq
        for (var i = 0; i < points.length; i++) {
            var node = nodes[i];
            var point = points[i];
            var u = positionAlongWay(point, p, q);
            var point2 = geoVecInterp(p, q, u);
            var loc2 = projection.invert(point2);
            graph = graph.replace(node.move(geoVecInterp(node.loc, loc2, t)));
        }

        return graph;
    };


    action.disabled = function() {
        return false;
    };


    action.transitionable = true;


    return action;
}