circpos.c

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/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/
 
 
#include "config.h"
/* TODO:
 * If cut point is in exactly 2 blocks, expand block circles to overlap
 * especially in the case where one block is the sole child of the other.
 */
 
#include        <circogen/blockpath.h>
#include        <circogen/circpos.h>
#include        <circogen/nodelist.h>
#include        <math.h>
#include        <stddef.h>
#include        <util/alloc.h>
 
/* The function determines how much the block should be rotated
 * for best positioning with parent, assuming its center is at x and y
 * relative to the parent.
 * angle gives the angle of the new position, i.e., tan(angle) = y/x.
 * If sn has 2 nodes, we arrange the line of the 2 normal to angle.
 * If sn has 1 node, parent_pos has already been set to the 
 * correct angle assuming no rotation.
 * Otherwise, we find the node in sn connected to the parent and rotate
 * the block so that it is closer or at least visible to its node in the
 * parent.
 *
 * For COALESCED blocks, if neighbor is in left half plane, 
 * use unCOALESCED case.
 * Else let theta be angle, R = LEN(x,y), pho the radius of actual 
 * child block, phi be angle of neighbor in actual child block,
 * and r the distance from center of coalesced block to center of 
 * actual block. Then, the angle to rotate the coalesced block to
 * that the edge from the parent is tangent to the neighbor on the
 * actual child block circle is
 *    alpha = theta + M_PI/2 - phi - arcsin((l/R)*(sin B))
 * where l = r - rho/(cos phi) and beta = M_PI/2 + phi.
 * Thus, 
 *    alpha = theta + M_PI/2 - phi - arcsin((l/R)*(cos phi))
 */
static double getRotation(block_t *sn, double x, double y, double theta) {
    double mindist2;
    Agraph_t *subg;
    Agnode_t *n, *closest_node, *neighbor;
    double len2, newX, newY;
 
    subg = sn->sub_graph;
 
    nodelist_t *list = &sn->circle_list;
 
    if (sn->parent_pos >= 0) {
        theta += M_PI - sn->parent_pos;
        if (theta < 0)
            theta += 2 * M_PI;
 
        return theta;
    }
 
    size_t count = nodelist_size(list);
    if (count == 2) {
        return theta - M_PI / 2.0;
    }
 
    /* Find node in block connected to block's parent */
    neighbor = CHILD(sn);
    newX = ND_pos(neighbor)[0] + x;
    newY = ND_pos(neighbor)[1] + y;
    mindist2 = LEN2(newX, newY);    /* save sqrts by using sqr of dist to find min */
    closest_node = neighbor;
 
    for (n = agfstnode(subg); n; n = agnxtnode(subg, n)) {
        if (n == neighbor)
            continue;
 
        newX = ND_pos(n)[0] + x;
        newY = ND_pos(n)[1] + y;
 
        len2 = LEN2(newX, newY);
        if (len2 < mindist2) {
            mindist2 = len2;
            closest_node = n;
        }
    }
 
    if (neighbor != closest_node) {
        double rho = sn->rad0;
        double r = sn->radius - rho;
        double n_x = ND_pos(neighbor)[0];
        if (COALESCED(sn) && -r < n_x) {
            const double R = hypot(x, y);
            double n_y = ND_pos(neighbor)[1];
            double phi = atan2(n_y, n_x + r);
            double l = r - rho / cos(phi);
 
            theta += M_PI / 2.0 - phi - asin(l / R * cos(phi));
        } else {                /* Origin still at center of this block */
            double phi = atan2(ND_pos(neighbor)[1], ND_pos(neighbor)[0]);
            theta += M_PI - phi - PSI(neighbor);
            if (theta > 2 * M_PI)
                theta -= 2 * M_PI;
        }
    } else
        theta = 0;
    return theta;
}
 
/* Recursively apply rotation rotate followed by translation (x,y)
 * to block sn and its children.
 */
static void applyDelta(block_t * sn, double x, double y, double rotate)
{
    block_t *child;
    Agraph_t *subg;
    Agnode_t *n;
 
    subg = sn->sub_graph;
 
    for (n = agfstnode(subg); n; n = agnxtnode(subg, n)) {
 
        const double tmpX = ND_pos(n)[0];
        const double tmpY = ND_pos(n)[1];
        const double cosR = cos(rotate);
        const double sinR = sin(rotate);
 
        const double X = tmpX * cosR - tmpY * sinR;
        const double Y = tmpX * sinR + tmpY * cosR;
 
        /* translate */
        ND_pos(n)[0] = X + x;
        ND_pos(n)[1] = Y + y;
    }
 
    for (child = sn->children.first; child; child = child->next)
        applyDelta(child, x, y, rotate);
}
 
/* firstangle and lastangle give the range of child angles.
 * These are set and used only when a block has just 1 node.
 * And are used to give the center angle between the two extremes.
 * The parent will then be attached at PI - center angle (parent_pos).
 * If this block has no children, this is PI. Otherwise, positionChildren will
 * be called once with the blocks node. firstangle will be 0, with
 * succeeding angles increasing. 
 * position can always return the center angle - PI, since the block
 * must have children and if the block has 1 node, the limits will be
 * correctly set. If the block has more than 1 node, the value is
 * unused.
 */
typedef struct {
    double radius;              /* Basic radius of block */
    double subtreeR;            /* Max of subtree radii */
    double nodeAngle;           /* Angle allocated to each node in block */
    double firstAngle;          /* Smallest child angle when block has 1 node */
    double lastAngle;           /* Largest child angle when block has 1 node */
    block_t *cp;                /* Children of block */
    node_t *neighbor;           /* Node connected to parent block, if any */
} posstate;
 
typedef struct {
    Agnode_t* n;
    double theta;        /* angle of node */
    double minRadius;    /* minimum radius for child circle */
    double maxRadius;    /* maximum radius of child blocks */
    double diameter;     /* length of arc needed for child blocks */
    double scale;        /* scale factor to increase minRadius to parents' children don't overlap */
    int childCount;      /* no. of child blocks attached at n */
} posinfo_t;
 
static double
getInfo (posinfo_t* pi, posstate * stp, double min_dist)
{
    block_t *child;
    double maxRadius = 0;       /* Max. radius of children */
    double diameter = 0;        /* sum of child diameters */
    int childCount = 0;
 
    for (child = stp->cp; child; child = child->next) {
        if (BLK_PARENT(child) == pi->n) {
            childCount++;
            maxRadius = fmax(maxRadius, child->radius);
            diameter += 2 * child->radius + min_dist;
        }
    }
 
    pi->diameter = diameter;
    pi->childCount = childCount;
    pi->minRadius = stp->radius + min_dist + maxRadius;
    pi->maxRadius = maxRadius;
    return maxRadius;
}
 
static void
setInfo (posinfo_t* p0, posinfo_t* p1, double delta)
{
    double t = p0->diameter * p1->minRadius + p1->diameter * p0->minRadius;
 
    t /= 2*delta*p0->minRadius*p1->minRadius;
 
    t = fmax(t, 1);
 
    p0->scale = fmax(p0->scale, t);
    p1->scale = fmax(p1->scale, t);
}
 
static void positionChildren(posinfo_t *info, posstate *stp, size_t length,
                             double min_dist) {
    block_t *child;
    double childAngle, childRadius, incidentAngle;
    double mindistAngle, rotateAngle, midAngle = 0.0;
    int midChild, cnt = 0;
    double snRadius = stp->subtreeR;    /* max subtree radius */
    double firstAngle = stp->firstAngle;
    double lastAngle = stp->lastAngle;
    double d, deltaX, deltaY;
 
    childRadius = info->scale * info->minRadius;
    if (length == 1) {
        childAngle = 0;
        d = info->diameter / (2 * M_PI);
        childRadius = fmax(childRadius, d);
        d = 2 * M_PI * childRadius - info->diameter;
        if (d > 0)
            min_dist += d / info->childCount;
    }
    else
        childAngle = info->theta - info->diameter / (2 * childRadius);
 
    snRadius = fmax(snRadius, childRadius + info->maxRadius);
 
    mindistAngle = min_dist / childRadius;
 
    midChild = (info->childCount + 1) / 2;
    for (child = stp->cp; child; child = child->next) {
        if (BLK_PARENT(child) != info->n)
            continue;
        if (nodelist_is_empty(&child->circle_list))
            continue;
 
        incidentAngle = child->radius / childRadius;
        if (length == 1) {
            if (childAngle != 0) {
                if (info->childCount == 2)
                    childAngle = M_PI;
                else
                    childAngle += incidentAngle;
            }
 
            if (firstAngle < 0)
                firstAngle = childAngle;
 
            lastAngle = childAngle;
        } else {
            if (info->childCount == 1) {
                childAngle = info->theta;
            } else {
                childAngle += incidentAngle + mindistAngle / 2;
            }
        }
 
        deltaX = childRadius * cos(childAngle);
        deltaY = childRadius * sin(childAngle);
 
        /* first apply the delta to the immediate child and see if we need
         * to rotate it for better edge link                                            
         * should return the theta value if there was a rotation else zero
         */
 
        rotateAngle = getRotation(child, deltaX, deltaY, childAngle);
        applyDelta(child, deltaX, deltaY, rotateAngle);
 
        if (length == 1) {
            childAngle += incidentAngle + mindistAngle;
        } else {
            childAngle += incidentAngle + mindistAngle / 2;
        }
        cnt++;
        if (cnt == midChild)
            midAngle = childAngle;
    }
 
    if (length > 1 && info->n == stp->neighbor) {
        PSI(info->n) = midAngle;
    }
 
    stp->subtreeR = snRadius;
    stp->firstAngle = firstAngle;
    stp->lastAngle = lastAngle;
}
 
/* Assume childCount > 0
 * For each node in the block with children, getInfo is called, with the
 * information stored in the parents array.
 * This information is used by setInfo to compute the amount of space allocated
 * to each parent and the radius at which to place its children.
 * Finally, positionChildren is called to do the actual positioning.
 * If length is 1, keeps track of minimum and maximum child angle.
 */
static double position(size_t childCount, size_t length, nodelist_t *nodepath,
         block_t * sn, double min_dist)
{
    posstate state;
    int i, counter = 0;
    double maxRadius = 0.0;
    double angle;
    double theta = 0.0;
    posinfo_t* parents = gv_calloc(childCount, sizeof(posinfo_t));
    int num_parents = 0;
    posinfo_t* next;
    posinfo_t* curr;
    double delta;
 
    state.cp = sn->children.first;
    state.subtreeR = sn->radius;
    state.radius = sn->radius;
    state.neighbor = CHILD(sn);
    state.nodeAngle = 2 * M_PI / (double)length;
    state.firstAngle = -1;
    state.lastAngle = -1;
 
    for (size_t item = 0; item < nodelist_size(nodepath); ++item) {
        Agnode_t *n = nodelist_get(nodepath, item);
 
        theta = counter * state.nodeAngle;
        counter++;
 
        if (ISPARENT(n)) {
            parents[num_parents].n = n;
            parents[num_parents].theta = theta;
            maxRadius = getInfo (parents+num_parents, &state, min_dist);
            num_parents++;
        }
    }
 
    if (num_parents == 1)
        parents->scale = 1.0;
    else if (num_parents == 2) {
        curr = parents;
        next = parents+1;
        delta = next->theta - curr->theta;
        if (delta > M_PI)
            delta = 2*M_PI - delta;
        setInfo (curr, next, delta);
    }
    else {
        curr = parents;
        for (i = 0; i < num_parents; i++) {
            if (i+1 == num_parents) {
                next = parents;
                delta = next->theta - curr->theta + 2*M_PI; 
            }
            else {
                next = curr+1;
                delta = next->theta - curr->theta; 
            }
            setInfo (curr, next, delta);
            curr++;
        }
    }
 
    for (i = 0; i < num_parents; i++) {
        positionChildren(parents + i, &state, length, min_dist);
    }
 
    free (parents);
 
    /* If block has only 1 child, to save space, we coalesce it with the
     * child. Instead of having final radius sn->radius + max child radius,
     * we have half that. However, the origin of the block is no longer in
     * the center of the block, so we cannot do a simple rotation to get
     * the neighbor node next to the parent block in getRotate.
     */
    if (childCount == 1) {
        applyDelta(sn, -(maxRadius + min_dist / 2), 0, 0);
        sn->radius += min_dist / 2 + maxRadius;
        SET_COALESCED(sn);
    } else
        sn->radius = state.subtreeR;
 
    angle = (state.firstAngle + state.lastAngle) / 2.0 - M_PI;
    return angle;
}
 
static void doBlock(Agraph_t *g, block_t *sn, double min_dist,
                    circ_state *state) {
    block_t *child;
    double centerAngle = M_PI;
 
    /* layout child subtrees */
    size_t childCount = 0;
    for (child = sn->children.first; child; child = child->next) {
        doBlock(g, child, min_dist, state);
        childCount++;
    }
 
    /* layout this block */
    nodelist_t longest_path = layout_block(g, sn, min_dist, state);
    sn->circle_list = longest_path;
    size_t length = nodelist_size(&longest_path); // path contains everything in block
 
    /* attach children */
    if (childCount > 0)
        centerAngle = position(childCount, length, &longest_path, sn, min_dist);
 
    if (length == 1 && BLK_PARENT(sn)) {
        sn->parent_pos = centerAngle;
        if (sn->parent_pos < 0)
            sn->parent_pos += 2 * M_PI;
    }
}
 
void circPos(Agraph_t * g, block_t * sn, circ_state * state)
{
  doBlock(g, sn, state->min_dist, state);
}