in pytheas-core/src/main/resources/js/d3/d3.layout.js [1209:1299]
function d3_layout_packCircle(nodes) {
var xMin = Infinity,
xMax = -Infinity,
yMin = Infinity,
yMax = -Infinity,
n = nodes.length,
a, b, c, j, k;
function bound(node) {
xMin = Math.min(node.x - node.r, xMin);
xMax = Math.max(node.x + node.r, xMax);
yMin = Math.min(node.y - node.r, yMin);
yMax = Math.max(node.y + node.r, yMax);
}
// Create node links.
nodes.forEach(d3_layout_packLink);
// Create first node.
a = nodes[0];
a.x = -a.r;
a.y = 0;
bound(a);
// Create second node.
if (n > 1) {
b = nodes[1];
b.x = b.r;
b.y = 0;
bound(b);
// Create third node and build chain.
if (n > 2) {
c = nodes[2];
d3_layout_packPlace(a, b, c);
bound(c);
d3_layout_packInsert(a, c);
a._pack_prev = c;
d3_layout_packInsert(c, b);
b = a._pack_next;
// Now iterate through the rest.
for (var i = 3; i < n; i++) {
d3_layout_packPlace(a, b, c = nodes[i]);
// Search for the closest intersection.
var isect = 0, s1 = 1, s2 = 1;
for (j = b._pack_next; j !== b; j = j._pack_next, s1++) {
if (d3_layout_packIntersects(j, c)) {
isect = 1;
break;
}
}
if (isect == 1) {
for (k = a._pack_prev; k !== j._pack_prev; k = k._pack_prev, s2++) {
if (d3_layout_packIntersects(k, c)) {
break;
}
}
}
// Update node chain.
if (isect) {
if (s1 < s2 || (s1 == s2 && b.r < a.r)) d3_layout_packSplice(a, b = j);
else d3_layout_packSplice(a = k, b);
i--;
} else {
d3_layout_packInsert(a, c);
b = c;
bound(c);
}
}
}
}
// Re-center the circles and return the encompassing radius.
var cx = (xMin + xMax) / 2,
cy = (yMin + yMax) / 2,
cr = 0;
for (var i = 0; i < n; i++) {
var node = nodes[i];
node.x -= cx;
node.y -= cy;
cr = Math.max(cr, node.r + Math.sqrt(node.x * node.x + node.y * node.y));
}
// Remove node links.
nodes.forEach(d3_layout_packUnlink);
return cr;
}