private int merge(Polygon c1, Polygon c2) {
int x, y, total, d;
Polyline lower, upper, b;
x = y = total = 0;
upper = c1.lower_head;
lower = c2.upper_head;
while (lower != null && upper != null) {
d = offset(x, y, lower.dx, lower.dy, upper.dx, upper.dy);
x += d;
total += d;
if (y + lower.dy <= upper.dy) {
x += lower.dx;
y += lower.dy;
lower = lower.link;
} else {
x -= upper.dx;
y -= upper.dy;
upper = upper.link;
}
}
if (lower != null) {
b = bridge(c1.upper_tail, 0, 0, lower, x, y);
c1.upper_tail = (b.link != null) ? c2.upper_tail : b;
c1.lower_tail = c2.lower_tail;
} else {
b = bridge(c2.lower_tail, x, y, upper, 0, 0);
if (b.link == null) {
c1.lower_tail = b;
}
}
c1.lower_head = c2.lower_head;
return total;
}
