/**
* Compute the position of a sprite if attached to an edge.
*
* @param sprite The sprite.
* @param pos Where to stored the computed position, if null, the position is created.
* @param units The units the computed position must be given into.
* @return The same instance as pos, or a new one if pos was null.
*/
protected Point2D.Double getSpritePositionEdge(
GraphicSprite sprite, Point2D.Double pos, Units units) {
if (pos == null) pos = new Point2D.Double();
GraphicEdge edge = sprite.getEdgeAttachment();
if (edge.isCurve()) {
double ctrl[] = edge.getControlPoints();
Point2 p0 = new Point2(edge.from.getX(), edge.from.getY());
Point2 p1 = new Point2(ctrl[0], ctrl[1]);
Point2 p2 = new Point2(ctrl[1], ctrl[2]);
Point2 p3 = new Point2(edge.to.getX(), edge.to.getY());
Vector2 perp = CubicCurve.perpendicular(p0, p1, p2, p3, sprite.getX());
double y = metrics.lengthToGu(sprite.getY(), sprite.getUnits());
perp.normalize();
perp.scalarMult(y);
pos.x = CubicCurve.eval(p0.x, p1.x, p2.x, p3.x, sprite.getX()) - perp.data[0];
pos.y = CubicCurve.eval(p0.y, p1.y, p2.y, p3.y, sprite.getX()) - perp.data[1];
} else {
double x = ((GraphicNode) edge.getSourceNode()).x;
double y = ((GraphicNode) edge.getSourceNode()).y;
double dx = ((GraphicNode) edge.getTargetNode()).x - x;
double dy = ((GraphicNode) edge.getTargetNode()).y - y;
double d = sprite.getX(); // Percent on the edge.
double o = metrics.lengthToGu(sprite.getY(), sprite.getUnits());
// Offset from the position given by percent, perpendicular to the
// edge.
d = d > 1 ? 1 : d;
d = d < 0 ? 0 : d;
x += dx * d;
y += dy * d;
d = (double) Math.sqrt(dx * dx + dy * dy);
dx /= d;
dy /= d;
x += -dy * o;
y += dx * o;
pos.x = x;
pos.y = y;
if (units == Units.PX) {
Tx.transform(pos, pos);
}
}
return pos;
}