/// <summary>
/// Gets the point on this line that is closest to a specified position.
/// </summary>
/// <param name="p">The position to search from.</param>
/// <param name="tol">Maximum distance from line to the search position</param>
/// <returns>The closest position (null if the line is further away than the specified
/// max distance)</returns>
internal override IPosition GetClosest(IPointGeometry p, ILength tol)
{
// Get the distance from the centre of the circle to the search point.
IPointGeometry center = m_Circle.Center;
double dist = Geom.Distance(center, p);
// Return if the search point is beyond tolerance.
double radius = m_Circle.Radius;
double diff = Math.Abs(dist - radius);
if (diff > tol.Meters)
{
return(null);
}
// If the vertex lies in the curve sector, the closest position
// is along the bearing from the centre through the search
// position. Otherwise the closest position is the end of
// the curve that's closest (given that it's within tolerance).
if (CircularArcGeometry.IsInSector(this, p, 0.0))
{
double bearing = Geom.BearingInRadians(center, p);
return(Geom.Polar(center, bearing, radius));
}
double d1 = Geom.DistanceSquared(p, BC);
double d2 = Geom.DistanceSquared(p, EC);
double t = tol.Meters;
if (Math.Min(d1, d2) < (t * t))
{
if (d1 < d2)
{
return(BC);
}
else
{
return(EC);
}
}
return(null);
}
/// <summary>
/// Cuts back a horizontal line segment to the closest intersection with this line.
/// Used in point in polygon.
/// </summary>
/// <param name="s">Start of horizontal segment.</param>
/// <param name="e">End of segment (will be modified if segment intersects this line)</param>
/// <param name="status">Return code indicating whether an error has arisen (returned
/// as 0 if no error).</param>
/// <returns>True if the horizontal line was cut back.</returns>
internal override bool GetCloser(IPointGeometry s, ref PointGeometry e, out uint status)
{
status = 0;
// Get the window of the circle that this curve lies on.
IWindow cwin = m_Circle.Extent;
// Get a window for the horizontal segment.
IWindow segwin = new Window(s, e);
// Return if the windows don't overlap.
if (!cwin.IsOverlap(segwin))
{
return(false);
}
// Return if the the segment is to the west of the circle's window.
if (segwin.Max.X < cwin.Min.X)
{
return(false);
}
// Represent the horizontal segment in a class of its own
HorizontalRay hseg = new HorizontalRay(s, e.X - s.X);
if (!hseg.IsValid)
{
status = 1;
return(false);
}
// Locate up to two intersections of the horizontal segment with the circle.
IPosition x1 = null;
IPosition x2 = null;
uint nx = hseg.Intersect(m_Circle, ref x1, ref x2);
// Return if no intersections
if (nx == 0)
{
return(false);
}
// Return if this arc curve is a complete circle.
if (this.IsCircle)
{
return(false);
}
// Check whether the first intersection lies on this arc. If
// so, update the end of segment, and return.
if (CircularArcGeometry.IsInSector(this, x1, 0.0))
{
e = new PointGeometry(x1);
return(true);
}
// If we got two intersections with the circle, check the
// second intersection as well.
if (nx == 2 && CircularArcGeometry.IsInSector(this, x2, 0.0))
{
e = new PointGeometry(x2);
return(true);
}
return(false);
}
