GUI functionality fixes.

[architektonas] / src / geometry.cpp

diff --git a/src/geometry.cpp b/src/geometry.cpp
index 4cd229f76da7967d10811ed3ff803a0d46427e92..95d12c65068b16715086191e1d70c7e01483dcbd 100644 (file)
--- a/src/geometry.cpp
+++ b/src/geometry.cpp
@@ -39,6 +39,29 @@ double Geometry::ParameterOfLineAndPoint(Point tail, Point head, Point point)
 }
 
 
+double Geometry::DistanceToLineFromPoint(Point tail, Point head, Point point)
+{
+       // Interpretation: given a line in the form x = a + tu, where u is the
+       // unit vector of the line, a is the tail and t is a parameter which
+       // describes the line, the distance of a point p to the line is given by:
+       // || (a - p) - ((a - p) . u) u ||
+       // We go an extra step: we set the sign to reflect which side of the line
+       // it's on (+ == to the left if head points away from you, - == to the
+       // right)
+       Vector line(tail, head);
+       Vector u = line.Unit();
+       Vector a_p = tail - point;
+       Vector dist = a_p - (u * (a_p).Dot(u));
+
+       double angle = Vector::Angle(tail, point) - line.Angle();
+
+       if (angle < 0)
+               angle += TAU;
+
+       return dist.Magnitude() * (angle < HALF_TAU ? +1.0 : -1.0);
+}
+
+
 Point Geometry::MirrorPointAroundLine(Point point, Point tail, Point head)
 {
        // Get the vector of the intersection of the line and the normal on the