update 2geom (r1350)

(bzr r5999)

3 files changed, 19 insertions, 1 deletions

diff --git a/src/2geom/curve.h b/src/2geom/curve.h
index 7f138dabf..22d2ec556 100644
--- a/src/2geom/curve.h
+++ b/src/2geom/curve.h
@@ -111,6 +111,23 @@ public:
    *  [ point at t, 1st derivative at t, 2nd derivative at t, ... , n'th derivative at t] */
   virtual std::vector<Point> pointAndDerivatives(Coord t, unsigned n) const = 0;
 
+  /* unitTangentAt returns the unit vector tangent to the curve at position t
+   * (in the direction of increasing t). The method uses l'Hopital's rule when the derivative
+   * is (0,0), parameter n determines the maximum nr of iterations (for when higher derivatives are also (0,0) ).
+   * Point(0,0) is returned if no non-zero derivative could be found. */
+  virtual Point unitTangentAt(Coord t, unsigned n = 3) const
+  {
+    for (unsigned deriv_n = 1; deriv_n <= n; deriv_n++) {
+      Point deriv = pointAndDerivatives(t, deriv_n)[deriv_n];
+      Coord length = deriv.length();
+      if ( ! are_near(length, 0) ) {
+         // length of derivative is non-zero, so return unit vector
+         return deriv / length;
+      }
+    }
+    return Point (0,0);
+  };
+
   virtual D2<SBasis> toSBasis() const = 0;
 };
 
diff --git a/src/2geom/transforms.cpp b/src/2geom/transforms.cpp
index b2f305d18..62b340221 100644
--- a/src/2geom/transforms.cpp
+++ b/src/2geom/transforms.cpp
@@ -46,6 +46,7 @@ Matrix operator*(Matrix const &m, Scale const &s) {
 }
 
 Matrix operator*(Matrix const &m, Rotate const &r) {
+    // TODO: we just convert the Rotate to a matrix and use the existing operator*(); is there a better way?
     Matrix ret(m);
     ret *= (Matrix) r;
     return ret;
diff --git a/src/2geom/transforms.h b/src/2geom/transforms.h
index 0e276bfc2..fb077a910 100644
--- a/src/2geom/transforms.h
+++ b/src/2geom/transforms.h
@@ -82,7 +82,7 @@ class Rotate {
     explicit Rotate(Coord theta) : vec(std::cos(theta), std::sin(theta)) {}
     Rotate(Point const &p) {Point v = p; v.normalize(); vec = v;} //TODO: UGLY!
     explicit Rotate(Coord x, Coord y) { Rotate(Point(x, y)); }
-    inline operator Matrix() const { return Matrix(vec[X], -vec[Y], vec[Y], vec[X], 0, 0); }
+    inline operator Matrix() const { return Matrix(vec[X], vec[Y], -vec[Y], vec[X], 0, 0); }
 
     inline Coord operator[](Dim2 const dim) const { return vec[dim]; }
     inline Coord operator[](unsigned const dim) const { return vec[dim]; }