Filters. New custom predefined cross-smooth filter (very experimental...).

[inkscape.git] / src / 2geom / curve.h

diff --git a/src/2geom/curve.h b/src/2geom/curve.h
index b76c0d328cdc4fb6defe90142c23a47b816b8c57..65bf86ef6e7570db3f08707e5458e7e1355dcdf4 100644 (file)
--- a/src/2geom/curve.h
+++ b/src/2geom/curve.h
@@ -1,5 +1,6 @@
-/*
- * Abstract Curve Type
+/**
+ * \file
+ * \brief   Abstract Curve Type
  *
  * Authors:
  *             MenTaLguY <mental@rydia.net>
@@ -38,14 +39,14 @@
 #define _2GEOM_CURVE_H_
 
 
-#include "coord.h"
-#include "point.h"
-#include "interval.h"
-#include "nearest-point.h"
-#include "sbasis.h"
-#include "d2.h"
-#include "matrix.h"
-#include "exception.h"
+#include <2geom/coord.h>
+#include <2geom/point.h>
+#include <2geom/interval.h>
+#include <2geom/nearest-point.h>
+#include <2geom/sbasis.h>
+#include <2geom/d2.h>
+#include <2geom/matrix.h>
+#include <2geom/exception.h>
 
 #include <vector>
 
@@ -67,19 +68,23 @@ public:
   virtual Point initialPoint() const = 0;
   virtual Point finalPoint() const = 0;
 
+  /* isDegenerate returns true if the curve has "zero length".
+   * For a bezier curve this means for example that all handles are at the same point */
   virtual bool isDegenerate() const = 0;
 
   virtual Curve *duplicate() const = 0;
 
-  virtual Rect boundsFast() const = 0;
-  virtual Rect boundsExact() const = 0;
-  virtual Rect boundsLocal(Interval i, unsigned deg) const = 0;
-  Rect boundsLocal(Interval i) const { return boundsLocal(i, 0); }
+  virtual OptRect boundsFast() const = 0;
+  virtual OptRect boundsExact() const = 0;
+  virtual OptRect boundsLocal(OptInterval i, unsigned deg) const = 0;
+  OptRect boundsLocal(OptInterval i) const { return boundsLocal(i, 0); }
 
   virtual std::vector<double> roots(double v, Dim2 d) const = 0;
 
   virtual int winding(Point p) const { return root_winding(*this, p); }
 
+  virtual int degreesOfFreedom() const { return 0;}
+
   //mental: review these
   virtual Curve *portion(double f, double t) const = 0;
   virtual Curve *reverse() const { return portion(1, 0); }
@@ -101,14 +106,55 @@ public:
          return all_nearest_points(p, toSBasis(), from, to);
   }
 
+  /*
+  Path operator*=(Matrix)
+  This is not possible, because:
+  A Curve can be many things, for example a HLineSegment.
+  Such a segment cannot be transformed and stay a HLineSegment in general (take for example rotations).
+  This means that these curves become a different type of curve, hence one should use "transformed(Matrix).
+  */
+
   virtual Curve *transformed(Matrix const &m) const = 0;
 
-  virtual Point pointAt(Coord t) const { return pointAndDerivatives(t, 1).front(); }
+  virtual Point pointAt(Coord t) const { return pointAndDerivatives(t, 0).front(); }
   virtual Coord valueAt(Coord t, Dim2 d) const { return pointAt(t)[d]; }
+  virtual Point operator() (double t)  const { return pointAt(t); }
+  
+  /* pointAndDerivatives returns a vector that looks like the following:
+   *  [ 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. 
+   * Note that unitTangentAt(1) will probably not give the desired result. Probably one should do:
+   *    Curve * c_reverse = c.reverse();
+   *    Point tangent = - c_reverse->unitTangentAt(0);
+   *    delete c_reverse;
+   */
+  virtual Point unitTangentAt(Coord t, unsigned n = 3) const
+  {
+    std::vector<Point> derivs = pointAndDerivatives(t, n);
+    for (unsigned deriv_n = 1; deriv_n < derivs.size(); deriv_n++) {
+      Coord length = derivs[deriv_n].length();
+      if ( ! are_near(length, 0) ) {
+         // length of derivative is non-zero, so return unit vector
+         return derivs[deriv_n] / length;
+      }
+    }
+    return Point (0,0);
+  };
+
   virtual D2<SBasis> toSBasis() const = 0;
+  virtual bool operator==(Curve const &c) const { return this == &c;}
 };
 
+inline
+Coord nearest_point(Point const& p, Curve const& c)
+{
+       return c.nearestPoint(p);
+}
 
 } // end namespace Geom
 
@@ -126,4 +172,4 @@ public:
   fill-column:99
   End:
 */
-// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :