src/libnr/nr-types.cpp

   1 /** \file
   2  * Implements NR::Point::normalize()
   3  */
   4
   5 #include <libnr/nr-types.h>
   6
   7 #include "2geom/isnan.h"
   8
   9 /** Scales this vector to make it a unit vector (within rounding error).
  10  *
  11  *  The current version tries to handle infinite coordinates gracefully,
  12  *  but it's not clear that any callers need that.
  13  *
  14  *  \pre *this != Point(0, 0).
  15  *  \pre Neither coordinate is NaN.
  16  *  \post L2(*this) very near 1.0.
  17  */
  18 void NR::Point::normalize() {
  19         double len = hypot(_pt[0], _pt[1]);
  20         g_return_if_fail(len != 0);
  21         g_return_if_fail(!IS_NAN(len));
  22         static double const inf = 1e400;
  23         if(len != inf) {
  24                 *this /= len;
  25         } else {
  26                 unsigned n_inf_coords = 0;
  27                 /* Delay updating pt in case neither coord is infinite. */
  28                 NR::Point tmp;
  29                 for ( unsigned i = 0 ; i < 2 ; ++i ) {
  30                         if ( _pt[i] == inf ) {
  31                                 ++n_inf_coords;
  32                                 tmp[i] = 1.0;
  33                         } else if ( _pt[i] == -inf ) {
  34                                 ++n_inf_coords;
  35                                 tmp[i] = -1.0;
  36                         } else {
  37                                 tmp[i] = 0.0;
  38                         }
  39                 }
  40                 switch (n_inf_coords) {
  41                 case 0:
  42                         /* Can happen if both coords are near +/-DBL_MAX. */
  43                         *this /= 4.0;
  44                         len = hypot(_pt[0], _pt[1]);
  45                         g_assert(len != inf);
  46                         *this /= len;
  47                         break;
  48
  49                 case 1:
  50                         *this = tmp;
  51                         break;
  52
  53                 case 2:
  54                         *this = sqrt(0.5) * tmp;
  55                         break;
  56                 }
  57         }
  58 }
  59 /*
  60   Local Variables:
  61   mode:c++
  62   c-file-style:"stroustrup"
  63   c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
  64   indent-tabs-mode:nil
  65   fill-column:99
  66   End:
  67 */
  68 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :