src/Projection/CompareProjection.cpp

   1 /*
   2 Copyright_License {
   3
   4   XCSoar Glide Computer - http://www.xcsoar.org/
   5   Copyright (C) 2000-2013 The XCSoar Project
   6   A detailed list of copyright holders can be found in the file "AUTHORS".
   7
   8   This program is free software; you can redistribute it and/or
   9   modify it under the terms of the GNU General Public License
  10   as published by the Free Software Foundation; either version 2
  11   of the License, or (at your option) any later version.
  12
  13   This program is distributed in the hope that it will be useful,
  14   but WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16   GNU General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with this program; if not, write to the Free Software
  20   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  21 }
  22 */
  23
  24 #include "CompareProjection.hpp"
  25 #include "WindowProjection.hpp"
  26
  27 CompareProjection::FourCorners::FourCorners(const WindowProjection &projection)
  28   :top_left(projection.ScreenToGeo(0, 0)),
  29    top_right(projection.ScreenToGeo(projection.GetScreenWidth(), 0)),
  30    bottom_left(projection.ScreenToGeo(0, projection.GetScreenHeight())),
  31    bottom_right(projection.ScreenToGeo(projection.GetScreenWidth(),
  32                                        projection.GetScreenHeight())) {}
  33
  34 gcc_pure
  35 static fixed
  36 SimpleSquareDistance(const GeoPoint &a, const GeoPoint &b,
  37                      const fixed latitude_cos)
  38 {
  39   return SmallHypot((a.longitude - b.longitude).AsDelta().Native(),
  40                     (a.latitude - b.latitude).AsDelta().Native() * latitude_cos);
  41 }
  42
  43 CompareProjection::CompareProjection(const WindowProjection &projection)
  44   :corners(projection),
  45    latitude_cos(corners.top_left.latitude.fastcosine()),
  46    max_delta(SimpleSquareDistance(corners.top_left, corners.top_right,
  47                                   latitude_cos) /
  48              (projection.GetScreenWidth() * projection.GetScreenWidth()))
  49 {
  50 }
  51
  52 bool
  53 CompareProjection::Compare(const CompareProjection &other) const
  54 {
  55   return positive(max_delta) &&
  56     SimpleSquareDistance(corners.top_left, other.corners.top_left,
  57                          latitude_cos) <= max_delta &&
  58     SimpleSquareDistance(corners.top_right, other.corners.top_right,
  59                          latitude_cos) <= max_delta &&
  60     SimpleSquareDistance(corners.bottom_left, other.corners.bottom_left,
  61                          latitude_cos) <= max_delta &&
  62     SimpleSquareDistance(corners.bottom_right, other.corners.bottom_right,
  63                          latitude_cos) <= max_delta;
  64 }
  65
  66 bool
  67 CompareProjection::CompareAndUpdate(const CompareProjection &other)
  68 {
  69   if (Compare(other))
  70     return true;
  71
  72   *this = other;
  73   return false;
  74 }
  75