src/Projection/CompareProjection.hpp

   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 #ifndef XCSOAR_COMPARE_PROJECTION_HPP
  25 #define XCSOAR_COMPARE_PROJECTION_HPP
  26
  27 #include "Geo/GeoPoint.hpp"
  28 #include "Compiler.h"
  29
  30 class WindowProjection;
  31
  32 /**
  33  * This class remembers the screen bounds of an existing Projection
  34  * object, and compares it after a change.  It is used to check if
  35  * calculation results from the previous frame are still valid, or if
  36  * they should be discarded.
  37  */
  38 class CompareProjection {
  39   struct FourCorners {
  40     GeoPoint top_left, top_right, bottom_left, bottom_right;
  41
  42     FourCorners() {}
  43     FourCorners(const WindowProjection &projection);
  44   };
  45
  46   FourCorners corners;
  47
  48   fixed latitude_cos;
  49
  50   fixed max_delta;
  51
  52 public:
  53   /**
  54    * Creates a "cleared" object, so that comparisons are always false.
  55    */
  56   CompareProjection():max_delta(fixed(-1)) {}
  57
  58   explicit CompareProjection(const WindowProjection &projection);
  59
  60   /**
  61    * Clears the object, so that comparisons are always false.  Useful
  62    * to Invalidate a cache.
  63    */
  64   void Clear() {
  65     max_delta = fixed(-1);
  66   }
  67
  68   bool Compare(const CompareProjection &other) const;
  69
  70   /**
  71    * Is the new projection close enough to the saved one?
  72    */
  73   bool Compare(const WindowProjection &projection) const {
  74     return Compare(CompareProjection(projection));
  75   }
  76
  77   bool CompareAndUpdate(const CompareProjection &other);
  78
  79   /**
  80    * Is the new projection close enough to the saved one?  If not,
  81    * then the saved one is updated.
  82    */
  83   bool CompareAndUpdate(const WindowProjection &projection) {
  84     return CompareAndUpdate(CompareProjection(projection));
  85   }
  86 };
  87
  88 #endif