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polygon.cpp

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00001 /* ScummVM - Graphic Adventure Engine
00002  *
00003  * ScummVM is the legal property of its developers, whose names
00004  * are too numerous to list here. Please refer to the COPYRIGHT
00005  * file distributed with this source distribution.
00006  *
00007  * This program is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU General Public License
00009  * as published by the Free Software Foundation; either version 2
00010  * of the License, or (at your option) any later version.
00011  *
00012  * This program is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU General Public License
00018  * along with this program; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
00020  *
00021  */
00022 
00023 #include "common/scummsys.h"
00024 
00025 #ifdef ENABLE_VKEYBD
00026 
00027 #include "backends/vkeybd/polygon.h"
00028 
00029 namespace Common {
00030 
00031 bool Polygon::contains(int16 x, int16 y) const {
00032     int yflag0;
00033     int yflag1;
00034     bool inside_flag = false;
00035     unsigned int pt;
00036 
00037     const Point *vtx0 = &_points[_points.size() - 1];
00038     const Point *vtx1 = &_points[0];
00039 
00040     yflag0 = (vtx0->y >= y);
00041     for (pt = 0; pt < _points.size(); pt++, vtx1++) {
00042         yflag1 = (vtx1->y >= y);
00043         if (yflag0 != yflag1) {
00044             if (((vtx1->y - y) * (vtx0->x - vtx1->x) >=
00045                     (vtx1->x - x) * (vtx0->y - vtx1->y)) == yflag1) {
00046                 inside_flag = !inside_flag;
00047             }
00048         }
00049         yflag0 = yflag1;
00050         vtx0 = vtx1;
00051     }
00052 
00053     return inside_flag;
00054 }
00055 
00056 } // End of namespace Common
00057 
00058 #endif // #ifdef ENABLE_VKEYBD


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