Add std::hash specialization for VECTOR2I

libs/kimath/CMakeLists.txt

@@ -21,6 +21,7 @@ set( KIMATH_SRCS
     src/geometry/shape_segment.cpp
 
 
+    src/math/vector2.cpp
     src/math/util.cpp
 )
 

libs/kimath/include/math/vector2d.h

@@ -627,12 +627,29 @@ std::ostream& operator<<( std::ostream& aStream, const VECTOR2<T>& aVector )
     return aStream;
 }
 
-
 /* Default specializations */
 typedef VECTOR2<double>       VECTOR2D;
 typedef VECTOR2<int>          VECTOR2I;
 typedef VECTOR2<unsigned int> VECTOR2U;
 
+/* STL specializations */
+namespace std
+{
+    // Required to enable correct use in std::map/unordered_map
+    template <>
+    struct hash<VECTOR2I>
+    {
+        size_t operator()( const VECTOR2I& k ) const;
+    };
+
+    // Required to enable use of std::hash with maps
+    template <>
+    struct less<VECTOR2I>
+    {
+        bool operator()( const VECTOR2I& aA, const VECTOR2I& aB ) const;
+    };
+}
+
 /* Compatibility typedefs */
 // FIXME should be removed to avoid multiple typedefs for the same type
 typedef VECTOR2<double> DPOINT;

libs/kimath/src/math/vector2.cpp

@@ -0,0 +1,40 @@
+/*
+ * This program source code file is part of KiCad, a free EDA CAD application.
+ *
+ * Copyright (C) 2022 KiCad Developers, see AUTHORS.txt for contributors.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <math/vector2d.h>
+
+
+size_t std::hash<VECTOR2I>::operator()( const VECTOR2I& k ) const
+{
+    auto xhash = std::hash<int>()( k.x );
+
+    // 0x9e3779b9 is 2^33 / ( 1 + sqrt(5) )
+    // Adding this value ensures that consecutive bits of y will not be close to each other
+    // decreasing the likelihood of hash collision in similar values of x and y
+    return xhash ^ ( std::hash<int>()( k.y ) + 0x9e3779b9 + ( xhash << 6 ) + ( xhash >> 2 ) );
+}
+
+
+bool std::less<VECTOR2I>::operator()( const VECTOR2I& aA, const VECTOR2I& aB ) const
+{
+    if( aA.x == aB.x )
+        return aA.y < aB.y;
+
+    return aA.x < aB.x;
+}