Modified edge transformation to maintain the orientation paradigm

When the transformation is mirroring, edges now swap their
points to maintain the right-is-inside paradigm.

src/db/db/dbEdge.h

@@ -336,7 +336,14 @@ public:
   template <class Tr>
   edge<C> &transform (const Tr &t)
   {
-    *this = edge<C> (t * m_p1, t * m_p2);
+    if (t.is_mirror ()) {
+      //  NOTE: in case of mirroring transformations we swap p1 and p2. The reasoning is that
+      //  this way we maintain the orientation semantics: "right" of the edge is "inside" of
+      //  an area.
+      *this = edge<C> (t * m_p2, t * m_p1);
+    } else {
+      *this = edge<C> (t * m_p1, t * m_p2);
+    }
     return *this;
   }
 
@@ -353,7 +360,14 @@ public:
   template <class Tr>
   edge<typename Tr::target_coord_type> transformed (const Tr &t) const
   {
-    return edge<typename Tr::target_coord_type> (t * m_p1, t * m_p2);
+    if (t.is_mirror ()) {
+      //  NOTE: in case of mirroring transformations we swap p1 and p2. The reasoning is that
+      //  this way we maintain the orientation semantics: "right" of the edge is "inside" of
+      //  an area.
+      return edge<typename Tr::target_coord_type> (t * m_p2, t * m_p1);
+    } else {
+      return edge<typename Tr::target_coord_type> (t * m_p1, t * m_p2);
+    }
   }
 
   /**
@@ -914,7 +928,7 @@ public:
   }
 
   /**
-   *  @brief Swap the points of the edge
+   *  @brief Swaps the points of the edge
    */
   edge<C> &swap_points () 
   {

src/db/unit_tests/dbEdge.cc

@@ -29,6 +29,7 @@
 TEST(1) 
 {
   db::Edge e (0, 0, 100, 200);
+  db::Edge ee;
   db::Edge empty;
 
   EXPECT_EQ (empty.is_degenerate (), true);
@@ -53,6 +54,12 @@ TEST(1)
   EXPECT_EQ (e.to_string (), "(0,0;100,200)");
   EXPECT_EQ (e.swapped_points ().to_string (), "(100,200;0,0)");
   EXPECT_EQ (e.to_string (), "(0,0;100,200)");
+  EXPECT_EQ (e.transformed (db::Trans (1)).to_string (), "(0,0;-200,100)");
+  EXPECT_EQ (e.transformed (db::Trans (5)).to_string (), "(200,100;0,0)");   //  mirroring transformations swap points
+  ee = e;
+  ee.transform (db::Trans (5));
+  EXPECT_EQ (ee.to_string (), "(200,100;0,0)");
+  EXPECT_EQ (e.swapped_points ().to_string (), "(100,200;0,0)");
   e.swap_points ();
   EXPECT_EQ (e.to_string (), "(100,200;0,0)");
 
@@ -66,7 +73,6 @@ TEST(1)
   EXPECT_EQ (e.shifted (2).to_string (), "(0,4;10,12)");
   EXPECT_EQ (e.shifted (1).to_string (), "(0,3;10,11)");
 
-  db::Edge ee;
   ee = e;
   ee.shift (2);
   EXPECT_EQ (ee.to_string (), "(0,4;10,12)");