Review fixes.

4 files changed, 87 insertions, 22 deletions

diff --git a/geometry/geometry_tests/robust_test.cpp b/geometry/geometry_tests/robust_test.cpp
index d20703361f..fc54df02ac 100644
--- a/geometry/geometry_tests/robust_test.cpp
+++ b/geometry/geometry_tests/robust_test.cpp
@@ -11,17 +11,17 @@ namespace
 {
 using P = m2::PointD;
 
-template <typename IterT>
-void CheckSelfIntersections(IterT beg, IterT end, bool res)
+template <typename TIt>
+void CheckSelfIntersections(TIt beg, TIt end, bool res)
 {
   TEST_EQUAL(CheckPolygonSelfIntersections(beg, end), res, ());
-  using ReverseIterT = reverse_iterator<IterT>;
-  TEST_EQUAL(CheckPolygonSelfIntersections(ReverseIterT(end), ReverseIterT(beg)), res, ());
+  using TRevIt = reverse_iterator<TIt>;
+  TEST_EQUAL(CheckPolygonSelfIntersections(TRevIt(end), TRevIt(beg)), res, ());
 }
 
-bool InsideSegment(P const & p, P const ps[])
+bool OnSegment(P const & p, P const ps[])
 {
-  return IsPointInsideSegment(p, ps[0], ps[1]);
+  return IsPointOnSegment(p, ps[0], ps[1]);
 }
 
 bool InsideTriangle(P const & p, P const ps[])
@@ -42,26 +42,48 @@ UNIT_TEST(Segment_Smoke)
   double constexpr eps = 1.0E-10;
   {
     P ps[] = {{0, 0}, {1, 0}};
-    TEST(InsideSegment(ps[0], ps), ());
-    TEST(InsideSegment(ps[1], ps), ());
-    TEST(InsideSegment(P(0.5, 0), ps), ());
+    TEST(OnSegment(ps[0], ps), ());
+    TEST(OnSegment(ps[1], ps), ());
+    TEST(OnSegment(P(0.5, 0), ps), ());
 
-    TEST(InsideSegment(P(eps, 0), ps), ());
-    TEST(InsideSegment(P(1.0 - eps, 0), ps), ());
+    TEST(OnSegment(P(eps, 0), ps), ());
+    TEST(OnSegment(P(1.0 - eps, 0), ps), ());
 
-    TEST(!InsideSegment(P(-eps, 0), ps), ());
-    TEST(!InsideSegment(P(1.0 + eps, 0), ps), ());
-    TEST(!InsideSegment(P(eps, eps), ps), ());
-    TEST(!InsideSegment(P(eps, -eps), ps), ());
+    TEST(!OnSegment(P(-eps, 0), ps), ());
+    TEST(!OnSegment(P(1.0 + eps, 0), ps), ());
+    TEST(!OnSegment(P(eps, eps), ps), ());
+    TEST(!OnSegment(P(eps, -eps), ps), ());
   }
 
   {
     P ps[] = {{10, 10}, {10, 10}};
-    TEST(InsideSegment(ps[0], ps), ());
-    TEST(InsideSegment(ps[1], ps), ());
-    TEST(!InsideSegment(P(10 - eps, 10), ps), ());
-    TEST(!InsideSegment(P(10 + eps, 10), ps), ());
-    TEST(!InsideSegment(P(0, 0), ps), ());
+    TEST(OnSegment(ps[0], ps), ());
+    TEST(OnSegment(ps[1], ps), ());
+    TEST(!OnSegment(P(10 - eps, 10), ps), ());
+    TEST(!OnSegment(P(10 + eps, 10), ps), ());
+    TEST(!OnSegment(P(0, 0), ps), ());
+  }
+
+  // Paranoid tests.
+  {
+    P ps[] = {{0, 0}, {1e100, 1e100}};
+    TEST(OnSegment(ps[0], ps), ());
+    TEST(OnSegment(ps[1], ps), ());
+    TEST(OnSegment(P(1e50, 1e50), ps), ());
+    TEST(!OnSegment(P(1e50, 1.00000000001e50), ps), ());
+
+    TEST(OnSegment(P(1e-100, 1e-100), ps), ());
+    TEST(!OnSegment(P(1e-100, 1e-100 + 1e-115), ps), ());
+  }
+
+  {
+    P ps[] = {{0, 0}, {2e100, 1e100}};
+    TEST(OnSegment(P(2.0 / 3.0, 1.0 / 3.0), ps), ());
+  }
+
+  {
+    P ps[] = {{0, 0}, {1e-15, 1e-15}};
+    TEST(!OnSegment(P(1e-16, 2.0 * 1e-16), ps), ());
   }
 }
 
diff --git a/geometry/segment2d.cpp b/geometry/segment2d.cpp
new file mode 100644
index 0000000000..bf7d05a12f
--- /dev/null
+++ b/geometry/segment2d.cpp
@@ -0,0 +1,35 @@
+#include "geometry/segment2d.hpp"
+
+#include "geometry/robust_orientation.hpp"
+
+#include "std/algorithm.hpp"
+
+namespace m2
+{
+bool IsPointOnSegment(m2::PointD const & pt, m2::PointD const & p1, m2::PointD const & p2)
+{
+  // The epsilon here is chosen quite arbitrarily, to pass paranoid
+  // tests and to match our real-data geometry precision. If you have
+  // better ideas how to check whether pt belongs to (p1, p2) segment
+  // more precisely or without kEps, feel free to submit a pull
+  // request.
+  double const kEps = 1e-100;
+
+  double const t = robust::OrientedS(p1, p2, pt);
+
+  if (fabs(t) > kEps)
+    return false;
+
+  double minX = p1.x;
+  double maxX = p2.x;
+  if (maxX < minX)
+    swap(maxX, minX);
+
+  double minY = p1.y;
+  double maxY = p2.y;
+  if (maxY < minY)
+    swap(maxY, minY);
+
+  return pt.x >= minX && pt.x <= maxX && pt.y >= minY && pt.y <= maxY;
+}
+}  // namespace m2
diff --git a/geometry/segment2d.hpp b/geometry/segment2d.hpp
new file mode 100644
index 0000000000..e5e64bb054
--- /dev/null
+++ b/geometry/segment2d.hpp
@@ -0,0 +1,8 @@
+#pragma once
+
+#include "geometry/point2d.hpp"
+
+namespace m2
+{
+bool IsPointOnSegment(m2::PointD const & pt, m2::PointD const & p1, m2::PointD const & p2);
+}  // namespace m2
diff --git a/geometry/triangle2d.cpp b/geometry/triangle2d.cpp
index cbecf3a7f4..1bd0f56f4c 100644
--- a/geometry/triangle2d.cpp
+++ b/geometry/triangle2d.cpp
@@ -18,8 +18,8 @@ bool IsPointInsideTriangle(m2::PointD const & pt, m2::PointD const & p1,
   // on (p1, p2), (p2, p3) or (p3, p1).
   if (s1 == 0.0 && s2 == 0.0 && s3 == 0.0)
   {
-    return IsPointInsideSegment(pt, p1, p2) || IsPointInsideSegment(pt, p2, p3) ||
-           IsPointInsideSegment(pt, p3, p1);
+    return IsPointOnSegment(pt, p1, p2) || IsPointOnSegment(pt, p2, p3) ||
+           IsPointOnSegment(pt, p3, p1);
   }
 
   return ((s1 >= 0.0 && s2 >= 0.0 && s3 >= 0.0) ||