clipper.core.h - fixed ambiguous 'round' (#824)

                 also fixed a compiler warning (#823)

CPP/Clipper2Lib/include/clipper2/clipper.core.h

@@ -1,6 +1,6 @@
 /*******************************************************************************
 * Author    :  Angus Johnson                                                   *
-* Date      :  24 March 2024                                                   *
+* Date      :  27 April 2024                                                   *
 * Website   :  http://www.angusj.com                                           *
 * Copyright :  Angus Johnson 2010-2024                                         *
 * Purpose   :  Core Clipper Library structures and functions                   *
@@ -93,6 +93,13 @@ namespace Clipper2Lib
 #endif
   }
 
+  // can we call std::round on T? (default false) (#824)
+  template <typename T, typename = void>
+  struct is_round_invocable : std::false_type {};
+
+  template <typename T>
+  struct is_round_invocable<T, std::void_t<decltype(std::round(std::declval<T>()))>> : std::true_type {};
+
 
   //By far the most widely used filling rules for polygons are EvenOdd
   //and NonZero, sometimes called Alternate and Winding respectively.
@@ -111,8 +118,8 @@ namespace Clipper2Lib
     template <typename T2>
     inline void Init(const T2 x_ = 0, const T2 y_ = 0, const int64_t z_ = 0)
     {
-      if constexpr (std::numeric_limits<T>::is_integer &&
-        !std::numeric_limits<T2>::is_integer)
+      if constexpr (std::is_integral_v<T> &&
+        is_round_invocable<T2>::value && !std::is_integral_v<T2>)
       {
         x = static_cast<T>(std::round(x_));
         y = static_cast<T>(std::round(y_));
@@ -165,8 +172,8 @@ namespace Clipper2Lib
     template <typename T2>
     inline void Init(const T2 x_ = 0, const T2 y_ = 0)
     {
-      if constexpr (std::numeric_limits<T>::is_integer &&
-        !std::numeric_limits<T2>::is_integer)
+      if constexpr (std::is_integral_v<T> &&
+        is_round_invocable<T2>::value && !std::is_integral_v<T2>)
       {
         x = static_cast<T>(std::round(x_));
         y = static_cast<T>(std::round(y_));
@@ -184,7 +191,7 @@ namespace Clipper2Lib
     Point(const T2 x_, const T2 y_) { Init(x_, y_); }
 
     template <typename T2>
-    explicit Point<T>(const Point<T2>& p) { Init(p.x, p.y); }
+    explicit Point(const Point<T2>& p) { Init(p.x, p.y); }
 
     Point operator * (const double scale) const
     {
@@ -365,8 +372,8 @@ namespace Clipper2Lib
   {
     Rect<T1> result;
 
-    if constexpr (std::numeric_limits<T1>::is_integer &&
-      !std::numeric_limits<T2>::is_integer)
+    if constexpr (std::is_integral_v<T1> &&
+      is_round_invocable<T2>::value && !std::is_integral_v<T2>)
     {
       result.left = static_cast<T1>(std::round(rect.left * scale));
       result.top = static_cast<T1>(std::round(rect.top * scale));
@@ -518,7 +525,7 @@ namespace Clipper2Lib
   {
     Paths<T1> result;
 
-    if constexpr (std::numeric_limits<T1>::is_integer)
+    if constexpr (std::is_integral_v<T1>)
     {
       RectD r = GetBounds<double, T2>(paths);
       if ((r.left * scale_x) < min_coord ||
@@ -763,7 +770,7 @@ namespace Clipper2Lib
     T bb1maxx = CC_MAX(ln2a.x, ln2b.x);
     T bb1maxy = CC_MAX(ln2a.y, ln2b.y);
 
-    if constexpr (std::numeric_limits<T>::is_integer)
+    if constexpr (std::is_integral_v<T>)
     {
       int64_t originx = (CC_MIN(bb0maxx, bb1maxx) + CC_MAX(bb0minx, bb1minx)) >> 1;
       int64_t originy = (CC_MIN(bb0maxy, bb1maxy) + CC_MAX(bb0miny, bb1miny)) >> 1;
@@ -872,7 +879,7 @@ namespace Clipper2Lib
         static_cast<double>(offPt.y - seg1.y) * dy) /
       (Sqr(dx) + Sqr(dy));
     if (q < 0) q = 0; else if (q > 1) q = 1;
-    if constexpr (std::numeric_limits<T>::is_integer)
+    if constexpr (std::is_integral_v<T>)
       return Point<T>(
         seg1.x + static_cast<T>(nearbyint(q * dx)),
         seg1.y + static_cast<T>(nearbyint(q * dy)));