Improved PolyTree access.

Author: AngusJohnson

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

@@ -321,10 +321,21 @@ namespace Clipper2Lib {
 		Path64 polygon_;
 	public:
 		explicit PolyPath64(PolyPath64* parent = nullptr) : PolyPath(parent) {}
+
 		~PolyPath64() {
 			childs_.resize(0);
 		}
-		PolyPath64* operator [] (size_t index) const { return childs_[index].get(); } const
+
+		const PolyPath64* operator [] (size_t index) const
+		{ 
+			return childs_[index].get(); 
+		} 
+
+		const PolyPath64* Child(size_t index) const
+		{
+			return childs_[index].get();
+		}
+
 		PolyPath64List::const_iterator begin() const { return childs_.cbegin(); }
 		PolyPath64List::const_iterator end() const { return childs_.cend(); }
 
@@ -367,13 +378,21 @@ namespace Clipper2Lib {
 		{
 			inv_scale_ = parent ? parent->inv_scale_ : 1.0;
 		}
+
 		~PolyPathD() {
 			childs_.resize(0);
 		}
-		PolyPathD* operator [] (size_t index)
+
+		const PolyPathD* operator [] (size_t index) const
 		{ 
 			return childs_[index].get();
 		}
+
+		const PolyPathD* Child(size_t index) const
+		{
+			return childs_[index].get();
+		}
+
 		PolyPathDList::const_iterator begin() const { return childs_.cbegin(); }
 		PolyPathDList::const_iterator end() const { return childs_.cend(); }
 

CSharp/Clipper2Lib/Clipper.Engine.cs

@@ -3363,28 +3363,38 @@ public object Current
 
     };
 
-    public bool IsHole => GetIsHole();
+    public bool IsHole
+    {
+      get { return GetIsHole(); }
+    }
 
     public PolyPathBase(PolyPathBase? parent = null) { _parent = parent; }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public int Level()
+    private int GetLevel()
     {
       int result = 0;
       PolyPathBase? pp = _parent;
       while (pp != null) { ++result; pp = pp._parent; }
       return result;
     }
 
+    public int Level
+    {
+      get { return GetLevel(); }
+    }
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private bool GetIsHole()
     {
-      int lvl = Level();
+      int lvl = GetLevel();
       return lvl != 0 && (lvl & 1) == 0;
     }
 
-    public int Count => _childs.Count;
-
+    public int Count
+    {
+      get { return _childs.Count; }
+    }
     internal abstract PolyPathBase AddChild(Path64 p);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -3409,16 +3419,24 @@ internal override PolyPathBase AddChild(Path64 p)
       return newChild;
     }
 
-    [IndexerName("Child")]
     public PolyPath64 this[int index]
     {
-      get {
+      get
+      {
         if (index < 0 || index >= _childs.Count)
           throw new InvalidOperationException();
-        return (PolyPath64) _childs[index]; 
+        return (PolyPath64) _childs[index];
       }
     }
 
+    public PolyPath64 Child(int index)
+    {
+      if (index < 0 || index >= _childs.Count)
+        throw new InvalidOperationException();
+      return (PolyPath64) _childs[index];
+    }
+
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public double Area()
     {

Delphi/Clipper2Lib/Clipper.Engine.pas

@@ -311,6 +311,7 @@   TPolyPathBase = class
     FChildList  : TList;
     function    GetChildCnt: Integer;
     function    GetIsHole: Boolean;
+    function    GetLevel: Integer;
   protected
     function    GetChild(index: Integer): TPolyPathBase;
     function    AddChild(const path: TPath64): TPolyPathBase; virtual; abstract;
@@ -323,6 +324,7 @@   TPolyPathBase = class
     property    IsHole: Boolean read GetIsHole;
     property    Count: Integer read GetChildCnt;
     property    Child[index: Integer]: TPolyPathBase read GetChild; default;
+    property    Level: Integer read GetLevel;
   end;
 
   TPolyPath64 = class(TPolyPathBase)
@@ -1887,6 +1889,10 @@ procedure TClipperBase.CleanCollinear(outRec: POutRec);
   op2 := startOp;
   while true do
   begin
+    // trim if collinear AND one of
+    //   a duplicate point OR
+    //   not preserving collinear points OR
+    //   is a 180 degree 'spike'
     if (CrossProduct(op2.prev.pt, op2.pt, op2.next.pt) = 0) and
       (PointsEqual(op2.pt,op2.prev.pt) or
       PointsEqual(op2.pt,op2.next.pt) or
@@ -3870,21 +3876,28 @@ function  TPolyPathBase.GetChild(index: Integer): TPolyPathBase;
 end;
 //------------------------------------------------------------------------------
 
-function  TPolyPathBase.GetIsHole: Boolean;
+function TPolyPathBase.GetLevel: Integer;
 var
   pp: TPolyPathBase;
 begin
-  pp := FParent;
-  result := assigned(pp);
-  if not Result then Exit;
-  while assigned(pp) do
+  Result := 0;
+  pp := Parent;
+  while Assigned(pp) do
   begin
-    result := not result;
-    pp := pp.FParent;
+    inc(Result);
+    pp := pp.Parent;
   end;
 end;
 //------------------------------------------------------------------------------
 
+function  TPolyPathBase.GetIsHole: Boolean;
+begin
+  if not Assigned(Parent) then
+    Result := false else
+    Result := not Odd(GetLevel);
+end;
+//------------------------------------------------------------------------------
+
 function  TPolyPathBase.GetChildCnt: Integer;
 begin
   Result := FChildList.Count;