Fixed an integer overflow error in ClipperOffset (#867)

Author: AngusJohnson

CSharp/Clipper2Lib/Clipper.Offset.cs

@@ -1,6 +1,6 @@
 /*******************************************************************************
 * Author    :  Angus Johnson                                                   *
-* Date      :  17 April 2024                                                   *
+* Date      :  13 July 2024                                                    *
 * Website   :  http://www.angusj.com                                           *
 * Copyright :  Angus Johnson 2010-2024                                         *
 * Purpose   :  Path Offset (Inflate/Shrink)                                    *
@@ -513,8 +513,8 @@ private void BuildNormals(Path64 path)
     {
       int cnt = path.Count;
       _normals.Clear();
+      if (cnt == 0) return;
       _normals.EnsureCapacity(cnt);
-
       for (int i = 0; i < cnt - 1; i++)
         _normals.Add(GetUnitNormal(path[i], path[i + 1]));
       _normals.Add(GetUnitNormal(path[cnt - 1], path[0]));

Delphi/Clipper2Lib/Clipper.Offset.pas

@@ -2,7 +2,7 @@
 
 (*******************************************************************************
 * Author    :  Angus Johnson                                                   *
-* Date      :  17 April 2024                                                   *
+* Date      :  6 July 2024                                                     *
 * Website   :  http://www.angusj.com                                           *
 * Copyright :  Angus Johnson 2010-2024                                         *
 * Purpose   :  Path Offset (Inflate/Shrink)                                    *
@@ -236,9 +236,7 @@ function UnsafeGet(List: TList; Index: Integer): Pointer;
 constructor TGroup.Create(const pathsIn: TPaths64; jt: TJoinType; et: TEndType);
 var
   i, len: integer;
-  a: double;
   isJoined: boolean;
-  pb: PBoolean;
 begin
   Self.joinType := jt;
   Self.endType := et;
@@ -345,7 +343,6 @@ procedure TClipperOffset.DoGroupOffset(group: TGroup);
   i,j, len, steps: Integer;
   r, stepsPer360, arcTol: Double;
   absDelta: double;
-  isShrinking: Boolean;
   rec: TRect64;
   pt0: TPoint64;
 begin
@@ -450,6 +447,7 @@ procedure TClipperOffset.BuildNormals;
 begin
   len := Length(fInPath);
   SetLength(fNorms, len);
+  if len = 0 then Exit;
   for i := 0 to len-2 do
     fNorms[i] := GetUnitNormal(fInPath[i], fInPath[i+1]);
   fNorms[len -1] := GetUnitNormal(fInPath[len -1], fInPath[0]);