Add Region.Area

Commands.cs

@@ -117,6 +117,8 @@ namespace Boprs
 			{
 				contour.Draw();
 			}
+
+			acDoc.Editor.WriteMessage($"\nResult area: {bopr.Result.Area}");
 		}
 	}
 }

Contour.cs

@@ -23,19 +23,29 @@ namespace Boprs
 	{
 		public object Clone()
 		{
-			return new Contour() { Vertices = new List<Point2d>(Vertices) }; 
+			return new Contour(new List<Point2d>(Vertices)); 
 		}
 
 		/// <summary>
 		/// Vertices of the contour.
 		/// </summary>
-		public List<Point2d> Vertices { get; private set; }
+		private List<Point2d> Vertices { get; }
+
+		/// <summary>
+		/// Signed area of the contour.
+		/// </summary>
+		public double SignedArea { get; private set; }
 
         /// <summary>
         /// Are the vertices of the contour arranged in clockwise manner?
         /// </summary>
         /// <returns><c>true</c> if the contour is clockwise, <c>false</c> if counter-clockwise.</returns>
-		public bool IsClockwise()
+        public bool IsClockwise { get => SignedArea < 0; }
+
+		/// <summary>
+		/// Compute the signed area of the contour
+		/// </summary>
+		private void ComputeArea()
 		{
 			double areaSum = 0;
 
@@ -49,27 +59,31 @@ namespace Boprs
 				Point2d p1 = Vertices[(i + 1) % Vertices.Count];
 
 				// Compute the area under the trapezoid made by the current segment.
-				// Note that this is actually double the proper value, but we only care about its relation to 0.
+				// Note that this is actually double the proper value.
 				areaSum += (p1.X - p0.X) * (p1.Y + p0.Y);
 			}
 
-			return areaSum > 0;
+			// The above algorithm deems clockwise area to be positive,
+			// however we consider ccw contours to be positive, so we flip the value.
+            SignedArea = - areaSum / 2;
 		}
 
 		/// <summary>
 		/// Reverse the orientation of the contour.
 		/// </summary>
-		public void Reverse()
+		internal void Reverse()
 		{
 			Vertices.Reverse();
+			SignedArea *= -1;
 		}
 
 		/// <summary>
 		/// Constructor.
 		/// </summary>
-		public Contour()
+		public Contour(List<Point2d> vertices)
 		{
-			Vertices = new List<Point2d>();
+			Vertices = vertices;
+			ComputeArea();
 		}
 
 #if DEBUG
@@ -88,6 +102,7 @@ namespace Boprs
 				for(int i = 0; i < Vertices.Count; i++)
 				{
 					Line asLine = new Line(Vertices[i].To3d(), Vertices[(i + 1) % Vertices.Count].To3d());
+					asLine.Color = IsClockwise ? Color.FromRgb(255, 32, 32) : Color.FromRgb(32, 255, 32);
 					acBlkTblRec.AppendEntity(asLine);
 					acTrans.AddNewlyCreatedDBObject(asLine, true);
 				}

Region.cs

@@ -25,8 +25,16 @@ namespace Boprs
 		/// </summary>
 		private List<SweepEdge> Edges { get; set; }
 
+		/// <summary>
+		/// Contours making up the region.
+		/// </summary>
 		private List<Contour> Contours { get; set; }
 
+		/// <summary>
+		/// Area of the positive part of the region (holes subtracted).
+		/// </summary>
+		public double Area { get; private set; }
+
 		/// <summary>
 		/// Subdivide my edges, set their inOut tags and validate their non-colinearity.
 		/// </summary>
@@ -163,8 +171,6 @@ namespace Boprs
 				}
 
 				// Otherwise this is an edge on an indiscovered contour, create it.
-				Contour contour = new Contour();
-				contours.Add(contour);
 
 				// acVx should be guaranteed to be the lowest and leftest vertex of the new polygon.
 				// Thus it cannot be vertical.
@@ -178,8 +184,7 @@ namespace Boprs
 				int pos = i;
 				processed[i] = true;
 				Point2d target = acVx.Point;
-				contour.Vertices.Add(vertices[pos].Point);
-				acVx.Edge.ParentContour = contour;
+                List<Point2d> contourVertices = new List<Point2d>() { vertices[pos].Point };
 				while (!Utils.DoubleEquals(vertices[pos].OtherVertex().Point.GetDistanceTo(target), 0))
 				{
 					int otherPos = vertices.IndexOf(vertices[pos].OtherVertex());
@@ -188,13 +193,16 @@ namespace Boprs
 					processed[pos] = true;
 					processed[otherPos] = true;
 
-					vertices[pos].Edge.ParentContour = contour;
-					contour.Vertices.Add(vertices[pos].Point);
+                    contourVertices.Add(vertices[pos].Point);
 				}
 				processed[vertices.IndexOf(vertices[pos].OtherVertex())] = true;
 
+				// Instantiate the contour object from the found vertices.
+                Contour contour = new Contour(contourVertices);
+                contours.Add(contour);
+
                 // If the contour is a hole and winds ccw, or positive and winds cw, flip it.
-				if (shouldBeCW != contour.IsClockwise())
+                if (shouldBeCW != contour.IsClockwise)
 				{
 					contour.Reverse();
 				}
@@ -202,6 +210,21 @@ namespace Boprs
 			Contours = contours;
 		}
 
+        /// <summary>
+        /// Compute the area of the region.
+        /// </summary>
+        /// <remarks>
+        /// Requires contours to be computed.
+        /// </remarks>
+        private void ComputeArea()
+		{
+			Area = 0;
+			foreach(Contour contour in Contours)
+			{
+				Area += contour.SignedArea;
+			}
+		}
+
 		/// <summary>
 		/// Get a copy of the regions edges list.
 		/// </summary>
@@ -255,6 +278,7 @@ namespace Boprs
 
 			region.SetEdges(vertices);
 			region.ComputeContours();
+			region.ComputeArea();
 
 			return region;
 		}

SweepEdge.cs

@@ -137,11 +137,6 @@ namespace Boprs
 		/// </summary>
 		internal Region ParentRegion { get; set; }
 
-		/// <summary>
-		/// Contour I belong to.
-		/// </summary>
-		internal Contour ParentContour { get; set; }
-
 		/// <summary>
 		/// Is this edge vertical?
 		/// </summary>