From 47d3f96b20c963988f56849d6e3e577545a88800 Mon Sep 17 00:00:00 2001
From: borovec zdenek <zdenek.borovec@dek-cz.com>
Date: Wed, 4 Sep 2024 13:59:00 +0200
Subject: [PATCH] Contours orientate themselves properly.

---
 Boprs.csproj |  3 +++
 Contour.cs   | 26 ++++++++++++++++++++++----
 Region.cs    | 18 ++++++++++++++----
 SweepEdge.cs |  5 +++++
 SweepLine.cs | 21 +++++++++++++++++++++
 5 files changed, 65 insertions(+), 8 deletions(-)

diff --git a/Boprs.csproj b/Boprs.csproj
index 34f83ee..92732e9 100644
--- a/Boprs.csproj
+++ b/Boprs.csproj
@@ -41,6 +41,9 @@
     <Reference Include="acmgd">
       <HintPath>..\..\..\..\..\Program Files\Autodesk\AutoCAD 2024\acmgd.dll</HintPath>
     </Reference>
+    <Reference Include="BricscadExtensions">
+      <HintPath>References\BricscadExtensions.dll</HintPath>
+    </Reference>
     <Reference Include="BrxMgd">
       <HintPath>..\..\..\..\..\Program Files\Bricsys\BricsCAD V24 en_US\BrxMgd.dll</HintPath>
     </Reference>
diff --git a/Contour.cs b/Contour.cs
index 50f9432..8d781e4 100644
--- a/Contour.cs
+++ b/Contour.cs
@@ -13,6 +13,7 @@ using AcAp = Bricscad.ApplicationServices;
 #endif
 using System;
 using System.Collections.Generic;
+using BricscadExtensions;
 
 namespace Boprs
 {
@@ -22,9 +23,9 @@ namespace Boprs
 	public class Contour
 	{
 		/// <summary>
-		/// Parent of this contour, null if external.
+		/// Depth of the contour within the region.
 		/// </summary>
-		public Contour Parent { get; internal set; }
+		internal int ContourDepth { get; set; }
 
 		/// <summary>
 		/// Vertices of the contour.
@@ -37,7 +38,23 @@ namespace Boprs
 		/// <returns><c>true</c> if the contour is clockwise, <c>false</c> if counter-clockwise.</returns>
 		public bool IsClockwise()
 		{
-			throw new NotImplementedException();
+			double areaSum = 0;
+
+			// Go through all the vertices.
+			for (int i = 0; i < Vertices.Count; i++)
+			{
+				// Get current vertex
+				Point2d p0 = Vertices[i];
+
+				// Get the next vertex
+				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.
+				areaSum += (p1.X - p0.X) * (p1.Y + p0.Y);
+			}
+
+			return areaSum > 0;
 		}
 
 		/// <summary>
@@ -45,7 +62,7 @@ namespace Boprs
 		/// </summary>
 		public void Reverse()
 		{
-			throw new NotImplementedException();
+			Vertices.Reverse();
 		}
 
 		/// <summary>
@@ -53,6 +70,7 @@ namespace Boprs
 		/// </summary>
 		public Contour()
 		{
+			ContourDepth = 0;
 			Vertices = new List<Point2d>();
 		}
 
diff --git a/Region.cs b/Region.cs
index a4ed208..09b643c 100644
--- a/Region.cs
+++ b/Region.cs
@@ -174,26 +174,36 @@ namespace Boprs
 				{
 					continue;
 				}
-				processed[i] = true;
 
-				// We should be guaranteed to always hit left endpoint leading us on a counter clockwise path.
 				Contour contour = new Contour();
 				contours.Add(contour);
 
+				SweepEdge prev = sweepLine.PrevEdge(acVx.Edge);
+				bool shouldBeCW = prev == null ? false : prev.TransitionInside;
+
 				Point2d target = acVx.Point;
 
 				int pos = i;
+				processed[i] = true;
+				contour.Vertices.Add(vertices[pos].Point);
+				acVx.Edge.ParentContour = contour;
 				while (!Utils.DoubleEquals(vertices[pos].OtherVertex().Point.GetDistanceTo(target), 0))
 				{
 					int otherPos = vertices.IndexOf(vertices[pos].OtherVertex());
 					pos = NextPos(otherPos, vertices, processed);
 
-					contour.Vertices.Add(vertices[pos].Point);
 					processed[pos] = true;
-
 					processed[otherPos] = true;
+
+					vertices[pos].Edge.ParentContour = contour;
+					contour.Vertices.Add(vertices[pos].Point);
 				}
 				processed[vertices.IndexOf(vertices[pos].OtherVertex())] = true;
+				
+				if (shouldBeCW != contour.IsClockwise())
+				{
+					contour.Reverse();
+				}
 			}
 			Contours = contours;
 		}
diff --git a/SweepEdge.cs b/SweepEdge.cs
index cbd329d..6334ed8 100644
--- a/SweepEdge.cs
+++ b/SweepEdge.cs
@@ -137,6 +137,11 @@ 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>
diff --git a/SweepLine.cs b/SweepLine.cs
index 1435e4c..6d1279b 100644
--- a/SweepLine.cs
+++ b/SweepLine.cs
@@ -77,6 +77,27 @@ namespace Boprs
 			IntersectingEdges.Remove(edge);
 		}
 
+		/// <summary>
+		/// Get all edges on the sweepline below a given edge.
+		/// </summary>
+		/// <param name="curr">Current edge.</param>
+		/// <returns>From lowest to highest.</returns>
+		internal List<SweepEdge> AllBefore(SweepEdge curr)
+		{
+			List<SweepEdge> foundEdges = new List<SweepEdge>();
+
+			// Get the index of the current edge
+			int currIdx = IntersectingEdges.IndexOf(curr);
+
+			// Add all the previous edges to the list
+			for(int i = 0; i < currIdx; i++)
+			{
+				foundEdges.Add(IntersectingEdges[i]);
+			}
+
+			return foundEdges;
+		}
+
 		/// <summary>
 		/// Returns the edge below curr, or null if curr is the lowest.
 		/// </summary>