
#region ================== Copyright (c) 2007 Pascal vd Heiden

/*
 * Copyright (c) 2007 Pascal vd Heiden, www.codeimp.com
 * This program is released under GNU General Public License
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 */

#endregion

#region ================== Namespaces

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;
using CodeImp.DoomBuilder.Config;
using CodeImp.DoomBuilder.Data;
using CodeImp.DoomBuilder.Map;
using CodeImp.DoomBuilder.Rendering;
using CodeImp.DoomBuilder.Types;
using CodeImp.DoomBuilder.VisualModes;

#endregion

namespace CodeImp.DoomBuilder.Geometry
{
	/// <summary>
	/// Tools to work with geometry.
	/// </summary>
	public static class Tools
	{
		#region ================== Structures

		private struct SidedefSettings
		{
			public string newtexhigh;
			public string newtexmid;
			public string newtexlow;
		}

		public struct SidedefFillJob
		{
			public Sidedef sidedef;

			// Moving forward along the sidedef?
			public bool forward;
		}

		#endregion
		
		#region ================== Constants

		//mxd
		private const float MINIMUM_INTERSECTION_DISTANCE = 0.25f;
		
		#endregion

		#region ================== Polygons and Triangles

		// Point inside the polygon?
		// See: http://local.wasp.uwa.edu.au/~pbourke/geometry/insidepoly/
		public static bool PointInPolygon(ICollection<Vector2D> polygon, Vector2D point)
		{
			Vector2D v1 = General.GetByIndex(polygon, polygon.Count - 1);
			uint c = 0;

			// Go for all vertices
			foreach(Vector2D v2 in polygon)
			{
				// Determine min/max values
				double miny = Math.Min(v1.y, v2.y);
				double maxy = Math.Max(v1.y, v2.y);
				double maxx = Math.Max(v1.x, v2.x);

				// Check for intersection
				if((point.y > miny) && (point.y <= maxy))
				{
					if(point.x <= maxx)
					{
						if(v1.y != v2.y)
						{
							double xint = (point.y - v1.y) * (v2.x - v1.x) / (v2.y - v1.y) + v1.x;
							if((v1.x == v2.x) || (point.x <= xint)) c++;
						}
					}
				}

				// Move to next
				v1 = v2;
			}

			// Inside this polygon?
			return (c & 0x00000001UL) != 0;
		}
		
		#endregion
		
		#region ================== Pathfinding

		/// <summary>
		/// This finds a potential sector at the given coordinates,
		/// or returns null when a sector is not possible there.
		/// </summary>
		public static List<LinedefSide> FindPotentialSectorAt(Vector2D pos)
		{
			// Find the nearest line and determine side, then use the other method to create the sector
			Linedef l = General.Map.Map.NearestLinedef(pos);
			return FindPotentialSectorAt(l, (l.SideOfLine(pos) <= 0));
		}

		/// <summary>
		/// This finds a potential sector starting at the given line and side,
		/// or returns null when sector is not possible.
		/// </summary>
		public static List<LinedefSide> FindPotentialSectorAt(Linedef line, bool front)
		{
			List<LinedefSide> alllines = new List<LinedefSide>();
			
			// Find the outer lines
			EarClipPolygon p = FindOuterLines(line, front, alllines);
			if(p != null)
			{
				// Find the inner lines
				FindInnerLines(p, alllines);
				return alllines;
			}

			return null;
		}

		// This finds the inner lines of the sector and adds them to the sector polygon
		private static void FindInnerLines(EarClipPolygon p, List<LinedefSide> alllines)
		{
			bool findmore;
			double foundangle = 0f;
			RectangleF bbox = p.CreateBBox();
			
			do
			{
				findmore = false;

				// Go for all vertices to find the right-most vertex inside the polygon
				Vertex foundv = null;
				foreach(Vertex v in General.Map.Map.Vertices)
				{
					// Inside the polygon bounding box?
					if(v.Position.x < bbox.Left || v.Position.x > bbox.Right || v.Position.y < bbox.Top || v.Position.y > bbox.Bottom)
						continue;

					// More to the right?
					if((foundv == null) || (v.Position.x >= foundv.Position.x)) 
					{
						// Vertex is inside the polygon?
						if(p.Intersect(v.Position)) 
						{
							// Vertex has lines attached?
							if(v.Linedefs.Count > 0)
							{
								// Go for all lines to see if the vertex is not of the polygon itsself
								bool vvalid = true;
								foreach(LinedefSide ls in alllines) 
								{
									if((ls.Line.Start == v) || (ls.Line.End == v)) 
									{
										vvalid = false;
										break;
									}
								}

								// Valid vertex?
								if(vvalid) foundv = v;
							}
						}
					}
				}

				// Found a vertex inside the polygon?
				if(foundv != null)
				{
					// Find the attached linedef with the smallest angle to the right
					const double targetangle = Angle2D.PIHALF;
					Linedef foundline = null;
					foreach(Linedef l in foundv.Linedefs)
					{
						// We need an angle unrelated to line direction, so correct for that
						double lineangle = l.Angle;
						if(l.End == foundv) lineangle += Angle2D.PI;

						// Better result?
						double deltaangle = Angle2D.Difference(targetangle, lineangle);
						if((foundline == null) || (deltaangle < foundangle))
						{
							foundline = l;
							foundangle = deltaangle;
						}
					}

					// We already know that each linedef will go from this vertex
					// to the left, because this is the right-most vertex in this area.
					// If the line would go to the right, that means the other vertex of
					// that line must lie outside this area and the mapper made an error.
					// Should I check for this error and fail to create a sector in
					// that case or ignore it and create a malformed sector (possibly
					// breaking another sector also)?

					// Find the side at which to start pathfinding
					Vector2D testpos = new Vector2D(100.0f, 0.0f);
					bool foundlinefront = (foundline.SideOfLine(foundv.Position + testpos) < 0.0f);

					// Find inner path
					List<LinedefSide> innerlines = FindClosestPath(foundline, foundlinefront, true);
					if(innerlines != null)
					{
						// Make polygon
						LinedefTracePath tracepath = new LinedefTracePath(innerlines);
						EarClipPolygon innerpoly = tracepath.MakePolygon(true);

						//mxd. Check bbox first...
						Vector2D foundsidepoint = foundline.GetSidePoint(foundlinefront);
						RectangleF innerbbox = innerpoly.CreateBBox();
						bool outsidebbox = (foundsidepoint.x < innerbbox.Left || foundsidepoint.x > innerbbox.Right || foundsidepoint.y < innerbbox.Top || foundsidepoint.y > innerbbox.Bottom);

						// Check if the front of the line is outside the polygon
						if(outsidebbox || !innerpoly.Intersect(foundsidepoint))
						{
							// Valid hole found!
							alllines.AddRange(innerlines);
							p.InsertChild(innerpoly);
							findmore = true;
						}
					}
				}
			}
			// Continue until no more holes found
			while(findmore);
		}

		// This finds the outer lines of the sector as a polygon
		// Returns null when no valid outer polygon can be found
		private static EarClipPolygon FindOuterLines(Linedef line, bool front, List<LinedefSide> alllines)
		{
			Linedef scanline = line;
			bool scanfront = front;
			Vector2D sidepoint = line.GetSidePoint(front); //mxd

			do
			{
				// Find closest path
				List<LinedefSide> pathlines = FindClosestPath(scanline, scanfront, true);
				if(pathlines != null)
				{
					// Make polygon
					LinedefTracePath tracepath = new LinedefTracePath(pathlines);
					EarClipPolygon poly = tracepath.MakePolygon(true);

					//mxd. Check bbox first...
					RectangleF bbox = poly.CreateBBox();
					bool outsidebbox = (sidepoint.x < bbox.Left || sidepoint.x > bbox.Right || sidepoint.y < bbox.Top || sidepoint.y > bbox.Bottom);

					// Check if the front of the line is inside the polygon
					if(!outsidebbox && poly.Intersect(sidepoint))
					{
						// Outer lines found!
						alllines.AddRange(pathlines);
						return poly;
					}
					else
					{
						// Inner lines found. This is not what we need, we want the outer lines.
						// Find the right-most vertex to start a scan from there towards the outer lines.
						Vertex foundv = null;
						foreach(LinedefSide ls in pathlines)
						{
							if((foundv == null) || (ls.Line.Start.Position.x > foundv.Position.x))
								foundv = ls.Line.Start;
							
							if((foundv == null) || (ls.Line.End.Position.x > foundv.Position.x))
								foundv = ls.Line.End;
						}

						// If foundv is null then something is horribly wrong with the
						// path we received from FindClosestPath!
						if(foundv == null) throw new Exception("FAIL!");
						
						// From the right-most vertex trace outward to the right to find the next closest linedef,
						// this is based on the idea that all sectors are closed.

						//mxd. Intersection test is bounded, so extend end position x to the right map boundary
						Line2D testline = new Line2D(foundv.Position, new Vector2D(General.Map.Config.RightBoundary, foundv.Position.y));
						scanline = null;
						double foundu = double.MaxValue;

						double px = foundv.Position.x; //mxd
						double py = foundv.Position.y; //mxd
						double scanlinefoundvdistance = double.MaxValue;

						foreach(Linedef ld in General.Map.Map.Linedefs)
						{
							// Line to the right of start point?
							if((ld.Start.Position.x > px) || (ld.End.Position.x > px)) 
							{
								// Line intersecting the y axis?
								if((ld.Start.Position.y >= py && ld.End.Position.y <= py) 
									|| (ld.Start.Position.y <= py && ld.End.Position.y >= py)) //mxd
								{
									// Check if this linedef intersects our test line at a closer range
									double thisu;
									ld.Line.GetIntersection(testline, out thisu);
									if(!double.IsNaN(thisu) && (thisu > 0.00001f))
									{
										if(thisu < foundu)
										{
											scanline = ld;
											foundu = thisu;
											scanlinefoundvdistance = scanline.DistanceTo(foundv.Position, true);
										}
										//mxd. Special cases: when foundv.y matches ld's start or end y, 
										// prefer the line, which is clser to being parallel to the x axis
										else if(scanline != null && Math.Round(thisu, 4) == Math.Round(foundu, 4))
										{
											double ldanglerel, scanlineanglerel;
											if(GetRelativeAngle(ld, foundv.Position, out ldanglerel) 
												&& GetRelativeAngle(scanline, foundv.Position, out scanlineanglerel)
												&& (ldanglerel < scanlineanglerel))
											{
												// biwa. This fixes a problem with breaking geometry. It's unknown if this breaks the original fix
												// See https://github.com/jewalky/UltimateDoomBuilder/issues/556 for an explanation
												if (ld.DistanceTo(foundv.Position, true) < scanlinefoundvdistance)
												{
													scanline = ld; // foundu already matches
													scanlinefoundvdistance = scanline.DistanceTo(foundv.Position, true);
												}
											}
										}
									}
								}
							}
						}

						// Did we meet another line?
						if(scanline != null)
						{
							// Determine on which side we should start the next pathfind
							scanfront = (scanline.SideOfLine(foundv.Position) < 0.0);
						}
						else
						{
							// Appearently we reached the end of the map, no sector possible here
							return null;
						}
					}
				}
				else
				{
					// Can't find a path
					return null;
				}
			}
			while(true);
		}

		//mxd. Gets angle between pos and l when pos.y matches l.Start.Position.y or l.End.Position.y
		private static bool GetRelativeAngle(Linedef l, Vector2D pos, out double result)
		{
			if(l.Start.Position.y == pos.y)
			{
				result = Angle2D.GetAngle(pos, l.Start.Position, l.End.Position);
				return true;
			}

			if(l.End.Position.y == pos.y)
			{
				result = Angle2D.GetAngle(pos, l.End.Position, l.Start.Position);
				return true;
			}

			// We just don't know...
			result = float.MaxValue;
			return false;
		}

		/// <summary>
		/// This finds the closest path from the beginning of a line to the end of the line.
		/// When turnatends is true, the algorithm will continue at the other side of the
		/// line when a dead end has been reached. Returns null when no path could be found.
		/// </summary>
		public static List<LinedefSide> FindClosestPath(Linedef startline, bool startfront, bool turnatends)
		{
			return FindClosestPath(startline, startfront, startline, startfront, turnatends);
		}
		
		/// <summary>
		/// This finds the closest path from the beginning of a line to the end of the line.
		/// When turnatends is true, the algorithm will continue at the other side of the
		/// line when a dead end has been reached. Returns null when no path could be found.
		/// </summary>
		public static List<LinedefSide> FindClosestPath(Linedef startline, bool startfront, Linedef endline, bool endfront, bool turnatends)
		{
			List<LinedefSide> path = new List<LinedefSide>();
			Dictionary<Linedef, int> tracecount = new Dictionary<Linedef, int>();
			Linedef nextline = startline;
			bool nextfront = startfront;

			do
			{
				// Add line to path
				path.Add(new LinedefSide(nextline, nextfront));

				// Determine next vertex to use
				Vertex v = nextfront ? nextline.End : nextline.Start;

				// Get list of linedefs and sort by angle
				List<Linedef> lines = new List<Linedef>(v.Linedefs);
				LinedefAngleSorter sorter = new LinedefAngleSorter(nextline, nextfront, v);
				lines.Sort(sorter);

				// Source line is the only one?
				if(lines.Count == 1)
				{
					// Are we allowed to trace along this line again?
					if(turnatends && (!tracecount.ContainsKey(nextline) || (tracecount[nextline] < 3)))
					{
						// Turn around and go back along the other side of the line
						nextfront = !nextfront;
					}
					else
					{
						// No more lines, trace ends here
						path = null;
					}
				}
				else
				{
					// Trace along the next line
					Linedef prevline = nextline;
					nextline = (lines[0] == nextline ? lines[1] : lines[0]);

					//mxd. Try to pick a line with lower tracecount, otherwise we will just walk the same path trise
					int curcount = (!tracecount.ContainsKey(nextline) ? 0 : tracecount[nextline]);

					//mxd. Don't pick a different line for start and end lines, otherwise the path can go away from it instead of closing the path
					//mxd. Also don't pick a different line for marked lines (these are newly drawn lines, and we don't want to skip them)
					if(curcount > 0 && !nextline.Marked && nextline != startline && nextline != endline)
					{
						foreach(Linedef l in lines)
						{
							if(l != nextline && l != prevline && (!tracecount.ContainsKey(l) || tracecount[l] < curcount))
							{
								nextline = l;
								break;
							}
						}
					}

					// Are we allowed to trace this line again?
					if(!tracecount.ContainsKey(nextline) || (tracecount[nextline] < 3))
					{
						// Check if front side changes
						if(prevline.Start == nextline.Start || prevline.End == nextline.End)
							nextfront = !nextfront;
					}
					else
					{
						// No more lines, trace ends here
						path = null;
					}
				}

				//mxd. Increase trace count
				if(!tracecount.ContainsKey(nextline)) tracecount.Add(nextline, 1); else tracecount[nextline]++;
			}
			// Continue as long as we have not reached the start yet
			// or we have no next line to trace
			while((path != null) && ((nextline != endline) || (nextfront != endfront)));

			// If start and front are not the same, add the end to the list also
			if((path != null) && ((startline != endline) || (startfront != endfront)))
				path.Add(new LinedefSide(endline, endfront));
			
			// Return path (null when trace failed)
			return path;
		}

		#endregion
		
		#region ================== Sector Making

		// This makes the sector from the given lines and sides
		// If nearbylines is not null, then this method will find the default
		// properties from the nearest line in this collection when the
		// default properties can't be found in the alllines collection.
		// Return null when no new sector could be made.
		public static Sector MakeSector(List<LinedefSide> alllines, List<Linedef> nearbylines, bool useOverrides)
		{
			Sector sourcesector = null;
			SidedefSettings sourceside = new SidedefSettings();
			bool foundsidedefaults = false;

			if(General.Map.Map.Sectors.Count >= General.Map.FormatInterface.MaxSectors)
				return null;

			Sector newsector = General.Map.Map.CreateSector();
			if(newsector == null) return null;
			
			// Check if any of the sides already has a sidedef
			// Then we use information from that sidedef to make the others
			foreach(LinedefSide ls in alllines)
			{
				if(ls.Front)
				{
					if(ls.Line.Front != null)
					{
						// Copy sidedef information if not already found
						if(sourcesector == null) sourcesector = ls.Line.Front.Sector;
						TakeSidedefSettings(ref sourceside, ls.Line.Front);
						foundsidedefaults = true;
						break;
					}
				}
				else
				{
					if(ls.Line.Back != null)
					{
						// Copy sidedef information if not already found
						if(sourcesector == null) sourcesector = ls.Line.Back.Sector;
						TakeSidedefSettings(ref sourceside, ls.Line.Back);
						foundsidedefaults = true;
						break;
					}
				}
			}
			
			// Now do the same for the other sides
			// Note how information is only copied when not already found
			// so this won't override information from the sides searched above
			foreach(LinedefSide ls in alllines)
			{
				if(ls.Front)
				{
					if(ls.Line.Back != null)
					{
						// Copy sidedef information if not already found
						if(sourcesector == null) sourcesector = ls.Line.Back.Sector;
						TakeSidedefSettings(ref sourceside, ls.Line.Back);
						foundsidedefaults = true;
						break;
					}
				}
				else
				{
					if(ls.Line.Front != null)
					{
						// Copy sidedef information if not already found
						if(sourcesector == null) sourcesector = ls.Line.Front.Sector;
						TakeSidedefSettings(ref sourceside, ls.Line.Front);
						foundsidedefaults = true;
						break;
					}
				}
			}
			
			// Use default settings from the nearest linedef, if settings have not been found yet
			Sector nearestsector = null; //mxd
			if( (nearbylines != null) && (alllines.Count > 0) && (!foundsidedefaults || (sourcesector == null)) )
			{
				Vector2D testpoint = alllines[0].Line.GetSidePoint(alllines[0].Front);
				Linedef nearest = MapSet.NearestLinedef(nearbylines, testpoint);
				if(nearest != null)
				{
					double side = nearest.SideOfLine(testpoint);
					Sidedef defaultside = (side < 0.0f ? nearest.Front : nearest.Back);

					if(defaultside != null)
					{
						if(sourcesector == null) sourcesector = defaultside.Sector;
						TakeSidedefSettings(ref sourceside, defaultside);
					}
					else
					{
						//mxd. Any side is better than no side (but we'll want only basic settings from that)...
						defaultside = (side < 0.0f ? nearest.Back : nearest.Front);
						if(defaultside != null)
						{
							TakeSidedefSettings(ref sourceside, defaultside);
							nearestsector = defaultside.Sector;
						}
					}
				}
			}
			
			// Use defaults where no settings could be found
			TakeSidedefDefaults(ref sourceside);
			
			// Found a source sector?
			if(sourcesector != null)
			{
				// Copy properties from source to new sector
				sourcesector.CopyPropertiesTo(newsector);
			}
			else if(nearestsector != null)
			{
				//mxd. Apply basic properties from the nearest sector
				newsector.SetFloorTexture(nearestsector.FloorTexture);
				newsector.SetCeilTexture(nearestsector.CeilTexture);
				newsector.FloorHeight = nearestsector.FloorHeight;
				newsector.CeilHeight = nearestsector.CeilHeight;
				newsector.Brightness = nearestsector.Brightness;
			}
			else
			{
				// No source sector, apply default sector properties
				newsector.SetFloorTexture(General.Map.Options.DefaultFloorTexture);
				newsector.SetCeilTexture(General.Map.Options.DefaultCeilingTexture);
				newsector.FloorHeight = General.Settings.DefaultFloorHeight;
				newsector.CeilHeight = General.Settings.DefaultCeilingHeight;
				newsector.Brightness = General.Settings.DefaultBrightness;
			}

			//mxd. Apply overrides?
			if(useOverrides) 
			{
				if(General.Map.Options.OverrideCeilingTexture) newsector.SetCeilTexture(General.Map.Options.DefaultCeilingTexture);
				if(General.Map.Options.OverrideFloorTexture) newsector.SetFloorTexture(General.Map.Options.DefaultFloorTexture);
				if(General.Map.Options.OverrideCeilingHeight) newsector.CeilHeight = General.Map.Options.CustomCeilingHeight;
				if(General.Map.Options.OverrideFloorHeight) newsector.FloorHeight = General.Map.Options.CustomFloorHeight;
				if(General.Map.Options.OverrideBrightness) newsector.Brightness = General.Map.Options.CustomBrightness;
			}
			//mxd. Avoid invalid height
			else if(newsector.CeilHeight < newsector.FloorHeight)
			{
				 newsector.CeilHeight = newsector.FloorHeight;
			}

			// Go for all sides to make sidedefs
			foreach(LinedefSide ls in alllines)
			{
				// We may only remove a useless middle texture when
				// the line was previously singlesided
				bool wassinglesided = (ls.Line.Back == null) || (ls.Line.Front == null);
				
				if(ls.Front)
				{
					// Create sidedef is needed and ensure it points to the new sector
					if(ls.Line.Front == null) General.Map.Map.CreateSidedef(ls.Line, true, newsector);
					if(ls.Line.Front == null) return null;
					if(ls.Line.Front.Sector != newsector) ls.Line.Front.SetSector(newsector);
					ApplyDefaultsToSidedef(ls.Line.Front, sourceside);
				}
				else
				{
					// Create sidedef is needed and ensure it points to the new sector
					if(ls.Line.Back == null) General.Map.Map.CreateSidedef(ls.Line, false, newsector);
					if(ls.Line.Back == null) return null;
					if(ls.Line.Back.Sector != newsector) ls.Line.Back.SetSector(newsector);
					ApplyDefaultsToSidedef(ls.Line.Back, sourceside);
				}

				// Update line
				if(ls.Line.Front != null)ls.Line.Front.RemoveUnneededTextures(wassinglesided, false, wassinglesided);
				if(ls.Line.Back != null) ls.Line.Back.RemoveUnneededTextures(wassinglesided, false, wassinglesided);

				// Apply single/double sided flags if the double-sided-ness changed
				if( (wassinglesided && ((ls.Line.Front != null) && (ls.Line.Back != null))) ||
					(!wassinglesided && ((ls.Line.Front == null) || (ls.Line.Back == null))))
					ls.Line.ApplySidedFlags();
			}

			// Return the new sector
			return newsector;
		}


		// This joins a sector with the given lines and sides. Returns null when operation could not be completed.
		public static Sector JoinSector(List<LinedefSide> alllines, Sidedef original)
		{
			SidedefSettings sourceside = new SidedefSettings();
			
			// Take settings fro mthe original side
			TakeSidedefSettings(ref sourceside, original);

			// Use defaults where no settings could be found
			TakeSidedefDefaults(ref sourceside);

			// Go for all sides to make sidedefs
			foreach(LinedefSide ls in alllines)
			{
				if(ls.Front)
				{
					// Create sidedef if needed
					if(ls.Line.Front == null)
					{
						Sidedef sd = General.Map.Map.CreateSidedef(ls.Line, true, original.Sector);
						if(sd == null) return null;
						ApplyDefaultsToSidedef(ls.Line.Front, sourceside);
						ls.Line.ApplySidedFlags();
						
						// We must remove the (now useless) middle texture on the other side
						if(ls.Line.Back != null) ls.Line.Back.RemoveUnneededTextures(true, true, true);
					}
					// Added 23-9-08, can we do this or will it break things?
					else if(!original.Sector.IsDisposed) //mxd
					{
						// Link to the new sector
						ls.Line.Front.SetSector(original.Sector);
					}
				}
				else
				{
					// Create sidedef if needed
					if(ls.Line.Back == null)
					{
						Sidedef sd = General.Map.Map.CreateSidedef(ls.Line, false, original.Sector);
						if(sd == null) return null;
						ApplyDefaultsToSidedef(ls.Line.Back, sourceside);
						ls.Line.ApplySidedFlags();

						// We must remove the (now useless) middle texture on the other side
						if(ls.Line.Front != null) ls.Line.Front.RemoveUnneededTextures(true, true, true);
					}
					// Added 23-9-08, can we do this or will it break things?
					else if(!original.Sector.IsDisposed) //mxd
					{
						// Link to the new sector
						ls.Line.Back.SetSector(original.Sector);
					}
				}
			}

			// Return the new sector
			return original.Sector;
		}

		//mxd. This merges sectors, which have less than 3 sides, with surrounding sectors.
		//Most of the logic is taken from MakeSectorsMode.
		//Vector2D is sector's center BEFORE sides were removed.
		//See VerticesMode.DeleteItem() for usage example
		public static void MergeInvalidSectors(Dictionary<Sector, Vector2D> toMerge) 
		{
			foreach(KeyValuePair<Sector, Vector2D> group in toMerge) 
			{
				if(!group.Key.IsDisposed && group.Key.Sidedefs.Count > 0 && group.Key.Sidedefs.Count < 3) 
				{
					group.Key.Dispose();

					List<LinedefSide> sides = Tools.FindPotentialSectorAt(group.Value);

					if(sides != null) 
					{
						// Mark the lines we are going to use for this sector
						General.Map.Map.ClearAllMarks(true);
						foreach(LinedefSide ls in sides) ls.Line.Marked = false;
						List<Linedef> oldlines = General.Map.Map.GetMarkedLinedefs(true);

						// Make the sector
						Sector s = Tools.MakeSector(sides, oldlines, false);

						if(s != null) 
						{
							// Now we go for all the lines along the sector to
							// see if they only have a back side. In that case we want
							// to flip the linedef to that it only has a front side.
							foreach(Sidedef sd in s.Sidedefs) 
							{
								if((sd.Line.Front == null) && (sd.Line.Back != null)) 
								{
									// Flip linedef
									sd.Line.FlipVertices();
									sd.Line.FlipSidedefs();
								}
							}

							General.Map.Data.UpdateUsedTextures();
						}
					}
				}
			}
		}

		// This takes default settings if not taken yet
		private static void TakeSidedefDefaults(ref SidedefSettings settings)
		{
			// Use defaults where no settings could be found
			if(settings.newtexhigh == null) settings.newtexhigh = General.Map.Options.DefaultTopTexture;
			if(settings.newtexmid == null) settings.newtexmid = General.Map.Options.DefaultWallTexture;
			if(settings.newtexlow == null) settings.newtexlow = General.Map.Options.DefaultBottomTexture;
		}

		// This takes sidedef settings if not taken yet
		private static void TakeSidedefSettings(ref SidedefSettings settings, Sidedef side)
		{
			if((side.LongHighTexture != MapSet.EmptyLongName) && (settings.newtexhigh == null))
				settings.newtexhigh = side.HighTexture;
			if((side.LongMiddleTexture != MapSet.EmptyLongName) && (settings.newtexmid == null))
				settings.newtexmid = side.MiddleTexture;
			if((side.LongLowTexture != MapSet.EmptyLongName) && (settings.newtexlow == null))
				settings.newtexlow = side.LowTexture;
		}
		
		// This applies defaults to a sidedef
		private static void ApplyDefaultsToSidedef(Sidedef sd, SidedefSettings defaults)
		{
			if(sd.HighRequired() && sd.LongHighTexture == MapSet.EmptyLongName) sd.SetTextureHigh(defaults.newtexhigh); //mxd
			if(sd.MiddleRequired() && sd.LongMiddleTexture == MapSet.EmptyLongName) sd.SetTextureMid(defaults.newtexmid); //mxd
			if(sd.LowRequired() && sd.LongLowTexture == MapSet.EmptyLongName) sd.SetTextureLow(defaults.newtexlow); //mxd
		}

		//mxd. This applies overrides to a sidedef
		private static void ApplyOverridesToSidedef(Sidedef sd) 
		{
			if(sd.HighRequired() && General.Map.Options.OverrideTopTexture) sd.SetTextureHigh(General.Map.Options.DefaultTopTexture);
			if(sd.MiddleRequired() && General.Map.Options.OverrideMiddleTexture) sd.SetTextureMid(General.Map.Options.DefaultWallTexture);
			if(sd.LowRequired() && General.Map.Options.OverrideBottomTexture) sd.SetTextureLow(General.Map.Options.DefaultBottomTexture);
		}
		
		#endregion
		
		#region ================== Sector Labels
		
		// This finds the ideal label positions for a sector
		public static List<LabelPositionInfo> FindLabelPositions(Sector s)
		{
			List<LabelPositionInfo> positions = new List<LabelPositionInfo>(2);
			int islandoffset = 0;
			
			// Do we have a triangulation?
			Triangulation triangles = s.Triangles;
			if(triangles != null)
			{
				// Go for all islands
				for(int i = 0; i < triangles.IslandVertices.Count; i++)
				{
					Dictionary<Sidedef, Linedef> sides = new Dictionary<Sidedef, Linedef>(triangles.IslandVertices[i] >> 1);
					List<Vector2D> candidatepositions = new List<Vector2D>(triangles.IslandVertices[i] >> 1);
					double founddistance = double.MinValue;
					Vector2D foundposition = new Vector2D();
					double minx = double.MaxValue;
					double miny = double.MaxValue;
					double maxx = double.MinValue;
					double maxy = double.MinValue;
					
					// Make candidate lines that are not along sidedefs
					// We do this before testing the candidate against the sidedefs so that
					// we can collect the relevant sidedefs first in the same run
					for(int t = 0; t < triangles.IslandVertices[i]; t += 3)
					{
						int triangleoffset = islandoffset + t;
						Vector2D v1 = triangles.Vertices[triangleoffset + 2];
						Sidedef sd = triangles.Sidedefs[triangleoffset + 2];
						for(int v = 0; v < 3; v++)
						{
							Vector2D v2 = triangles.Vertices[triangleoffset + v];
							
							// Not along a sidedef? Then this line is across the sector
							// and guaranteed to be inside the sector!
							if(sd == null)
							{
								// Make the line
								candidatepositions.Add(v1 + (v2 - v1) * 0.5f);
							}
							else
							{
								// This sidedefs is part of this island and must be checked
								// so add it to the dictionary
								sides[sd] = sd.Line;
							}
							
							// Make bbox of this island
							minx = Math.Min(minx, v1.x);
							miny = Math.Min(miny, v1.y);
							maxx = Math.Max(maxx, v1.x);
							maxy = Math.Max(maxy, v1.y);
							
							// Next
							sd = triangles.Sidedefs[triangleoffset + v];
							v1 = v2;
						}
					}

					// Any candidate lines found at all?
					if(candidatepositions.Count > 0)
					{
						// Start with the first line
						foreach(Vector2D candidatepos in candidatepositions)
						{
							// Check distance against other lines
							double smallestdist = int.MaxValue;
							foreach(KeyValuePair<Sidedef, Linedef> sd in sides)
							{
								// Check the distance
								double distance = sd.Value.DistanceToSq(candidatepos, true);
								smallestdist = Math.Min(smallestdist, distance);
							}
							
							// Keep this candidate if it is better than previous
							if(smallestdist > founddistance)
							{
								foundposition = candidatepos;
								founddistance = smallestdist;
							}
						}
						
						// No cceptable line found, just use the first!
						positions.Add(new LabelPositionInfo(foundposition, Math.Sqrt(founddistance)));
					}
					else
					{
						// No candidate lines found.
						
						// Check to see if the island is a triangle
						if(triangles.IslandVertices[i] == 3)
						{
							// Use the center of the triangle
							// TODO: Use the 'incenter' instead, see http://mathworld.wolfram.com/Incenter.html
							Vector2D v = (triangles.Vertices[islandoffset] + triangles.Vertices[islandoffset + 1] + triangles.Vertices[islandoffset + 2]) / 3.0f;
							double d = Line2D.GetDistanceToLineSq(triangles.Vertices[islandoffset], triangles.Vertices[islandoffset + 1], v, false);
							d = Math.Min(d, Line2D.GetDistanceToLineSq(triangles.Vertices[islandoffset + 1], triangles.Vertices[islandoffset + 2], v, false));
							d = Math.Min(d, Line2D.GetDistanceToLineSq(triangles.Vertices[islandoffset + 2], triangles.Vertices[islandoffset], v, false));
							positions.Add(new LabelPositionInfo(v, Math.Sqrt(d)));
						}
						else
						{
							// Use the center of this island.
							double d = Math.Min((maxx - minx) * 0.5f, (maxy - miny) * 0.5f);
							positions.Add(new LabelPositionInfo(new Vector2D(minx + (maxx - minx) * 0.5f, miny + (maxy - miny) * 0.5f), d));
						}
					}
					
					// Done with this island
					islandoffset += triangles.IslandVertices[i];
				}
			}
			else
			{
				// No triangulation was made. FAIL!
				General.Fail("No triangulation exists for sector " + s + " Triangulation is required to create label positions for a sector.");
			}
			
			// Done
			return positions;
		}
		
		#endregion

		#region ================== Drawing

		//mxd
		public static bool DrawLines(IList<DrawnVertex> points) 
		{
			return DrawLines(points, false, false);
		}
		
		/// <summary>
		/// This draws lines with the given points. Note that this tool removes any existing geometry
		/// marks and marks the new lines and vertices when done. Also marks the sectors that were added.
		/// Returns false when the drawing failed.
		/// </summary>
		public static bool DrawLines(IList<DrawnVertex> points, bool useOverrides, bool autoAlignTextureOffsets)
		{
			List<Vertex> newverts = new List<Vertex>();
			List<Vertex> intersectverts = new List<Vertex>();
			List<Linedef> newlines = new List<Linedef>();
			List<Linedef> oldlines = new List<Linedef>(General.Map.Map.Linedefs);
			List<Sidedef> insidesides = new List<Sidedef>();
			List<Vertex> mergeverts = new List<Vertex>();
			List<Vertex> nonmergeverts = new List<Vertex>(General.Map.Map.Vertices);
			MapSet map = General.Map.Map;

			General.Map.Map.ClearAllMarks(false);
			
			// Any points to do?
			if(points.Count > 0)
			{
				/***************************************************\
					Create the drawing
				\***************************************************/

				// Make first vertex
				Vertex v1 = map.CreateVertex(points[0].pos);
				if(v1 == null) return false;
				v1.Marked = true;

				// Keep references
				newverts.Add(v1);
				if(points[0].stitch) mergeverts.Add(v1); else nonmergeverts.Add(v1);

				// Go for all other points
				for(int i = 1; i < points.Count; i++)
				{
					// Create vertex for point
					Vertex v2 = map.CreateVertex(points[i].pos);
					if(v2 == null) return false;
					v2.Marked = true;

					// Keep references
					newverts.Add(v2);
					if(points[i].stitch) mergeverts.Add(v2); else nonmergeverts.Add(v2);

					// Create line between point and previous
					Linedef ld = map.CreateLinedef(v1, v2);
					if(ld == null) return false;
					ld.Marked = true;
					ld.ApplySidedFlags();
					ld.UpdateCache();
					newlines.Add(ld);

					// Should we split this line to merge with intersecting lines?
					if(points[i - 1].stitchline && points[i].stitchline)
					{
						// Check if any other lines intersect this line
						List<double> intersections = new List<double>();
						Line2D measureline = ld.Line;
						HashSet<Linedef> processed = new HashSet<Linedef>(); //mxd

						//mxd
						foreach(Sector s in map.Sectors) 
						{
							//line intersects with sector's bounding box?
							if((MapSet.GetCSFieldBits(measureline.v1, s.BBox) & MapSet.GetCSFieldBits(measureline.v2, s.BBox)) == 0) 
							{
								foreach(Sidedef side in s.Sidedefs) 
								{
									if(processed.Contains(side.Line)) continue;
									if(side.Line == ld) continue;

									double u;
									if(side.Line.Line.GetIntersection(measureline, out u)) 
									{
										if(double.IsNaN(u) || (u <= 0.0f) || (u >= 1.0f)) continue;

										//mxd. Skip intersection if both start and end of one line are closer than given distance from the other line.
										// This allows to avoid creating "unexpected" splits when drawing on top of non-cardinal lines.

										//mxd. Check if both ends of measureline are too close to side.Line.Line
										bool valid = (side.Line.Line.GetDistanceToLineSq(measureline.v1, true) > MINIMUM_INTERSECTION_DISTANCE ||
													  side.Line.Line.GetDistanceToLineSq(measureline.v2, true) > MINIMUM_INTERSECTION_DISTANCE);
										
										//mxd. Check if both ends of side.Line.Line are too close to measureline
										valid = (valid && (measureline.GetDistanceToLineSq(side.Line.Line.v1, true) > MINIMUM_INTERSECTION_DISTANCE ||
														   measureline.GetDistanceToLineSq(side.Line.Line.v2, true) > MINIMUM_INTERSECTION_DISTANCE));

										// Store inersection
										if(valid) intersections.Add(u);
									}

									processed.Add(side.Line);
								}
							}
						}

						// Sort the intersections
						intersections.Sort();

						// Go for all found intersections
						Linedef splitline = ld;
						foreach(double u in intersections)
						{
							// Calculate exact coordinates where to split
							// We use measureline for this, because the original line
							// may already have changed in length due to a previous split
							Vector2D splitpoint = measureline.GetCoordinatesAt(u);

							// Make the vertex
							Vertex splitvertex = map.CreateVertex(splitpoint);
							if(splitvertex == null) return false;
							splitvertex.Marked = true;
							newverts.Add(splitvertex);
							mergeverts.Add(splitvertex);			// <-- add to merge?
							intersectverts.Add(splitvertex);
							
							// The Split method ties the end of the original line to the given
							// vertex and starts a new line at the given vertex, so continue
							// splitting with the new line, because the intersections are sorted
							// from low to high (beginning at the original line start)
							splitline = splitline.Split(splitvertex);
							if(splitline == null) return false;
							splitline.ApplySidedFlags();
							newlines.Add(splitline);
						}
					}

					// Next
					v1 = v2;
				}

				// Join merge vertices so that overlapping vertices in the draw become one.
				map.BeginAddRemove();
				MapSet.JoinVertices(mergeverts, MapSet.STITCH_DISTANCE); //mxd
				map.EndAddRemove();

				// Filter old lines and vertices by edited area
				RectangleF editarea = MapSet.CreateArea(newlines);
				editarea = MapSet.IncreaseArea(editarea, mergeverts);
				editarea.Inflate(1.0f, 1.0f);
				oldlines = new List<Linedef>(MapSet.FilterByArea(oldlines, ref editarea));
				nonmergeverts = new List<Vertex>(MapSet.FilterByArea(nonmergeverts, ref editarea));

				/***************************************************\
					Find a way to close the drawing
				\***************************************************/

				// We prefer a closed polygon, because then we can determine the interior properly
				// Check if the two ends of the polygon are closed
				bool splittingonly = false;
				bool drawingclosed = false; //mxd
				if(newlines.Count > 0)
				{
					Linedef firstline = newlines[0];
					Linedef lastline = newlines[newlines.Count - 1];
					drawingclosed = (firstline.Start == lastline.End);
					if(!drawingclosed)
					{
						// When not closed, we will try to find a path to close it.
						// But first we check if any of our new lines are inside existing sectors, because
						// if they are then we are splitting sectors and cannot accurately find a closed path
						// to close our polygon. In that case, we want to do sector splits only.
						foreach(Linedef ld in newlines)
						{
							Vector2D ldcp = ld.GetCenterPoint();
							Linedef nld = MapSet.NearestLinedef(oldlines, ldcp);
							if(nld != null)
							{
								double ldside = nld.SideOfLine(ldcp);
								if(ldside < 0.0f)
								{
									if(nld.Front != null)
									{
										splittingonly = true;
										break;
									}
								}
								else if(ldside > 0.0f)
								{
									if(nld.Back != null)
									{
										splittingonly = true;
										break;
									}
								}
								/*else
								{
									// We can't tell, so lets ignore this for now.
								}*/
							}
						}

						// Not splitting only?
						if(!splittingonly)
						{
							// First and last vertex stitch with geometry?
							if(points[0].stitch && points[points.Count - 1].stitch)
							{
								List<LinedefSide> startpoints = new List<LinedefSide>();
								List<LinedefSide> endpoints = new List<LinedefSide>();

								// Find out where the start will stitch and create test points
								Linedef l1 = MapSet.NearestLinedefRange(oldlines, firstline.Start.Position, MapSet.STITCH_DISTANCE);
								Vertex vv1 = null;
								if(l1 != null)
								{
									startpoints.Add(new LinedefSide(l1, true));
									startpoints.Add(new LinedefSide(l1, false));
								}
								else
								{
									// Not stitched with a linedef, so check if it will stitch with a vertex
									vv1 = MapSet.NearestVertexSquareRange(nonmergeverts, firstline.Start.Position, MapSet.STITCH_DISTANCE);
									if((vv1 != null) && (vv1.Linedefs.Count > 0))
									{
										// Now we take the two linedefs with adjacent angles to the drawn line
										List<Linedef> lines = new List<Linedef>(vv1.Linedefs);
										lines.Sort(new LinedefAngleSorter(firstline, true, firstline.Start));
										startpoints.Add(new LinedefSide(lines[0], true));
										startpoints.Add(new LinedefSide(lines[0], false));
										lines.Sort(new LinedefAngleSorter(firstline, false, firstline.Start));
										startpoints.Add(new LinedefSide(lines[0], true));
										startpoints.Add(new LinedefSide(lines[0], false));
									}
								}

								// Find out where the end will stitch and create test points
								Linedef l2 = MapSet.NearestLinedefRange(oldlines, lastline.End.Position, MapSet.STITCH_DISTANCE);
								Vertex vv2 = null;
								if(l2 != null)
								{
									endpoints.Add(new LinedefSide(l2, true));
									endpoints.Add(new LinedefSide(l2, false));
								}
								else
								{
									// Not stitched with a linedef, so check if it will stitch with a vertex
									vv2 = MapSet.NearestVertexSquareRange(nonmergeverts, lastline.End.Position, MapSet.STITCH_DISTANCE);
									if((vv2 != null) && (vv2.Linedefs.Count > 0))
									{
										// Now we take the two linedefs with adjacent angles to the drawn line
										List<Linedef> lines = new List<Linedef>(vv2.Linedefs);
										lines.Sort(new LinedefAngleSorter(firstline, true, lastline.End));
										endpoints.Add(new LinedefSide(lines[0], true));
										endpoints.Add(new LinedefSide(lines[0], false));
										lines.Sort(new LinedefAngleSorter(firstline, false, lastline.End));
										endpoints.Add(new LinedefSide(lines[0], true));
										endpoints.Add(new LinedefSide(lines[0], false));
									}
								}

								// Found any start and end points?
								if((startpoints.Count > 0) && (endpoints.Count > 0))
								{
									List<LinedefSide> shortestpath = null;

									// Both stitched to the same line?
									if((l1 == l2) && (l1 != null))
									{
										// Then just connect the two
										shortestpath = new List<LinedefSide>();
										shortestpath.Add(new LinedefSide(l1, true));
									}
									// One stitched to a line and the other to a vertex of that line?
									else if((l1 != null) && (vv2 != null) && ((l1.Start == vv2) || (l1.End == vv2)))
									{
										// Then just connect the two
										shortestpath = new List<LinedefSide>();
										shortestpath.Add(new LinedefSide(l1, true));
									}
									// The other stitched to a line and the first to a vertex of that line?
									else if((l2 != null) && (vv1 != null) && ((l2.Start == vv1) || (l2.End == vv1)))
									{
										// Then just connect the two
										shortestpath = new List<LinedefSide>();
										shortestpath.Add(new LinedefSide(l2, true));
									}
									else
									{
										// Find the shortest, closest path between start and end points
										foreach(LinedefSide startp in startpoints)
										{
											foreach(LinedefSide endp in endpoints)
											{
												List<LinedefSide> p = Tools.FindClosestPath(startp.Line, startp.Front, endp.Line, endp.Front, true);
												if((p != null) && ((shortestpath == null) || (p.Count < shortestpath.Count))) shortestpath = p;
												p = Tools.FindClosestPath(endp.Line, endp.Front, startp.Line, startp.Front, true);
												if((p != null) && ((shortestpath == null) || (p.Count < shortestpath.Count))) shortestpath = p;
											}
										}
									}

									// Found a path?
									if(shortestpath != null)
									{
										// Check which direction the path goes in
										bool pathforward = false;
										foreach(LinedefSide startp in startpoints)
										{
											if(shortestpath[0].Line == startp.Line)
											{
												pathforward = true;
												break;
											}
										}

										// TEST
										/*
										General.Map.Renderer2D.StartOverlay(true);
										foreach(LinedefSide lsd in shortestpath)
										{
											General.Map.Renderer2D.RenderLine(lsd.Line.Start.Position, lsd.Line.End.Position, 2, new PixelColor(255, 0, 255, 0), true);
										}
										General.Map.Renderer2D.Finish();
										General.Map.Renderer2D.Present();
										Thread.Sleep(1000);
										*/
										
										// Begin at first vertex in path
										v1 = (pathforward ? firstline.Start : lastline.End);

										// Go for all vertices in the path to make additional lines
										for(int i = 1; i < shortestpath.Count; i++)
										{
											// Get the next position
											Vector2D v2pos = shortestpath[i].Front ? shortestpath[i].Line.Start.Position : shortestpath[i].Line.End.Position;

											// Make the new vertex
											Vertex v2 = map.CreateVertex(v2pos);
											if(v2 == null) return false;
											v2.Marked = true;
											mergeverts.Add(v2);

											// Make the line
											Linedef ld = map.CreateLinedef(v1, v2);
											if(ld == null) return false;
											ld.Marked = true;
											ld.ApplySidedFlags();
											ld.UpdateCache();
											newlines.Add(ld);

											// Next
											v1 = v2;
										}

										// Make the final line
										Linedef lld;
										if(pathforward)
											lld = map.CreateLinedef(v1, lastline.End);
										else
											lld = map.CreateLinedef(v1, firstline.Start);

										if(lld == null) return false;
										
										// Setup line
										lld.Marked = true;
										lld.ApplySidedFlags();
										lld.UpdateCache();
										newlines.Add(lld);

										// Drawing is now closed
										drawingclosed = true;

										// Join merge vertices so that overlapping vertices in the draw become one.
										MapSet.JoinVertices(mergeverts, MapSet.STITCH_DISTANCE); //mxd
									}
								}
							}
						}
					}
				}

				// Merge intersetion vertices with the new lines. This completes the
				// self intersections for which splits were made above.
				map.Update(true, false);
				map.BeginAddRemove();
				MapSet.SplitLinesByVertices(newlines, intersectverts, MapSet.STITCH_DISTANCE, null);
				MapSet.SplitLinesByVertices(newlines, mergeverts, MapSet.STITCH_DISTANCE, null);
				map.EndAddRemove();
				
				/***************************************************\
					Determine drawing interior
				\***************************************************/

				// In step 3 we will make sectors on the interior sides and join sectors on the
				// exterior sides, but because the user could have drawn counterclockwise or just
				// some weird polygon. The following code figures out the interior side of all
				// new lines.
				map.Update(true, false);
				foreach(Linedef ld in newlines)
				{
					// Find closest path starting with the front of this linedef
					List<LinedefSide> pathlines = Tools.FindClosestPath(ld, true, true);
					if(pathlines != null)
					{
						// Make polygon
						LinedefTracePath tracepath = new LinedefTracePath(pathlines);
						EarClipPolygon pathpoly = tracepath.MakePolygon(true);
						
						// Check if the front of the line is outside the polygon
						if((pathpoly.CalculateArea() > 0.001f) && !pathpoly.Intersect(ld.GetSidePoint(true)))
						{
							// Now trace from the back side of the line to see if
							// the back side lies in the interior. I don't want to
							// flip the line if it is not helping.

							// Find closest path starting with the back of this linedef
							pathlines = Tools.FindClosestPath(ld, false, true);
							if(pathlines != null)
							{
								// Make polygon
								tracepath = new LinedefTracePath(pathlines);
								pathpoly = tracepath.MakePolygon(true);

								// Check if the front of the line is inside the polygon
								ld.FrontInterior = (pathpoly.CalculateArea() < 0.001f) || pathpoly.Intersect(ld.GetSidePoint(true));
							}
							else
							{
								ld.FrontInterior = true;
							}
						}
						else
						{
							ld.FrontInterior = true;
						}
					}
					else
					{
						ld.FrontInterior = true;
					}
				}

				/***************************************************\
					Merge the new geometry
				\***************************************************/

				// Mark only the vertices that should be merged
				map.ClearMarkedVertices(false);
				foreach(Vertex v in mergeverts) v.Marked = true;

				// Before this point, the new geometry is not linked with the existing geometry.
				// Now perform standard geometry stitching to merge the new geometry with the rest
				// of the map. The marked vertices indicate the new geometry.
				if (!map.StitchGeometry())
					return false;
				map.Update(true, false);

				// Find our new lines again, because they have been merged with the other geometry
				// but their Marked property is copied where they have joined.
				newlines = map.GetMarkedLinedefs(true);
				
				// Remove any disposed old lines
				List<Linedef> prevoldlines = oldlines;
				oldlines = new List<Linedef>(prevoldlines.Count);
				foreach(Linedef ld in prevoldlines)
					if(!ld.IsDisposed) oldlines.Add(ld);
				
				/***************************************************\
					Join and create new sectors
				\***************************************************/

				// The code below atempts to create sectors on the interior sides of the drawn
				// geometry and joins sectors on the other sides of the drawn geometry.
				// This code does not change any geometry, it only makes/updates sidedefs.
				bool sidescreated = false;
				bool[] frontsdone = new bool[newlines.Count];
				bool[] backsdone = new bool[newlines.Count];
				for(int i = 0; i < newlines.Count; i++)
				{
					Linedef ld = newlines[i];

					// Interior not done yet?
					if((ld.FrontInterior && !frontsdone[i]) || (!ld.FrontInterior && !backsdone[i]))
					{
						// Find a way to create a sector here
						List<LinedefSide> sectorlines = Tools.FindPotentialSectorAt(ld, ld.FrontInterior);
						if(sectorlines != null)
						{
							sidescreated = true;

							// When none of the linedef sides exist yet, this is a true new
							// sector that will be created out of the void!
							bool istruenewsector = true;
							foreach(LinedefSide ls in sectorlines)
							{
								if((ls.Front && (ls.Line.Front != null)) ||
								   (!ls.Front && (ls.Line.Back != null)))
								{
									istruenewsector = false;
									break;
								}
							}

							// But we don't want to create sectors out of the void when we
							// decided that we only want to split sectors.
							if(!istruenewsector || !splittingonly)
							{
								// Make the new sector
								//mxd. Apply sector overrides only if a closed drawing is created
								Sector newsector = Tools.MakeSector(sectorlines, oldlines, (useOverrides && drawingclosed && newlines.Count > 2));
								if(newsector == null) return false;

								if(istruenewsector) newsector.Marked = true;

								// Go for all sidedefs in this new sector
								foreach(Sidedef sd in newsector.Sidedefs)
								{
									// Keep list of sides inside created sectors
									insidesides.Add(sd);

									// Side matches with a side of our new lines?
									int lineindex = newlines.IndexOf(sd.Line);
									if(lineindex > -1)
									{
										// Mark this side as done
										if(sd.IsFront)
											frontsdone[lineindex] = true;
										else
											backsdone[lineindex] = true;
									}
								}
							}
						}
					}

					// Exterior not done yet?
					if((ld.FrontInterior && !backsdone[i]) || (!ld.FrontInterior && !frontsdone[i]))
					{
						// Find a way to create a sector here
						List<LinedefSide> sectorlines = Tools.FindPotentialSectorAt(ld, !ld.FrontInterior);
						if(sectorlines != null)
						{
							// Check if any of the surrounding lines originally have sidedefs we can join
							Sidedef joinsidedef = null;
							foreach(LinedefSide ls in sectorlines)
							{
								if(ls.Front && (ls.Line.Front != null))
								{
									joinsidedef = ls.Line.Front;
									break;
								}
								if(!ls.Front && (ls.Line.Back != null))
								{
									joinsidedef = ls.Line.Back;
									break;
								}
							}

							// Join?
							if(joinsidedef != null)
							{
								sidescreated = true;

								// We only want to modify our new lines when joining a sector
								// (or it may break nearby self-referencing sectors)
								List<LinedefSide> newsectorlines = new List<LinedefSide>(sectorlines.Count);
								foreach(LinedefSide sd in sectorlines)
								{
									// Side matches with a side of our new lines?
									int lineindex = newlines.IndexOf(sd.Line);
									if(lineindex > -1)
									{
										// Add to list
										newsectorlines.Add(sd);
										
										// Mark this side as done
										if(sd.Front)
											frontsdone[lineindex] = true;
										else
											backsdone[lineindex] = true;
									}
								}
								
								// Have our new lines join the existing sector
								if(Tools.JoinSector(newsectorlines, joinsidedef) == null)
									return false;
							}
						}
					}
				}

				/***************************************************\
					Corrections and clean up
				\***************************************************/

				// Make corrections for backward linedefs
				MapSet.FlipBackwardLinedefs(newlines);

				// Check if any of our new lines have sides
				if(sidescreated)
				{
					// Then remove the lines which have no sides at all
					for(int i = newlines.Count - 1; i >= 0; i--)
					{
						// Remove the line if it has no sides
						if((newlines[i].Front != null) || (newlines[i].Back != null)) continue; 
						newlines[i].Dispose();
					}

					//mxd. Apply texture overrides
					if(useOverrides) 
					{
						// If new sectors are created, apply overrides to the sides of these sectors, otherwise, apply overrides to all new lines
						if(insidesides.Count > 0) 
						{
							foreach(Sidedef side in insidesides) ApplyOverridesToSidedef(side);
						} 
						else 
						{
							foreach(Linedef l in newlines) 
							{
								if(l.IsDisposed) continue;
								if(!newverts.Contains(l.Start) || !newverts.Contains(l.End)) continue;
								ApplyOverridesToSidedef(l.Front);
								if(l.Back != null) ApplyOverridesToSidedef(l.Back);
							}
						}
					}

					//mxd. Auto-align new lines
					if(autoAlignTextureOffsets && newlines.Count > 1 && !splittingonly) 
					{
						List<List<Linedef>> strips = new List<List<Linedef>>();
						strips.Add(new List<Linedef> { newlines[0] });

						for(int i = 1; i < newlines.Count; i++) 
						{
							//skip double-sided line if it doesn't have lower or upper parts or they are not part of newly created sectors
							if(newlines[i].Back != null
								&& (((!newlines[i].Front.LowRequired() && !newlines[i].Front.HighRequired()) || !insidesides.Contains(newlines[i].Front))
								&& ((!newlines[i].Back.LowRequired() && !newlines[i].Back.HighRequired()) || !insidesides.Contains(newlines[i].Back))))
								continue;

							bool added = false;
							foreach(List<Linedef> strip in strips) 
							{
								if(newlines[i].Start == strip[0].Start || newlines[i].End == strip[0].Start) 
								{
									strip.Insert(0, newlines[i]);
									added = true;
									break;
								}

								if(newlines[i].Start == strip[strip.Count - 1].End || newlines[i].End == strip[strip.Count - 1].End) 
								{
									strip.Add(newlines[i]);
									added = true;
									break;
								}
							}

							if(!added) strips.Add(new List<Linedef> { newlines[i] });
						}

						foreach(List<Linedef> strip in strips) 
						{
							if(strip.Count < 2) continue;
							AutoAlignLinedefStrip(strip);
						}
					}
				}

				// Mark new geometry only
				General.Map.Map.ClearMarkedLinedefs(false);
				General.Map.Map.ClearMarkedVertices(false);
				foreach(Vertex v in newverts) v.Marked = true;
				foreach(Linedef l in newlines) l.Marked = true;
			}

			return true;
		}

		//mxd
		private static void AutoAlignLinedefStrip(List<Linedef> strip) 
		{
			if(strip.Count < 2) return;

			double totalLength = 0f;
			foreach(Linedef l in strip) totalLength += l.Length;

			if(General.Map.UDMF && General.Map.Config.UseLocalSidedefTextureOffsets)
				AutoAlignTexturesOnSidesUdmf(strip, totalLength, (strip[0].End != strip[1].Start));
			else
				AutoAlignTexturesOnSides(strip, totalLength, (strip[0].End != strip[1].Start));	
		}

		//mxd
		private static void AutoAlignTexturesOnSides(List<Linedef> lines, double totalLength, bool reversed) 
		{
			double curLength = 0f;
			
			foreach(Linedef l in lines) 
			{
				if(l.Front != null) 
				{
					ImageData texture = null;

					if(l.Front.MiddleRequired() && l.Front.LongMiddleTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Front.LongMiddleTexture))
						texture = General.Map.Data.GetTextureImage(l.Front.LongMiddleTexture);
					else if(l.Front.HighRequired() && l.Front.LongHighTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Front.LongHighTexture))
						texture = General.Map.Data.GetTextureImage(l.Front.LongHighTexture);
					else if(l.Front.LowRequired() && l.Front.LongLowTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Front.LongLowTexture))
						texture = General.Map.Data.GetTextureImage(l.Front.LongLowTexture);

					if(texture != null && texture.IsImageLoaded)
						l.Front.OffsetX = (int)Math.Round((reversed ? totalLength - curLength - l.Length : curLength)) % texture.Width;
				}

				if(l.Back != null) 
				{
					ImageData texture = null;

					if(l.Back.MiddleRequired() && l.Back.LongMiddleTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Back.LongMiddleTexture))
						texture = General.Map.Data.GetTextureImage(l.Back.LongMiddleTexture);
					else if(l.Back.HighRequired() && l.Back.LongHighTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Back.LongHighTexture))
						texture = General.Map.Data.GetTextureImage(l.Back.LongHighTexture);
					else if(l.Back.LowRequired() && l.Back.LongLowTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Back.LongLowTexture))
						texture = General.Map.Data.GetTextureImage(l.Back.LongLowTexture);

					if(texture != null && texture.IsImageLoaded)
						l.Back.OffsetX = (int)Math.Round((reversed ? totalLength - curLength - l.Length : curLength)) % texture.Width;
				}

				curLength += l.Length;
			}
		}

		//mxd
		private static void AutoAlignTexturesOnSidesUdmf(List<Linedef> lines, double totalLength, bool reversed) 
		{
			double curLength = 0f;

			foreach(Linedef l in lines) 
			{
				if(l.Front != null) 
				{
					if(l.Front.MiddleRequired() && l.Front.LongMiddleTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Front.LongMiddleTexture)) 
					{
						ImageData texture = General.Map.Data.GetTextureImage(l.Front.LongMiddleTexture);
						double offset = (int)Math.Round((reversed ? totalLength - curLength - l.Length : curLength));
						if(texture.IsImageLoaded) offset %= texture.Width;
						if(offset > 0) UniFields.SetFloat(l.Front.Fields, "offsetx_mid", offset);
					}

					if(l.Front.HighRequired() && l.Front.LongHighTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Front.LongHighTexture)) 
					{
						ImageData texture = General.Map.Data.GetTextureImage(l.Front.LongHighTexture);
						double offset = (int)Math.Round((reversed ? totalLength - curLength - l.Length : curLength));
						if(texture.IsImageLoaded) offset %= texture.Width;
						if(offset > 0) UniFields.SetFloat(l.Front.Fields, "offsetx_top", offset);
					}

					if(l.Front.LowRequired() && l.Front.LongLowTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Front.LongLowTexture)) 
					{
						ImageData texture = General.Map.Data.GetTextureImage(l.Front.LongLowTexture);
						double offset = (int)Math.Round((reversed ? totalLength - curLength - l.Length : curLength));
						if(texture.IsImageLoaded) offset %= texture.Width;
						if(offset > 0) UniFields.SetFloat(l.Front.Fields, "offsetx_bottom", offset);
					}
				}

				if(l.Back != null) 
				{
					if(l.Back.MiddleRequired() && l.Back.LongMiddleTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Back.LongMiddleTexture)) 
					{
						ImageData texture = General.Map.Data.GetTextureImage(l.Back.LongMiddleTexture);
						double offset = (int)Math.Round((reversed ? totalLength - curLength - l.Length : curLength));
						if(texture.IsImageLoaded) offset %= texture.Width;
						if(offset > 0) UniFields.SetFloat(l.Back.Fields, "offsetx_mid", offset);
					}

					if(l.Back.HighRequired() && l.Back.LongHighTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Back.LongHighTexture)) 
					{
						ImageData texture = General.Map.Data.GetTextureImage(l.Back.LongHighTexture);
						double offset = (int)Math.Round((reversed ? totalLength - curLength - l.Length : curLength));
						if(texture.IsImageLoaded) offset %= texture.Width;
						if(offset > 0) UniFields.SetFloat(l.Back.Fields, "offsetx_top", offset);
					}

					if(l.Back.LowRequired() && l.Back.LongLowTexture != MapSet.EmptyLongName && General.Map.Data.GetTextureExists(l.Back.LongLowTexture)) 
					{
						ImageData texture = General.Map.Data.GetTextureImage(l.Back.LongLowTexture);
						double offset = (int)Math.Round((reversed ? totalLength - curLength - l.Length : curLength));
						if(texture.IsImageLoaded) offset %= texture.Width;
						if(offset > 0) UniFields.SetFloat(l.Back.Fields, "offsetx_bottom", offset);
					}
				}

				curLength += l.Length;
			}
		}
		
		#endregion

		#region ================== Flat Floodfill

		// This performs flat floodfill over sector floors or ceilings that match with the same flat
		// NOTE: This method uses the sectors marking to indicate which sides have been filled
		// When resetsectormarks is set to true, all sectors will first be marked false (not aligned).
		// Setting resetsectormarks to false is usefull to fill only within a specific selection
		// (set the marked property to true for the sectors outside the selection)
		public static void FloodfillFlats(Sector start, bool fillceilings, HashSet<long> originalflats, string fillflat, bool resetsectormarks)
		{
			Stack<Sector> todo = new Stack<Sector>(50);

			// Mark all sectors false (they will be marked true when the flat is modified)
			if(resetsectormarks) General.Map.Map.ClearMarkedSectors(false);
			
			// Begin with first sector
			if((originalflats.Contains(start.LongFloorTexture) && !fillceilings) ||
			   (originalflats.Contains(start.LongCeilTexture) && fillceilings))
			{
				todo.Push(start);
			}

			// Continue until nothing more to align
			while(todo.Count > 0)
			{
				// Get the sector to do
				Sector s = todo.Pop();
				
				// Apply new flat
				if(fillceilings) s.SetCeilTexture(fillflat);
				else s.SetFloorTexture(fillflat);
				s.Marked = true;
				
				// Go for all sidedefs to add neighbouring sectors
				foreach(Sidedef sd in s.Sidedefs)
				{
					// Sector on the other side of the line that we haven't checked yet?
					if((sd.Other != null) && !sd.Other.Sector.Marked)
					{
						Sector os = sd.Other.Sector;
						
						// Check if texture matches
						if((originalflats.Contains(os.LongFloorTexture) && !fillceilings) ||
						   (originalflats.Contains(os.LongCeilTexture) && fillceilings))
						{
							todo.Push(os);
						}
					}
				}
			}
		}

		#endregion

		#region ================== Texture Floodfill

		// This performs texture floodfill along all walls that match with the same texture
		// NOTE: This method uses the sidedefs marking to indicate which sides have been filled
		// When resetsidemarks is set to true, all sidedefs will first be marked false (not aligned).
		// Setting resetsidemarks to false is usefull to fill only within a specific selection
		// (set the marked property to true for the sidedefs outside the selection)
		public static void FloodfillTextures(Sidedef start, HashSet<long> originaltextures, string filltexture, bool resetsidemarks)
		{
			Stack<SidedefFillJob> todo = new Stack<SidedefFillJob>(50);

			// Mark all sidedefs false (they will be marked true when the texture is aligned)
			if(resetsidemarks) General.Map.Map.ClearMarkedSidedefs(false);
			
			// Begin with first sidedef
			if(SidedefTextureMatch(start, originaltextures))
			{
				SidedefFillJob first = new SidedefFillJob();
				first.sidedef = start;
				first.forward = true;
				todo.Push(first);
			}
			
			// Continue until nothing more to align
			while(todo.Count > 0)
			{
				// Get the align job to do
				SidedefFillJob j = todo.Pop();

				// Apply texturing
				if(j.sidedef.HighRequired() && originaltextures.Contains(j.sidedef.LongHighTexture)) j.sidedef.SetTextureHigh(filltexture);
				if((j.sidedef.LongMiddleTexture != MapSet.EmptyLongName || j.sidedef.MiddleRequired()) &&
				   originaltextures.Contains(j.sidedef.LongMiddleTexture)) j.sidedef.SetTextureMid(filltexture);
				if(j.sidedef.LowRequired() && originaltextures.Contains(j.sidedef.LongLowTexture)) j.sidedef.SetTextureLow(filltexture);
				
				j.sidedef.Marked = true;
				
				if(j.forward)
				{
					// Add sidedefs forward (connected to the right vertex)
					Vertex v = j.sidedef.IsFront ? j.sidedef.Line.End : j.sidedef.Line.Start;
					AddSidedefsForFloodfill(todo, v, true, originaltextures);

					// Add sidedefs backward (connected to the left vertex)
					v = j.sidedef.IsFront ? j.sidedef.Line.Start : j.sidedef.Line.End;
					AddSidedefsForFloodfill(todo, v, false, originaltextures);
				}
				else
				{
					// Add sidedefs backward (connected to the left vertex)
					Vertex v = j.sidedef.IsFront ? j.sidedef.Line.Start : j.sidedef.Line.End;
					AddSidedefsForFloodfill(todo, v, false, originaltextures);

					// Add sidedefs forward (connected to the right vertex)
					v = j.sidedef.IsFront ? j.sidedef.Line.End : j.sidedef.Line.Start;
					AddSidedefsForFloodfill(todo, v, true, originaltextures);
				}
			}
		}

		// This adds the matching, unmarked sidedefs from a vertex for texture alignment
		private static void AddSidedefsForFloodfill(Stack<SidedefFillJob> stack, Vertex v, bool forward, HashSet<long> texturelongnames)
		{
			foreach(Linedef ld in v.Linedefs)
			{
				Sidedef side1 = forward ? ld.Front : ld.Back;
				Sidedef side2 = forward ? ld.Back : ld.Front;

                // [ZZ] don't iterate the same linedef twice.
                //      
                if ((side1 != null && side1.Marked) ||
                    (side2 != null && side2.Marked)) continue;

				if((ld.Start == v) && (side1 != null) && !side1.Marked)
				{
					if(SidedefTextureMatch(side1, texturelongnames))
					{
						SidedefFillJob nj = new SidedefFillJob();
						nj.forward = forward;
						nj.sidedef = side1;
						stack.Push(nj);
					}
				}
				else if((ld.End == v) && (side2 != null) && !side2.Marked)
				{
					if(SidedefTextureMatch(side2, texturelongnames))
					{
						SidedefFillJob nj = new SidedefFillJob();
						nj.forward = forward;
						nj.sidedef = side2;
						stack.Push(nj);
					}
				}
			}
		}

		#endregion

		#region ================== Texture Alignment
		
		// This checks if any of the sidedef texture match the given texture
		/*public static bool SidedefTextureMatch(Sidedef sd, long texturelongname)
		{
			return ((sd.LongHighTexture == texturelongname) && sd.HighRequired()) ||
				   ((sd.LongLowTexture == texturelongname) && sd.LowRequired()) ||
				   ((sd.LongMiddleTexture == texturelongname) && (sd.MiddleRequired() || sd.LongMiddleTexture != MapSet.EmptyLongName)) ;
		}*/

		//mxd. This checks if any of the sidedef texture match the given textures
		public static bool SidedefTextureMatch(Sidedef sd, HashSet<long> texturelongnames)
		{
			return (texturelongnames.Contains(sd.LongHighTexture) && sd.HighRequired()) ||
				   (texturelongnames.Contains(sd.LongLowTexture) && sd.LowRequired()) ||
				   (texturelongnames.Contains(sd.LongMiddleTexture) && (sd.MiddleRequired() || sd.LongMiddleTexture != MapSet.EmptyLongName));
		}

		//mxd. This converts offsetY from/to "normalized" offset for given wall part
		public static double GetSidedefOffsetY(Sidedef side, VisualGeometryType part, double offset, double scaleY, bool fromNormalized)
		{
			switch(part)
			{
				case VisualGeometryType.WALL_UPPER:
					return GetSidedefTopOffsetY(side, offset, scaleY, fromNormalized);
				
				case VisualGeometryType.WALL_MIDDLE:
				case VisualGeometryType.WALL_MIDDLE_3D:
					return GetSidedefMiddleOffsetY(side, offset, scaleY, fromNormalized);

				case VisualGeometryType.WALL_LOWER:
					return GetSidedefBottomOffsetY(side, offset, scaleY, fromNormalized);

				default:
					throw new NotSupportedException("Tools.GetSidedefOffsetY: \"" + part + "\" geometry type is not supported!");
			}
		}

		//mxd. This converts offsetY from/to "normalized" offset for given upper wall
		public static double GetSidedefTopOffsetY(Sidedef side, double offset, double scaleY, bool fromNormalized) 
		{
			if(side.Line.IsFlagSet(General.Map.Config.UpperUnpeggedFlag) || side.Other == null || side.Other.Sector == null)
				return offset;

			// Make sure the offset doesn't go in the wrong direction
			scaleY = Math.Abs(scaleY);

			//if we don't have UpperUnpegged flag, normalize offset
			double surfaceHeight = side.GetHighHeight() * scaleY;
			return Math.Round((fromNormalized ? offset + surfaceHeight : offset - surfaceHeight), General.Map.FormatInterface.VertexDecimals);
		}

		//mxd. This converts offsetY from/to "normalized" offset for given middle wall
		public static double GetSidedefMiddleOffsetY(Sidedef side, double offset, double scaleY, bool fromNormalized) 
		{
			if(side.Sector == null) return offset;

			// Make sure the offset doesn't go in the wrong direction
			scaleY = Math.Abs(scaleY);

			// Normalize offset
			double surfaceHeight;
			if(side.Other != null && side.Other.Sector != null)
			{
				if(side.Line.IsFlagSet(General.Map.Config.PegMidtextureFlag))
				{
					// Double-sided with PegMidtextureFlag set
					surfaceHeight = (side.Sector.CeilHeight - Math.Max(side.Sector.FloorHeight, side.Other.Sector.FloorHeight)) * scaleY;
				} 
				else 
				{
					// Double-sided without PegMidtextureFlag
					surfaceHeight = Math.Abs(side.Sector.CeilHeight - side.Other.Sector.CeilHeight) * scaleY;
				}
			}
			else
			{
				if(side.Line.IsFlagSet(General.Map.Config.PegMidtextureFlag))
				{
					// Single-sided with PegMidtextureFlag set
					// Absolute value is used because ceiling height of vavoom-type 3d floors 
					// is lower than floor height
					surfaceHeight = (Math.Abs(side.Sector.CeilHeight - side.Sector.FloorHeight)) * scaleY;
				}
				else
				{
					// Single-sided without PegMidtextureFlag
					return offset;
				}
			}

			return Math.Round((fromNormalized ? offset + surfaceHeight : offset - surfaceHeight), General.Map.FormatInterface.VertexDecimals);
		}

		//mxd. This converts offsetY from/to "normalized" offset for given lower wall
		public static double GetSidedefBottomOffsetY(Sidedef side, double offset, double scaleY, bool fromNormalized) 
		{
			double surfaceHeight;

			// Make sure the offset doesn't go in the wrong direction
			scaleY = Math.Abs(scaleY);

			if (side.Line.IsFlagSet(General.Map.Config.LowerUnpeggedFlag)) 
			{
				if(side.Other == null || side.Other.Sector == null || !side.Sector.HasSkyCeiling ||
					!side.Other.Sector.HasSkyCeiling)
					return offset;

				//normalize offset the way Doom does it when front and back sector's ceiling is sky
				surfaceHeight = (side.Sector.CeilHeight - side.Other.Sector.CeilHeight) * scaleY;
			} 
			else 
			{
				//normalize offset
				surfaceHeight = (side.Sector.CeilHeight - side.Other.Sector.FloorHeight) * scaleY;
			}

			return Math.Round((fromNormalized ? offset + surfaceHeight : offset - surfaceHeight), General.Map.FormatInterface.VertexDecimals);
		}
		
		#endregion
		
		#region ================== Tags and Actions
		
		/// <summary>
		/// This removes all tags on the marked geometry.
		/// </summary>
		public static void RemoveMarkedTags()
		{
			General.Map.Map.ForAllTags<object>(RemoveTagHandler, true, null);
		}
		
		// This removes tags
		private static void RemoveTagHandler(MapElement element, bool actionargument, UniversalType type, ref int value, object obj)
		{
			value = 0;
		}
		
		/// <summary>
		/// This renumbers all tags on the marked geometry.
		/// </summary>
		public static void RenumberMarkedTags()
		{
			Dictionary<int, int> tagsmap = new Dictionary<int, int>();
			
			// Collect the tag numbers used in the marked geometry
			General.Map.Map.ForAllTags(CollectTagNumbersHandler, true, tagsmap);
			
			// Get new tags that are unique within unmarked geometry
			List<int> newtags = General.Map.Map.GetMultipleNewTags(tagsmap.Count, false);
			
			// Map the old tags with the new tags
			int index = 0;
			List<int> oldkeys = new List<int>(tagsmap.Keys);
			foreach(int ot in oldkeys) tagsmap[ot] = newtags[index++];
			
			// Now renumber the old tags with the new ones
			General.Map.Map.ForAllTags(RenumberTagsHandler, true, tagsmap);
		}
		
		// This collects tags in a dictionary
		private static void CollectTagNumbersHandler(MapElement element, bool actionargument, UniversalType type, ref int value, Dictionary<int, int> tagsmap)
		{
			if(value != 0)
				tagsmap[value] = value;
		}

		// This remaps tags from a dictionary
		private static void RenumberTagsHandler(MapElement element, bool actionargument, UniversalType type, ref int value, Dictionary<int, int> tagsmap)
		{
			if(value != 0)
				value = tagsmap[value];
		}
		
		/// <summary>
		/// This removes all actions on the marked geometry.
		/// </summary>
		public static void RemoveMarkedActions()
		{
			// Remove actions from things
			foreach(Thing t in General.Map.Map.Things)
			{
				if(t.Marked)
				{
					t.Action = 0;
					for(int i = 0; i < t.Args.Length; i++) t.Args[i] = 0;
				}
			}
			
			// Remove actions from linedefs
			foreach(Linedef l in General.Map.Map.Linedefs)
			{
				if(l.Marked)
				{
					l.Action = 0;
					for(int i = 0; i < l.Args.Length; i++) l.Args[i] = 0;
				}
			}
		}
		
		#endregion

		#region ================== Things (mxd)

		public static bool TryAlignThingToLine(Thing t, Linedef l) 
		{
			if(l.Back == null) 
			{
				if(CanAlignThingTo(t, l.Front.Sector))
				{
					AlignThingToLine(t, l, true);
					return true;
				}
				return false;
			}

			if(l.Front == null ) 
			{
				if(CanAlignThingTo(t, l.Back.Sector)) 
				{
					AlignThingToLine(t, l, false);
					return true;
				}
				return false;
			}

			double side = l.SideOfLine(t.Position);

			//already on line
			if(side == 0) 
			{ 
				t.Rotate(General.ClampAngle(180 + l.AngleDeg));
				return true;
			}

			//thing is on front side of the line
			if(side < 0) 
			{ 
				//got any walls to align to?
				if((l.Front.LongMiddleTexture != MapSet.EmptyLongName && CanAlignThingTo(t, l.Front.Sector)) 
					|| CanAlignThingTo(t, l.Front.Sector, l.Back.Sector)) 
				{
					AlignThingToLine(t, l, true);
					return true;
				}

				return false;
			}

			//thing is on back side of the line
			//got any walls to align to?
			if((l.Back.LongMiddleTexture != MapSet.EmptyLongName && CanAlignThingTo(t, l.Back.Sector)) 
				|| CanAlignThingTo(t, l.Back.Sector, l.Front.Sector)) 
			{
				AlignThingToLine(t, l, false);
				return true;
			}

			return false;
		}

		// Checks if there's a wall at appropriate height to align thing to
		private static bool CanAlignThingTo(Thing t, Sector front, Sector back) 
		{
			ThingTypeInfo ti = General.Map.Data.GetThingInfo(t.Type);
			int absz = GetThingAbsoluteZ(t, ti);
			int height = ti.Height == 0 ? 1 : (int)ti.Height;
			Rectangle thing =  new Rectangle(0, t.IsFlipped ? absz - height : absz, 1, height);

			if(front.FloorHeight < back.FloorHeight) 
			{
				Rectangle lower = new Rectangle(0, front.FloorHeight, 1, back.FloorHeight - front.FloorHeight);
				if(thing.IntersectsWith(lower)) return true;
			}

			if(front.CeilHeight > back.CeilHeight) 
			{
				Rectangle upper = new Rectangle(0, back.CeilHeight, 1, front.CeilHeight - back.CeilHeight);
				if(thing.IntersectsWith(upper)) return true;
			}

			return false;
		}

		// Checks if there's a wall at appropriate height to align thing to
		private static bool CanAlignThingTo(Thing t, Sector sector) 
		{
			ThingTypeInfo ti = General.Map.Data.GetThingInfo(t.Type);
			int absz = GetThingAbsoluteZ(t, ti);
			Rectangle thing = new Rectangle(0, absz, 1, ti.Height == 0 ? 1 : (int)ti.Height);

			Rectangle middle = new Rectangle(0, sector.FloorHeight, 1, sector.CeilHeight - sector.FloorHeight);
			return thing.IntersectsWith(middle);
		}

		private static void AlignThingToLine(Thing t, Linedef l, bool front) 
		{
			//get aligned position
			Vector2D pos = l.NearestOnLine(t.Position);
			Sector initialSector = t.Sector;

			//add a small offset so we don't end up moving thing into void
			if(front)
				t.Move(new Vector2D(pos.x - Math.Cos(l.Angle), pos.y - Math.Sin(l.Angle)));
			else
				t.Move(new Vector2D(pos.x + Math.Cos(l.Angle), pos.y + Math.Sin(l.Angle)));

			//apply new settings
			t.SnapToAccuracy();
			t.DetermineSector();
			t.Rotate(General.ClampAngle(front ? 180 + l.AngleDeg : l.AngleDeg));

			//keep thing height constant
			if(initialSector != t.Sector && General.Map.FormatInterface.HasThingHeight) 
			{
				ThingTypeInfo ti = General.Map.Data.GetThingInfo(t.Type);
				if(ti.AbsoluteZ || t.AbsoluteZ) return;

				if(t.IsFlipped && initialSector.CeilHeight != t.Sector.CeilHeight) 
				{
					t.Move(t.Position.x, t.Position.y, t.Position.z - (initialSector.CeilHeight - t.Sector.CeilHeight));
					return;
				}

				if(initialSector.FloorHeight != t.Sector.FloorHeight)
					t.Move(t.Position.x, t.Position.y, t.Position.z + (initialSector.FloorHeight - t.Sector.FloorHeight));
			}
		}

		public static int GetThingAbsoluteZ(Thing t, ThingTypeInfo ti)
		{
			// Determine z info
			if(ti.AbsoluteZ || t.AbsoluteZ) return (int)t.Position.z;

			if(t.Sector != null) 
			{
				// Hangs from ceiling? / is flipped?
				if(t.IsFlipped) return (int)(t.Sector.CeilHeight - t.Position.z - ti.Height);
				
				return (int)(t.Sector.FloorHeight + t.Position.z);
			}
			return (int)t.Position.z;
		}

		#endregion

		#region ================== Sectors (mxd)

		public static void SplitOuterSectors(IEnumerable<Linedef> drawnlines)
		{
			Dictionary<Sector, HashSet<Sidedef>> sectorsidesref = new Dictionary<Sector, HashSet<Sidedef>>();
			HashSet<Sidedef> drawnsides = new HashSet<Sidedef>();

			// Create drawn lines per sector collection
			foreach(Linedef l in drawnlines)
			{
				if(l.Front != null && (l.Front.Sector != null && !SectorWasInvalid(l.Front.Sector)))
				{
					// Add only multipart sectors
					if(l.Front.Sector.Triangles.IslandVertices.Count > 1)
					{
						if(!sectorsidesref.ContainsKey(l.Front.Sector)) sectorsidesref[l.Front.Sector] = new HashSet<Sidedef>();
						sectorsidesref[l.Front.Sector].Add(l.Front);
					}
					drawnsides.Add(l.Front);
				}

				if(l.Back != null && (l.Back.Sector != null && !SectorWasInvalid(l.Back.Sector)))
				{
					// Add only multipart sectors
					if(l.Back.Sector.Triangles.IslandVertices.Count > 1)
					{
						if(!sectorsidesref.ContainsKey(l.Back.Sector)) sectorsidesref[l.Back.Sector] = new HashSet<Sidedef>();
						sectorsidesref[l.Back.Sector].Add(l.Back);
					}
					drawnsides.Add(l.Back);
				}
			}

			// Split sectors
			foreach(KeyValuePair<Sector, HashSet<Sidedef>> group in sectorsidesref)
			{
				// Sector has all sides selected?
				if(group.Key.Sidedefs.Count == group.Value.Count)
				{
					group.Key.Marked = true; // Sometimes those are not marked...
					continue;
				}

				// Process all sides
				foreach(Sidedef side in group.Value)
				{
					// Sector was already split?
					if(side.Sector != group.Key) continue;

					// Find drawing interior
					List<LinedefSide> linedefsides = FindPotentialSectorAt(side.Line, side.IsFront);

					// Number of potential sides fewer than the sector has?
					if(linedefsides != null && linedefsides.Count > 0 && linedefsides.Count < group.Key.Sidedefs.Count)
					{
						// Collect sidedefs from new sector shape...
						HashSet<Sidedef> newsectorsides = new HashSet<Sidedef>();
						foreach(LinedefSide ls in linedefsides)
						{
							Sidedef s = (ls.Front ? ls.Line.Front : ls.Line.Back);
							if(s != null) newsectorsides.Add(s);
						}

						// Make new sector only if one of the remaining sector sides was also drawn...
						foreach(Sidedef s in group.Key.Sidedefs)
						{
							if(newsectorsides.Contains(s)) continue;
							if(drawnsides.Contains(s))
							{
								Sector newsector = MakeSector(linedefsides, null, false);
								if(newsector != null)
								{
									newsector.UpdateCache();
									group.Key.UpdateCache();
								}

								// Existing sector may've become invalid
								SectorWasInvalid(group.Key);

								break;
							}
						}
					}
				}
			}
		}

		private static bool SectorWasInvalid(Sector s)
		{
			if(s.Sidedefs == null || s.Sidedefs.Count < 3 || s.FlatVertices.Length < 3)
			{
				// Collect changed lines
				HashSet<Linedef> changedlines = new HashSet<Linedef>();
				if(s.Sidedefs != null)
				{
					foreach(Sidedef side in s.Sidedefs) changedlines.Add(side.Line);
				}

				// Delete sector
				s.Dispose();

				// Correct lines
				foreach(Linedef l in changedlines)
				{
					l.ApplySidedFlags();
					if(l.Front == null)
					{
						l.FlipVertices();
						l.FlipSidedefs();
					}
				}

				return true;
			}

			return false;
		}

		#endregion

		#region ================== Linedefs (mxd)

		/// <summary>Flips sector linedefs so they all face either inward or outward.</summary>
		public static void FlipSectorLinedefs(ICollection<Sector> sectors, bool selectedlinesonly) 
		{
			HashSet<Linedef> processed = new HashSet<Linedef>();
			
			foreach(Sector s in sectors) 
			{
				List<Linedef> frontlines = new List<Linedef>();
				List<Linedef> backlines = new List<Linedef>();
				int unselectedfrontlines = 0;
				int unselectedbacklines = 0;

				//sort lines
				foreach(Sidedef side in s.Sidedefs) 
				{
					if(processed.Contains(side.Line)) continue;
					if(selectedlinesonly && !side.Line.Selected)
					{
						if(side == side.Line.Front) unselectedfrontlines++;
						else unselectedbacklines++;
						continue;
					}
					
					if(side == side.Line.Front) 
						frontlines.Add(side.Line);
					else
						backlines.Add(side.Line);

					processed.Add(side.Line);
				}

				//flip lines
				if(frontlines.Count == 0 || (frontlines.Count + unselectedfrontlines > backlines.Count + unselectedbacklines && backlines.Count > 0)) 
				{
					foreach(Linedef l in backlines) 
					{
						l.FlipVertices();
						l.FlipSidedefs();
					}
				} 
				else 
				{
					foreach(Linedef l in frontlines) 
					{
						// Skip single-sided lines with only front side
						if(l.Back != null)
						{
							l.FlipVertices();
							l.FlipSidedefs();
						}
					}
				}
			}
		}

		#endregion

		#region ================== Sidedefs (mxd)

		/// <summary>Updates the 'lightfog' UDMF flag to display sidedef brightness on fogged walls. Returns 1 if flag was added, -1 if it was removed, 0 if flag wasn't changed</summary>
		public static int UpdateLightFogFlag(Sidedef side) 
		{
			//Side requires the flag?
			if(side.Sector == null) return 0;
			if(!side.Fields.ContainsKey("light")) 
			{
				//Unset the flag
				if(side.IsFlagSet("lightfog")) 
				{
					side.SetFlag("lightfog", false);
					return -1;
				}
				return 0;
			}

			//Update the flag
			if(General.Map.Data.MapInfo.HasFadeColor ||
			   (General.Map.Data.MapInfo.HasOutsideFogColor && side.Sector.HasSkyCeiling) ||
			   side.Sector.Fields.ContainsKey("fadecolor")) 
			{
				//Set the flag
				if(!side.IsFlagSet("lightfog")) 
				{
					side.SetFlag("lightfog", true);
					return 1;
				}
			} 
			else 
			{
				//Unset the flag
				if(side.IsFlagSet("lightfog")) 
				{
					side.SetFlag("lightfog", false);
					return -1;
				}
			}

			return 0;
		}

		#endregion

		#region ================== Misc Exported Functions

		/// <summary>
		/// This performs a Hermite spline interpolation and returns the result position.
		/// Where u (0 - 1) is the wanted position on the curve between p1 (using tangent t1) and p2 (using tangent t2).
		/// </summary>
		public static Vector2D HermiteSpline(Vector2D p1, Vector2D t1, Vector2D p2, Vector2D t2, float u)
		{
			return RenderDevice.V2D(Vector2f.Hermite(RenderDevice.V2(p1), RenderDevice.V2(t1), RenderDevice.V2(p2), RenderDevice.V2(t2), u));
		}

		/// <summary>
		/// This performs a Hermite spline interpolation and returns the result position.
		/// Where u (0 - 1) is the wanted position on the curve between p1 (using tangent t1) and p2 (using tangent t2).
		/// </summary>
		public static Vector3D HermiteSpline(Vector3D p1, Vector3D t1, Vector3D p2, Vector3D t2, float u)
		{
			return RenderDevice.V3D(Vector3f.Hermite(RenderDevice.V3(p1), RenderDevice.V3(t1), RenderDevice.V3(p2), RenderDevice.V3(t2), u));
		}

		//mxd
		public static int GetDropDownWidth(ComboBox cb) 
		{
			int maxwidth = 0;
			foreach(var obj in cb.Items)
			{
				int temp = TextRenderer.MeasureText(obj.ToString(), cb.Font).Width;
				if(temp > maxwidth) maxwidth = temp;
			}
			return maxwidth > 0 ? maxwidth + 6 : 1;
		}

		//mxd
		public static PixelColor GetSectorFadeColor(Sector s)
		{
			if(s.Fields.ContainsKey("fadecolor")) return PixelColor.FromInt(s.Fields.GetValue("fadecolor", 0));
			if(General.Map.Data.MapInfo.HasOutsideFogColor && s.HasSkyCeiling)
				return PixelColor.FromColor(General.Map.Data.MapInfo.OutsideFogColor.ToColor());

			return PixelColor.FromColor(General.Map.Data.MapInfo.HasFadeColor ? General.Map.Data.MapInfo.FadeColor.ToColor() : Color.Black);
		}

		#endregion
	}
}
