Added 3 map geometry dragging modes (used when applying Drag Vertices/Linedefs/Sectors modes and Edit Selection mode):

- "Merge Dragged Vertices Only". Only vertex-line intersections will be processed (DB2 mode).
- "Merge Dragged Geometry". Geometry merging will be performed.
- "Replace with Dragged Geometry". Dragged geometry will replace underlaying geometry.
You can switch between these using 3 new actions, top toolbar buttons and Edit menu buttons.
Changed: activating the same 2D mode repeatedly now toggles View modes.
Renamed "Merge Geometry" action/menu item to "Snap to Geometry".
More fixes to vertex/linedef/sector dragging logic.
Updated ZDoom_DECORATE.cfg.

Build/Scripting/ZDoom_DECORATE.cfg

@@ -82,21 +82,21 @@ keywords
 	A_ClearLastHeard = "A_ClearLastHeard";
 	A_ClearSoundTarget = "A_ClearSoundTarget";
 	A_ClearTarget = "A_ClearTarget";
-	A_DamageChildren = "A_DamageChildren(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_DamageChildren = "A_DamageChildren(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_DamageMaster = "A_DamageMaster(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_DamageMaster = "A_DamageMaster(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_DamageSelf = "A_DamageSelf(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_DamageSelf = "A_DamageSelf(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_DamageSiblings = "A_DamageSiblings(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_DamageSiblings = "A_DamageSiblings(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_DamageTarget = "A_DamageTarget(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_DamageTarget = "A_DamageTarget(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_DamageTracer = "A_DamageTracer(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_DamageTracer = "A_DamageTracer(int amount[, str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]]])\namount: amount of damage to inflict. Use a negative value to heal.\ndamagetype: the type of damage to inflict.\nflags: DMSS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
 	A_Die = "A_Die[(str damagetype = \"none\")]";
 	A_FaceTarget = "A_FaceTarget[(float angle = 0.0[, float pitch = 270.0])]\nA_FaceTarget([float max_turn = 0.0[, float max_pitch = 270.0[, float ang_offset = 0.0[, float pitch_offset = 0.0[, int flags = 0[, float z_add = 0.0]]]]]])";
 	A_FaceMaster = "A_FaceMaster[(float angle = 0.0[, float pitch = 270.0])]\nA_FaceMaster([float max_turn = 0.0[, float max_pitch = 270.0[, float ang_offset = 0.0[, float pitch_offset = 0.0[, int flags = 0[, float z_add = 0.0]]]]]])";
 	A_FastChase = "A_FastChase";
-	A_KillChildren = "A_KillChildren[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\[, str species = \"None\]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_KillChildren = "A_KillChildren[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_KillMaster = "A_KillMaster[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_KillMaster = "A_KillMaster[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_KillSiblings = "A_KillSiblings[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_KillSiblings = "A_KillSiblings[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_KillTarget = "A_KillTarget[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_KillTarget = "A_KillTarget[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
-	A_KillTracer = "A_KillTracer[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
+	A_KillTracer = "A_KillTracer[(str damagetype = \"None\"[, int flags = 0[, str filter = \"None\"[, str species = \"None\"[, int src = AAPTR_DEFAULT[, int inflictor = AAPTR_DEFAULT]]]]])]\ndamagetype: if the actor dies, the actor will enter a death state based on damagetype if present (or pain state if using NODAMAGE).\nflags: KILS flags.\nfilter: the actor class to damage.\nspecies: the actor species to damage.";
 	A_Look = "A_Look";
 	A_Look2 = "A_Look2";
 	A_LookEx = "A_LookEx(int flags, float minseedist, float maxseedist, float maxheardist, float fov, state seestate)";
@@ -433,6 +433,7 @@ keywords
 	GetSpawnHealth = "int GetSpawnHealth()";
 	GetZAt = "float GetZAt([float x = 0.0[, float y = 0.0[, float angle = 0.0[, int flags = 0[, int pick_pointer = AAPTR_TARGET]]]]])";
 	GetGibHealth = "int GetGibHealth()";
+	GetCrouchFactor = "float GetCrouchFactor(int ptr = AAPTR_PLAYER1)";
 }
 
 properties
@@ -744,7 +745,14 @@ constants
 	AAPTR_TARGET;
 	AAPTR_MASTER;
 	AAPTR_TRACER;
-	AAPTR_PLAYER;
+	AAPTR_PLAYER1;
+	AAPTR_PLAYER2;
+	AAPTR_PLAYER3;
+	AAPTR_PLAYER4;
+	AAPTR_PLAYER5;
+	AAPTR_PLAYER6;
+	AAPTR_PLAYER7;
+	AAPTR_PLAYER8;
 	AAPTR_PLAYER_GETTARGET;
 	AAPTR_PLAYER_GETCONVERSATION;
 //A_SpawnItemEx flags

Source/Core/Builder.csproj

@@ -888,6 +888,7 @@
     <Compile Include="GZBuilder\Data\SharpCompressHelper.cs" />
     <Compile Include="GZBuilder\Data\SkyboxInfo.cs" />
     <Compile Include="GZBuilder\Data\ThingCopyData.cs" />
+    <Compile Include="Map\MergeGeometryMode.cs" />
     <Compile Include="Map\SectorBuilder.cs" />
     <Compile Include="Rendering\VisualVertexHandle.cs" />
     <Compile Include="Geometry\Line3D.cs" />
@@ -1168,6 +1169,9 @@
     <None Include="Resources\MixedThings.png" />
     <None Include="Resources\LinedefColorPresets.png" />
     <EmbeddedResource Include="Resources\MissingSky3D.png" />
+    <None Include="Resources\MergeGeo.png" />
+    <None Include="Resources\MergeGeoClassic.png" />
+    <None Include="Resources\MergeGeoRemoveLines.png" />
     <Content Include="Resources\Model.png" />
     <None Include="Resources\ModelDisabled.png" />
     <None Include="Resources\ModelFiltered.png" />

Source/Core/Config/ProgramConfiguration.cs

@@ -91,6 +91,7 @@ namespace CodeImp.DoomBuilder.Config
 		private bool locatetexturegroup; //mxd
 		private bool keeptexturefilterfocused; //mxd
 		private SplitLineBehavior splitlinebehavior; //mxd
+		private MergeGeometryMode mergegeomode; //mxd
 		private bool usehighlight; //mxd
 
 		//mxd. Script editor settings
@@ -204,6 +205,7 @@ namespace CodeImp.DoomBuilder.Config
 		public bool LocateTextureGroup { get { return locatetexturegroup; } internal set { locatetexturegroup = value; } } //mxd
 		public bool KeepTextureFilterFocused { get { return keeptexturefilterfocused; } internal set { keeptexturefilterfocused = value; } } //mxd
 		public SplitLineBehavior SplitLineBehavior { get { return splitlinebehavior; } set { splitlinebehavior = value; } } //mxd
+		public MergeGeometryMode MergeGeometryMode { get { return mergegeomode; } internal set { mergegeomode = value; } } //mxd
 		
 		//mxd. Highlight mode
 		public bool UseHighlight
@@ -349,7 +351,8 @@ namespace CodeImp.DoomBuilder.Config
 				showtexturesizes = cfg.ReadSetting("showtexturesizes", true);
 				locatetexturegroup = cfg.ReadSetting("locatetexturegroup", true); //mxd
 				keeptexturefilterfocused = cfg.ReadSetting("keeptexturefilterfocused", true); //mxd
-				splitlinebehavior = (SplitLineBehavior)General.Clamp(cfg.ReadSetting("splitlinebehavior", 0), 0, 3); //mxd
+				splitlinebehavior = (SplitLineBehavior)General.Clamp(cfg.ReadSetting("splitlinebehavior", 0), 0, Enum.GetValues(typeof(SplitLineBehavior)).Length - 1); //mxd
+				mergegeomode = (MergeGeometryMode)General.Clamp(cfg.ReadSetting("mergegeometrymode", (int)MergeGeometryMode.REPLACE), 0, Enum.GetValues(typeof(MergeGeometryMode)).Length - 1); //mxd
 				usehighlight = cfg.ReadSetting("usehighlight", true); //mxd
 
 				//mxd. Script editor
@@ -466,6 +469,7 @@ namespace CodeImp.DoomBuilder.Config
 			cfg.WriteSetting("locatetexturegroup", locatetexturegroup); //mxd
 			cfg.WriteSetting("keeptexturefilterfocused", keeptexturefilterfocused); //mxd
 			cfg.WriteSetting("splitlinebehavior", (int)splitlinebehavior); //mxd
+			cfg.WriteSetting("mergegeometrymode", (int)mergegeomode); //mxd
 			cfg.WriteSetting("usehighlight", usehighlight); //mxd
 
 			//mxd. Script editor

Source/Core/Controls/DebugConsole.cs

@@ -173,7 +173,10 @@ namespace CodeImp.DoomBuilder
 			counter += incrementby;
 		}
 
+		public static void ResetCounter() { ResetCounter(string.Empty); }
 		public static void ResetCounter(string message)
+		{
+			if(!string.IsNullOrEmpty(message))
 			{
 				if(message.Contains("%"))
 					message = message.Replace("%", counter.ToString());
@@ -181,6 +184,7 @@ namespace CodeImp.DoomBuilder
 					message = message.TrimEnd() + ": " + counter;
 
 				WriteLine(DebugMessageType.SPECIAL, message);
+			}
 
 			counter = 0;
 		}

Source/Core/Editing/ClassicMode.cs

@@ -633,7 +633,7 @@ namespace CodeImp.DoomBuilder.Editing
 		}
 
 		// This sets the view mode
-		private static void SetViewMode(ViewMode mode)
+		internal static void SetViewMode(ViewMode mode)
 		{
 			General.Map.CRenderer2D.SetViewMode(mode);
 			General.MainWindow.UpdateInterface();

Source/Core/Editing/EditModeInfo.cs

@@ -17,10 +17,13 @@
 #region ================== Namespaces
 
 using System;
+using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
+using System.Linq;
 using CodeImp.DoomBuilder.Actions;
 using CodeImp.DoomBuilder.Plugins;
+using CodeImp.DoomBuilder.Rendering;
 using CodeImp.DoomBuilder.VisualModes;
 
 #endregion
@@ -160,6 +163,15 @@ namespace CodeImp.DoomBuilder.Editing
 					// Switch back to last classic mode
 					General.Editing.ChangeMode(General.Editing.PreviousClassicMode.Name);
 				}
+				//mxd. The same mode? Switch view modes instead
+				else if(General.Editing.Mode is ClassicMode && General.Editing.Mode.GetType().FullName == type.FullName)
+				{
+					List<ViewMode> vmodes = new List<ViewMode>(Enum.GetValues(typeof(ViewMode)).Cast<ViewMode>());
+					int curmode = vmodes.IndexOf(General.Map.Renderer2D.ViewMode);
+					curmode = (curmode == vmodes.Count - 1 ? 0 : ++curmode);
+
+					ClassicMode.SetViewMode(vmodes[curmode]);
+				}
 				else
 				{
 					// Create instance

Source/Core/Geometry/Tools.cs

@@ -1260,8 +1260,8 @@ namespace CodeImp.DoomBuilder.Geometry
 				// self intersections for which splits were made above.
 				map.Update(true, false);
 				map.BeginAddRemove();
-				MapSet.SplitLinesByVertices(newlines, intersectverts, MapSet.STITCH_DISTANCE, null, false);
+				MapSet.SplitLinesByVertices(newlines, intersectverts, MapSet.STITCH_DISTANCE, null);
-				MapSet.SplitLinesByVertices(newlines, mergeverts, MapSet.STITCH_DISTANCE, null, false);
+				MapSet.SplitLinesByVertices(newlines, mergeverts, MapSet.STITCH_DISTANCE, null);
 				map.EndAddRemove();
 				
 				/***************************************************\
@@ -1328,7 +1328,7 @@ namespace CodeImp.DoomBuilder.Geometry
 				// 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.
-				map.StitchGeometry(false);
+				map.StitchGeometry();
 				map.Update(true, false);
 
 				// Find our new lines again, because they have been merged with the other geometry

Source/Core/Map/MapSet.cs

@@ -1988,9 +1988,9 @@ namespace CodeImp.DoomBuilder.Map
 		}
 
 		/// <summary>This filters lines by a rectangular area.</summary>
-		public static List<Linedef> FilterByArea(ICollection<Linedef> lines, ref RectangleF area)
+		public static HashSet<Linedef> FilterByArea(ICollection<Linedef> lines, ref RectangleF area)
 		{
-			List<Linedef> newlines = new List<Linedef>(lines.Count);
+			HashSet<Linedef> newlines = new HashSet<Linedef>();
 			
 			// Go for all lines
 			foreach(Linedef l in lines)
@@ -2045,18 +2045,18 @@ namespace CodeImp.DoomBuilder.Map
 		/// <summary>
 		/// Stitches marked geometry with non-marked geometry. Returns false when the operation failed.
 		/// </summary>
-		public bool StitchGeometry() { return StitchGeometry(false); } //mxd. Compatibility
+		public bool StitchGeometry() { return StitchGeometry(MergeGeometryMode.CLASSIC); } //mxd. Compatibility
-		public bool StitchGeometry(bool correctsectorrefs)
+		public bool StitchGeometry(MergeGeometryMode mergemode)
 		{
 			// Find vertices
-			ICollection<Vertex> movingverts = General.Map.Map.GetMarkedVertices(true);
+			HashSet<Vertex> movingverts = new HashSet<Vertex>(General.Map.Map.GetMarkedVertices(true));
-			ICollection<Vertex> fixedverts = General.Map.Map.GetMarkedVertices(false);
+			HashSet<Vertex> fixedverts = new HashSet<Vertex>(General.Map.Map.GetMarkedVertices(false));
 			
 			// Find lines that moved during the drag
-			List<Linedef> movinglines = LinedefsFromMarkedVertices(false, true, true);
+			HashSet<Linedef> movinglines = new HashSet<Linedef>(LinedefsFromMarkedVertices(false, true, true));
 			
 			// Find all non-moving lines
-			List<Linedef> fixedlines = LinedefsFromMarkedVertices(true, false, false);
+			HashSet<Linedef> fixedlines = new HashSet<Linedef>(LinedefsFromMarkedVertices(true, false, false));
 			
 			// Determine area in which we are editing
 			RectangleF editarea = CreateArea(movinglines);
@@ -2075,16 +2075,16 @@ namespace CodeImp.DoomBuilder.Map
 			
 			// Split moving lines with unselected vertices
 			ICollection<Vertex> nearbyfixedverts = FilterByArea(fixedverts, ref editarea);
-			if(!SplitLinesByVertices(movinglines, nearbyfixedverts, STITCH_DISTANCE, movinglines, correctsectorrefs))
+			if(!SplitLinesByVertices(movinglines, nearbyfixedverts, STITCH_DISTANCE, movinglines, mergemode))
 				return false;
 			
 			// Split non-moving lines with selected vertices
 			fixedlines = FilterByArea(fixedlines, ref editarea);
-			if(!SplitLinesByVertices(fixedlines, movingverts, STITCH_DISTANCE, movinglines, correctsectorrefs))
+			if(!SplitLinesByVertices(fixedlines, movingverts, STITCH_DISTANCE, movinglines, mergemode))
 				return false;
 
 			//mxd. Split moving lines with fixed lines
-			if(!SplitLinesByLines(fixedlines, movinglines, correctsectorrefs)) return false;
+			if(!SplitLinesByLines(fixedlines, movinglines, mergemode)) return false;
 			
 			// Remove looped linedefs
 			RemoveLoopedLinedefs(movinglines);
@@ -2092,10 +2092,49 @@ namespace CodeImp.DoomBuilder.Map
 			// Join overlapping lines
 			if(!JoinOverlappingLines(movinglines)) return false;
 
+			//mxd. Remove remaining new verts from dragged shape if possible
+			if(mergemode == MergeGeometryMode.REPLACE)
+			{
+				// Get lines, which belong to dragged sectors
+				HashSet<Sector> draggedsectors = GetSectorsFromLinedefs(movinglines);
+				HashSet<Linedef> sectorlines = new HashSet<Linedef>();
+				foreach(Sector s in draggedsectors)
+				{
+					foreach(Sidedef side in s.Sidedefs)
+						sectorlines.Add(side.Line);
+				}
+
+				HashSet<Vertex> tocheck = new HashSet<Vertex>();
+
+				foreach(Linedef l in sectorlines)
+				{
+					if(l.IsDisposed) continue;
+					if(!movingverts.Contains(l.Start)) tocheck.Add(l.Start);
+					if(!movingverts.Contains(l.End)) tocheck.Add(l.End);
+				}
+
+				// Remove verts, which are not part of initially dragged verts
+				foreach(Vertex v in tocheck)
+				{
+					if(!v.IsDisposed && v.Linedefs.Count == 2)
+					{
+						Linedef ld1 = General.GetByIndex(v.Linedefs, 0);
+						Linedef ld2 = General.GetByIndex(v.Linedefs, 1);
+
+						Vertex v2 = (ld2.Start == v) ? ld2.End : ld2.Start;
+						if(ld1.Start == v) ld1.SetStartVertex(v2); else ld1.SetEndVertex(v2);
+						ld2.Dispose();
+
+						// Trash vertex
+						v.Dispose();
+					}
+				}
+			}
+
 			EndAddRemove();
 
 			//mxd. Correct sector references
-			if(correctsectorrefs)
+			if(mergemode != MergeGeometryMode.CLASSIC)
 			{
 				// Linedefs cache needs to be up to date...
 				Update(true, false);
@@ -2104,6 +2143,11 @@ namespace CodeImp.DoomBuilder.Map
 				List<Linedef> changedlines = LinedefsFromMarkedVertices(false, true, true);
 				CorrectSectorReferences(changedlines, true);
 				CorrectOuterSides(new HashSet<Linedef>(changedlines));
+
+				// Mark only fully selected sectors
+				ClearMarkedSectors(false);
+				HashSet<Sector> changedsectors = GetSectorsFromLinedefs(changedlines);
+				foreach(Sector s in changedsectors) s.Marked = true;
 			}
 			
 			return true;
@@ -2112,6 +2156,9 @@ namespace CodeImp.DoomBuilder.Map
 		//mxd. Shameless SLADEMap::correctSectors ripoff... Corrects/builds sectors for all lines in [lines]
 		private static void CorrectSectorReferences(List<Linedef> lines, bool existing_only)
 		{
+			//DebugConsole.Clear();
+			//DebugConsole.WriteLine("CorrectSectorReferences for " + lines.Count + " lines");
+			
 			// Create a list of sidedefs to perform sector creation with
 			List<LinedefSide> edges = new List<LinedefSide>();
 			if(existing_only)
@@ -2151,15 +2198,9 @@ namespace CodeImp.DoomBuilder.Map
 			HashSet<Sector> affectedsectors = new HashSet<Sector>(General.Map.Map.GetSelectedSectors(true));
 			affectedsectors.UnionWith(General.Map.Map.GetUnselectedSectorsFromLinedefs(lines));
 
-			//mxd. Collect their lines
+			//mxd. Collect their sidedefs
-			HashSet<Linedef> sectorlines = new HashSet<Linedef>();
+			HashSet<Sidedef> sectorsides = new HashSet<Sidedef>();
-			foreach(Sector s in affectedsectors)
+			foreach(Sector s in affectedsectors) sectorsides.UnionWith(s.Sidedefs);
-			{
-				foreach(Sidedef side in s.Sidedefs)
-				{
-					if(side.Line != null) sectorlines.Add(side.Line);
-				}
-			}
 
 			// Build sectors
 			SectorBuilder builder = new SectorBuilder();
@@ -2168,6 +2209,7 @@ namespace CodeImp.DoomBuilder.Map
 			foreach(LinedefSide ls in edges)
 			{
 				// Skip if edge is ignored
+				//DebugConsole.WriteLine((ls.Ignore ? "Ignoring line " : "Processing line ") + ls.Line.Index);
 				if(ls.Ignore) continue;
 
 				// Run sector builder on current edge
@@ -2176,13 +2218,15 @@ namespace CodeImp.DoomBuilder.Map
 				// Find any subsequent edges that were part of the sector created
 				bool has_existing_lines = false;
 				bool has_existing_sides = false;
-				bool has_zero_sided_lines = false;
+				//bool has_zero_sided_lines = false;
-				bool has_sides_belonging_to_dragged_sectors = false; //mxd
+				bool has_dragged_sides = false; //mxd
 				List<LinedefSide> edges_in_sector = new List<LinedefSide>();
 				foreach(LinedefSide edge in builder.SectorEdges)
 				{
 					bool line_is_ours = false;
-					if(sectorlines.Contains(edge.Line)) has_sides_belonging_to_dragged_sectors = true; //mxd
+					bool side_exists = (edge.Front ? edge.Line.Front != null : edge.Line.Back != null); //mxd
+					if(side_exists && sectorsides.Contains(edge.Front ? edge.Line.Front : edge.Line.Back))
+						has_dragged_sides = true; //mxd
 
 					foreach(LinedefSide ls2 in edges)
 					{
@@ -2199,14 +2243,13 @@ namespace CodeImp.DoomBuilder.Map
 
 					if(line_is_ours)
 					{
-						if(edge.Line.Front == null && edge.Line.Back == null)
+						//if(edge.Line.Front == null && edge.Line.Back == null)
-							has_zero_sided_lines = true;
+							//has_zero_sided_lines = true;
 					}
 					else
 					{
 						has_existing_lines = true;
-						if(edge.Front ? edge.Line.Front != null : edge.Line.Back != null)
+						has_existing_sides |= side_exists; //mxd
-							has_existing_sides = true;
 					}
 				}
 
@@ -2217,7 +2260,8 @@ namespace CodeImp.DoomBuilder.Map
 				// in an enclosed void, and should not be drawn.
 				// However, if existing_only is false, the caller expects us to create
 				// new sides anyway; skip this check.
-				if(existing_only && has_existing_lines && !has_existing_sides && !has_sides_belonging_to_dragged_sectors) continue;
+				if(existing_only && has_existing_lines && !has_existing_sides && !has_dragged_sides)
+					continue;
 
 				// Ignore traced edges when trying to create any further sectors
 				foreach(LinedefSide ls3 in edges_in_sector) ls3.Ignore = true;
@@ -2331,7 +2375,7 @@ namespace CodeImp.DoomBuilder.Map
 			foreach(Sidedef side in newsides)
 			{
 				// Clear any unneeded textures
-				side.RemoveUnneededTextures(side.Other != null);
+				side.RemoveUnneededTextures(side.Other != null, false, true);
 
 				// Set middle texture if needed
 				if(side.MiddleRequired() && side.MiddleTexture == "-")
@@ -2627,8 +2671,8 @@ namespace CodeImp.DoomBuilder.Map
 				// Go for all the lines
 				foreach(Linedef l in lines)
 				{
-					// Check if referencing the same vertex twice
+					// Check if referencing the same vertex twice (mxd. Or if both verts are null)
-					if(l.Start == l.End)
+					if(l.Start == l.End || l.Start.Position == l.End.Position)
 					{
 						// Remove this line
 						while(lines.Remove(l));
@@ -2784,8 +2828,8 @@ namespace CodeImp.DoomBuilder.Map
 
 		/// <summary>This splits the given lines with the given vertices. All affected lines
 		/// will be added to changedlines. Returns false when the operation failed.</summary>
-		public static bool SplitLinesByVertices(ICollection<Linedef> lines, ICollection<Vertex> verts, float splitdist, ICollection<Linedef> changedlines) { return SplitLinesByVertices(lines, verts, splitdist, changedlines, false); }
+		public static bool SplitLinesByVertices(ICollection<Linedef> lines, ICollection<Vertex> verts, float splitdist, ICollection<Linedef> changedlines) { return SplitLinesByVertices(lines, verts, splitdist, changedlines, MergeGeometryMode.CLASSIC); }
-		public static bool SplitLinesByVertices(ICollection<Linedef> lines, ICollection<Vertex> verts, float splitdist, ICollection<Linedef> changedlines, bool removeinnerlines)
+		public static bool SplitLinesByVertices(ICollection<Linedef> lines, ICollection<Vertex> verts, float splitdist, ICollection<Linedef> changedlines, MergeGeometryMode mergemode)
 		{
 			if(verts.Count == 0 || lines.Count == 0) return true; //mxd
 			
@@ -2802,9 +2846,14 @@ namespace CodeImp.DoomBuilder.Map
 			BlockEntry[,] bmap = blockmap.Map;
 
 			//mxd
-			//HashSet<Vertex> splitverts = new HashSet<Vertex>();
+			HashSet<Vertex> splitverts = new HashSet<Vertex>();
-			//HashSet<Sector> changedsectors = (removeinnerlines ? General.Map.Map.GetSectorsFromLinedefs(changedlines) : new HashSet<Sector>());
+			HashSet<Sector> changedsectors = (mergemode == MergeGeometryMode.REPLACE ? General.Map.Map.GetSectorsFromLinedefs(changedlines) : new HashSet<Sector>());
-			//HashSet<Linedef> initialchanedlines = new HashSet<Linedef>(changedlines);
+			HashSet<Vertex> lineverts = new HashSet<Vertex>();
+			foreach(Linedef l in lines)
+			{
+				lineverts.Add(l.Start);
+				lineverts.Add(l.End);
+			}
 
 			for(int w = 0; w < bmWidth; w++) 
 			{
@@ -2836,7 +2885,7 @@ namespace CodeImp.DoomBuilder.Map
 									Linedef nl = l.Split(v);
 									if(nl == null) return false;
 									v.Marked = true; //mxd
-									//splitverts.Add(v); //mxd
+									splitverts.Add(v); //mxd
 
 									// Add the new line to the list
 									lines.Add(nl);
@@ -2860,7 +2909,7 @@ namespace CodeImp.DoomBuilder.Map
 			}
 
 			//mxd. Remove lines, which are inside affected sectors
-			/*if(removeinnerlines)
+			if(mergemode == MergeGeometryMode.REPLACE && changedsectors.Count > 0)
 			{
 				HashSet<Linedef> alllines = new HashSet<Linedef>(lines);
 				if(changedlines != null) alllines.UnionWith(changedlines);
@@ -2870,7 +2919,7 @@ namespace CodeImp.DoomBuilder.Map
 				foreach(Linedef l in alllines)
 				{
 					// Remove line when both it's start and end are inside a changed sector and neither side references it
-					if(l.Start != null && l.End != null && !initialchanedlines.Contains(l) &&
+					if(l.Start != null && l.End != null &&
 					  (l.Front == null || !changedsectors.Contains(l.Front.Sector)) &&
 					  (l.Back == null || !changedsectors.Contains(l.Back.Sector)))
 					{
@@ -2878,61 +2927,72 @@ namespace CodeImp.DoomBuilder.Map
 						{
 							if(s.Intersect(l.Start.Position) && s.Intersect(l.End.Position))
 							{
-								Vertex[] tocheck = new[] { l.Start, l.End };
+								Vertex[] tocheck = { l.Start, l.End };
-
+								while(lines.Remove(l));
-								// Remove from collections and dispose
+								if(changedlines != null) while(changedlines.Remove(l));
-								lines.Remove(l);
-								if(changedlines != null) changedlines.Remove(l);
 								l.Dispose();
 
 								foreach(Vertex v in tocheck)
 								{
-									// If the vertex only has 2 linedefs attached, then merge the linedefs
+									// If the newly created vertex only has 2 linedefs attached, then merge the linedefs
-									if(v.Linedefs.Count == 2)
+									if(!v.IsDisposed && v.Linedefs.Count == 2 && splitverts.Contains(v))
 									{
 										Linedef ld1 = General.GetByIndex(v.Linedefs, 0);
 										Linedef ld2 = General.GetByIndex(v.Linedefs, 1);
+										if(!ld1.Marked && !ld2.Marked)
+										{
 											Vertex v2 = (ld2.Start == v) ? ld2.End : ld2.Start;
 											if(ld1.Start == v) ld1.SetStartVertex(v2); else ld1.SetEndVertex(v2);
-										
+											while(lines.Remove(ld2));
-										// Remove from collections and dispose
+											if(changedlines != null) while(changedlines.Remove(ld2));
-										lines.Remove(ld2);
-										if(changedlines != null) changedlines.Remove(ld2);
 											ld2.Dispose();
 
 											// Trash vertex
 											v.Dispose();
 										}
 									}
+								}
 
 								break;
 							}
 						}
 					}
 				}
-			}*/
+			}
 			
 			return true;
 		}
 
 		/// <summary>Splits lines by lines. Adds new lines to the second collection. Returns false when the operation failed.</summary>
-		public static bool SplitLinesByLines(IList<Linedef> lines, IList<Linedef> changedlines, bool removeinnerlines) //mxd
+		public static bool SplitLinesByLines(HashSet<Linedef> lines, HashSet<Linedef> changedlines, MergeGeometryMode mergemode) //mxd
 		{
-			if(lines.Count == 0 || changedlines.Count == 0) return true;
+			if(lines.Count == 0 || changedlines.Count == 0 || mergemode == MergeGeometryMode.CLASSIC) return true;
 			
 			// Create blockmap
+			HashSet<Vertex> verts = new HashSet<Vertex>(); //mxd
+			foreach(Linedef l in lines)
+			{
+				verts.Add(l.Start);
+				verts.Add(l.End);
+			}
+			foreach(Linedef l in changedlines)
+			{
+				verts.Add(l.Start);
+				verts.Add(l.End);
+			}
+
 			RectangleF area = RectangleF.Union(CreateArea(lines), CreateArea(changedlines));
 			BlockMap<BlockEntry> blockmap = new BlockMap<BlockEntry>(area);
 			blockmap.AddLinedefsSet(lines);
 			blockmap.AddLinedefsSet(changedlines);
+			blockmap.AddVerticesSet(verts); //mxd
 			int bmWidth = blockmap.Size.Width;
 			int bmHeight = blockmap.Size.Height;
 			BlockEntry[,] bmap = blockmap.Map;
 
 			//mxd
 			HashSet<Vertex> splitverts = new HashSet<Vertex>();
-			HashSet<Sector> changedsectors = (removeinnerlines ? General.Map.Map.GetSectorsFromLinedefs(changedlines) : new HashSet<Sector>());
+			HashSet<Sector> changedsectors = (mergemode == MergeGeometryMode.REPLACE ? General.Map.Map.GetSectorsFromLinedefs(changedlines) : new HashSet<Sector>());
-			HashSet<Linedef> initialchanedlines = new HashSet<Linedef>(changedlines);
 
 			// Check for intersections
 			for(int w = 0; w < bmWidth; w++)
@@ -2960,8 +3020,25 @@ namespace CodeImp.DoomBuilder.Map
 							Vector2D intersection = Line2D.GetIntersectionPoint(new Line2D(l1), new Line2D(l2), true);
 							if(!float.IsNaN(intersection.x))
 							{
-								// Create split vertex
+								//mxd. Round to map format precision
-								Vertex splitvertex = General.Map.Map.CreateVertex(intersection);
+								intersection.x = (float)Math.Round(intersection.x, General.Map.FormatInterface.VertexDecimals);
+								intersection.y = (float)Math.Round(intersection.y, General.Map.FormatInterface.VertexDecimals);
+
+								//mxd. Do we already have a vertex here?
+								bool existingvert = false;
+								Vertex splitvertex = null;
+								foreach(Vertex v in block.Vertices)
+								{
+									if(v.Position == intersection)
+									{
+										splitvertex = v;
+										existingvert = true;
+										break;
+									}
+								}
+
+								//mxd. Create split vertex?
+								if(splitvertex == null) splitvertex = General.Map.Map.CreateVertex(intersection);
 								if(splitvertex == null) return false;
 
 								// Split both lines
@@ -2971,9 +3048,12 @@ namespace CodeImp.DoomBuilder.Map
 								Linedef nl2 = l2.Split(splitvertex);
 								if(nl2 == null) return false;
 
-								// Mark split vertex
+								// Mark split vertex?
+								if(!existingvert)
+								{
 									splitvertex.Marked = true;
 									splitverts.Add(splitvertex); //mxd
+								}
 
 								// Add to the second collection
 								changedlines.Add(nl1);
@@ -2989,7 +3069,7 @@ namespace CodeImp.DoomBuilder.Map
 			}
 
 			//mxd. Remove lines, which are inside affected sectors
-			if(removeinnerlines)
+			if(mergemode == MergeGeometryMode.REPLACE)
 			{
 				HashSet<Linedef> alllines = new HashSet<Linedef>(lines);
 				alllines.UnionWith(changedlines);
@@ -2999,21 +3079,26 @@ namespace CodeImp.DoomBuilder.Map
 				foreach(Linedef l in alllines)
 				{
 					// Remove line when both it's start and end are inside a changed sector and neither side references it
-					if(l.Start != null && l.End != null && !initialchanedlines.Contains(l) &&
+					if(l.Start != null && l.End != null)
-					  (l.Front == null || !changedsectors.Contains(l.Front.Sector)) &&
+					{
+						if(l.Front == null && l.Back == null)
+						{
+							l.Dispose();
+						}
+						else if((l.Front == null || !changedsectors.Contains(l.Front.Sector)) &&
 								(l.Back == null || !changedsectors.Contains(l.Back.Sector)))
 						{
 							foreach(Sector s in changedsectors)
 							{
 								if(s.Intersect(l.Start.Position) && s.Intersect(l.End.Position))
 								{
-								Vertex[] tocheck = new[] { l.Start, l.End };
+									Vertex[] tocheck = { l.Start, l.End };
 									l.Dispose();
 
 									foreach(Vertex v in tocheck)
 									{
-									// If the vertex only has 2 linedefs attached, then merge the linedefs
+										// If the newly created vertex only has 2 linedefs attached, then merge the linedefs
-									if(!v.IsDisposed && v.Linedefs.Count == 2)
+										if(!v.IsDisposed && v.Linedefs.Count == 2 && splitverts.Contains(v))
 										{
 											Linedef ld1 = General.GetByIndex(v.Linedefs, 0);
 											Linedef ld2 = General.GetByIndex(v.Linedefs, 1);
@@ -3032,6 +3117,7 @@ namespace CodeImp.DoomBuilder.Map
 						}
 					}
 				}
+			}
 
 			return true;
 		}

Source/Core/Map/MergeGeometryMode.cs

@@ -0,0 +1,9 @@
+namespace CodeImp.DoomBuilder.Map
+{
+	public enum MergeGeometryMode //mxd
+	{
+		CLASSIC,
+		MERGE,
+		REPLACE,
+	}
+}

Source/Core/Map/SectorBuilder.cs

@@ -64,19 +64,32 @@ namespace CodeImp.DoomBuilder.Map
 			for(int a = 0; a < 10000; a++)
 			{
 				// Trace outline
-				if(!TraceOutline(line, front)) break;
+				if(!TraceOutline(line, front))
+				{
+					//DebugConsole.WriteLine("TraceSector: find outmost outline failed");
+					break;
+				}
 
 				// Discard any vertices outside the traced outline
 				vertex_valid.RemoveWhere(PointOutsideOutline);
+				//DebugConsole.WriteLine("vertex_valid: " + vertex_valid.Count + " verts after RemoveWhere");
 
 				// If it is clockwise, we've found the outmost outline
-				if(o_clockwise) break;
+				if(o_clockwise)
+				{
+					//DebugConsole.WriteLine("TraceSector: found outmost outline");
+					break;
+				}
 
 				// Otherwise, find the next edge outside the outline
 				LinedefSide next = FindOuterEdge();
 
 				// If none was found, we're outside the map
-				if(next == null) return false;
+				if(next == null)
+				{
+					//DebugConsole.WriteLine("TraceSector aborted: no outer edge");
+					return false;
+				}
 
 				// Repeat with this edge
 				line = next.Line;
@@ -93,17 +106,25 @@ namespace CodeImp.DoomBuilder.Map
 				LinedefSide edge = FindInnerEdge();
 
 				// Check if we're done
-				if(edge == null) break;
+				if(edge == null)
+				{
+					//DebugConsole.WriteLine("No inner edge found (no edge)");
+					break;
+				}
 
 				// Trace outline from edge
-				if(!TraceOutline(edge.Line, edge.Front)) break;
+				if(!TraceOutline(edge.Line, edge.Front))
+				{
+					//DebugConsole.WriteLine("No inner edge found (TraceOutline failed)");
+					break;
+				}
 
 				// Discard any vertices outside the traced outline
 				vertex_valid.RemoveWhere(PointOutsideOutline);
+				//DebugConsole.WriteLine("vertex_valid: " + vertex_valid.Count + " verts after RemoveWhere");
 			}
 
 			//DebugConsole.WriteLine("FindInnerEdge: " + o_edges.Count + " lines");
-
 			return true;
 		}
 
@@ -119,6 +140,7 @@ namespace CodeImp.DoomBuilder.Map
 
 			// Init outline
 			o_edges.Clear();
+			o_bbox = RectangleF.Empty;
 			LinedefSide start = new LinedefSide(line, front);
 			o_edges.Add(start);
 			int edge_sum = 0;
@@ -144,12 +166,14 @@ namespace CodeImp.DoomBuilder.Map
 				// Get next edge. If no valid next edge was found, go back along the current line
 				LinedefSide edge_next = (NextEdge(edge, visited_lines) ?? new LinedefSide(edge.Line, !edge.Front));
 
-				//DebugConsole.WriteLine("Next line " + edge_next.Line.Index + (edge_next.Front ? " (front)" : " (back)"));
+				//DebugConsole.WriteLine("Next line for " + edge.Line.Index + (edge.Front ? " (front)" : " (back)") + ": " + edge_next.Line.Index + (edge_next.Front ? " (front)" : " (back)"));
 
 				// Discard edge vertices
 				vertex_valid.Remove(edge_next.Line.Start);
 				vertex_valid.Remove(edge_next.Line.End);
 
+				//DebugConsole.WriteLine("vertex_valid: " + vertex_valid.Count + " verts after Remove (in TraceOutline)");
+
 				// Check if we're back to the start
 				if(edge_next.Line == start.Line && edge_next.Front == start.Front)
 					break;
@@ -166,12 +190,15 @@ namespace CodeImp.DoomBuilder.Map
 					Math.Max(edge.Line.Start.Position.x, edge.Line.End.Position.x),  // right
 					Math.Max(edge.Line.Start.Position.y, edge.Line.End.Position.y)); // bottom
 
-				o_bbox = (o_bbox.IsEmpty ? l_bbox : RectangleF.Union(o_bbox, l_bbox));
+				//mxd. As it turned out, o_bbox.IsEmpty was not what we needed...
+				o_bbox = (o_bbox == RectangleF.Empty ? l_bbox : RectangleF.Union(o_bbox, l_bbox));
 			}
 
 			// Check if outline is clockwise
 			o_clockwise = (edge_sum < 0);
 
+			//DebugConsole.WriteLine("TraceOutline for line " + line.Index + " (" + (front ? "front":"back") + ") found " + o_edges.Count + " edges; o_clockwise=" + o_clockwise);
+
 			// Add outline edges to sector edge list
 			sector_edges.AddRange(o_edges);
 
@@ -230,6 +257,8 @@ namespace CodeImp.DoomBuilder.Map
 		/// <summary>Find the closest edge within the current outline (that isn't part of the current outline)</summary>
 		private LinedefSide FindInnerEdge()
 		{
+			//DebugConsole.WriteLine("FindInnerEdge: processing " + vertex_valid.Count + " verts");
+			
 			// Find rightmost non-discarded vertex
 			vertex_right = null;
 			foreach(Vertex v in vertex_valid)
@@ -247,7 +276,11 @@ namespace CodeImp.DoomBuilder.Map
 			}
 
 			// If no vertex was found, we're done
-			if(vertex_right == null) return null;
+			if(vertex_right == null)
+			{
+				//DebugConsole.WriteLine("FindInnerEdge: no vertex_right");
+				return null;
+			}
 
 			// Go through vertex's connected lines, to find
 			// the line with the smallest angle parallel with
@@ -280,6 +313,8 @@ namespace CodeImp.DoomBuilder.Map
 			{
 				// Discard vertex and try again
 				vertex_valid.Remove(vertex_right);
+				//DebugConsole.WriteLine("vertex_valid: " + vertex_valid.Count + " verts after Remove (in FindInnerEdge)");
+				
 				return FindInnerEdge();
 			}
 
@@ -384,11 +419,20 @@ namespace CodeImp.DoomBuilder.Map
 																	   //mxd. The meaning of 0.0 is also inverted!!!
 
 				// Return false if it is on the correct side
-				if(side > 0 && o_edges[nearest].Front) return false;
+				if(side > 0 && o_edges[nearest].Front)
-				if(side <= 0 && !o_edges[nearest].Front) return false;
+				{
+					//DebugConsole.WriteLine("Point " + point + " is within outline (infront of line) " + nearest);
+					return false;
+				}
+				if(side <= 0 && !o_edges[nearest].Front)
+				{
+					//DebugConsole.WriteLine("Point " + point + " is within outline (at the back of line) " + nearest);
+					return false;
+				}
 			}
 
 			// Not within the outline
+			//DebugConsole.WriteLine("Point " + point + " is outside outline");
 			return true;
 		}
 
@@ -491,7 +535,10 @@ namespace CodeImp.DoomBuilder.Map
 				if(sector_copy != null) sector_copy.CopyPropertiesTo(sector);
 			}
 
+			//DebugConsole.WriteLine(" ");
 			//DebugConsole.WriteLine("Creating sector " + sector.Index + " from " + sector_edges.Count + " lines");
+			//DebugConsole.WriteLine("*************************************************************");
+			//DebugConsole.WriteLine(" ");
 
 			// Set sides to new sector
 			foreach(LinedefSide edge in sector_edges)
@@ -501,14 +548,26 @@ namespace CodeImp.DoomBuilder.Map
 				{
 					if(target.Sector != sector)
 					{
+						bool targetwas2s = (target.Other != null);
 						target.SetSector(sector); //mxd. Reattach side
-						target.Marked = true; //mxd. Mark it
+
+						//mxd. Mark for texture adjustments if sidedness was changed.
+						//mxd. Also keep existing mark if the side was already marked.
+						target.Marked |= ((targetwas2s && target.Other == null) || (!targetwas2s && target.Other != null));
 					}
 				}
 				else
 				{
 					target = General.Map.Map.CreateSidedef(edge.Line, edge.Front, sector); //mxd. Create new side
-					target.Marked = true; //mxd. Mark it
+					target.Marked = true; //mxd. Mark it for texture adjustments
+					if(target.Other != null)
+					{
+						//mxd. Better than nothing
+						target.Other.CopyPropertiesTo(target);
+
+						//mxd. Other was singlesided. We'll need to adjust it's textures as well
+						target.Other.Marked = true; 
+					}
 				}
 			}
 		}

Source/Core/Map/Vertex.cs

@@ -330,7 +330,7 @@ namespace CodeImp.DoomBuilder.Map
 		public override string ToString()
 		{
 #if DEBUG
-			return "Vertex (" + pos + (marked ? "; marked" : "") + ")";
+			return "Vertex " + Index + " (" + pos + (marked ? "; marked" : "") + ")";
 #else
 			return "Vertex (" + pos + ")";
 #endif

Source/Core/Properties/Resources.Designer.cs

@@ -557,6 +557,20 @@ namespace CodeImp.DoomBuilder.Properties {
             }
         }
         
+        internal static System.Drawing.Bitmap MergeGeo {
+            get {
+                object obj = ResourceManager.GetObject("MergeGeo", resourceCulture);
+                return ((System.Drawing.Bitmap)(obj));
+            }
+        }
+        
+        internal static System.Drawing.Bitmap MergeGeoClassic {
+            get {
+                object obj = ResourceManager.GetObject("MergeGeoClassic", resourceCulture);
+                return ((System.Drawing.Bitmap)(obj));
+            }
+        }
+        
         internal static System.Drawing.Bitmap mergegeometry {
             get {
                 object obj = ResourceManager.GetObject("mergegeometry", resourceCulture);
@@ -571,6 +585,13 @@ namespace CodeImp.DoomBuilder.Properties {
             }
         }
         
+        internal static System.Drawing.Bitmap MergeGeoRemoveLines {
+            get {
+                object obj = ResourceManager.GetObject("MergeGeoRemoveLines", resourceCulture);
+                return ((System.Drawing.Bitmap)(obj));
+            }
+        }
+        
         internal static System.Drawing.Bitmap MissingTexture {
             get {
                 object obj = ResourceManager.GetObject("MissingTexture", resourceCulture);

Source/Core/Properties/Resources.resx

@@ -586,4 +586,13 @@
   <data name="Angle7" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\Angle7.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
+  <data name="MergeGeo" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\MergeGeo.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
+  <data name="MergeGeoClassic" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\MergeGeoClassic.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
+  <data name="MergeGeoRemoveLines" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\MergeGeoRemoveLines.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
 </root>

Source/Core/Resources/Actions.cfg

@@ -457,6 +457,36 @@ redo
 	allowscroll = true;
 }
 
+geomergeclassic //mxd
+{
+	title = "Merge Dragged Vertices Only";
+	category = "edit";
+	description = "Only vertex-line intersections will be processed when applying geometry drag or paste actions.";
+	allowkeys = true;
+	allowmouse = true;
+	allowscroll = false;
+}
+
+geomerge //mxd
+{
+	title = "Merge Dragged Geometry";
+	category = "edit";
+	description = "Geometry merging will be performed when applying geometry drag or paste actions.";
+	allowkeys = true;
+	allowmouse = true;
+	allowscroll = false;
+}
+
+georeplace //mxd
+{
+	title = "Replace with Dragged Geometry";
+	category = "edit";
+	description = "Dragged geometry will replace underlaying geometry when applying geometry drag or paste actions.";
+	allowkeys = true;
+	allowmouse = true;
+	allowscroll = false;
+}
+
 togglesnap
 {
 	title = "Snap to Grid";
@@ -469,9 +499,9 @@ togglesnap
 
 toggleautomerge
 {
-	title = "Merge Geometry";
+	title = "Snap to Geometry";
 	category = "edit";
-	description = "Toggles automatic merging of geometry for vertices and structures that are being dragged.";
+	description = "Toggles snapping to the nearest vertex or linedef for map elements that are being dragged.";
 	allowkeys = true;
 	allowmouse = true;
 	allowscroll = true;

Source/Core/Windows/MainForm.Designer.cs

@@ -97,6 +97,10 @@ namespace CodeImp.DoomBuilder.Windows
 			this.itemviewfloors = new System.Windows.Forms.ToolStripMenuItem();
 			this.itemviewceilings = new System.Windows.Forms.ToolStripMenuItem();
 			this.seperatorviewviews = new System.Windows.Forms.ToolStripSeparator();
+			this.itemmergegeoclassic = new System.Windows.Forms.ToolStripMenuItem();
+			this.itemmergegeo = new System.Windows.Forms.ToolStripMenuItem();
+			this.itemreplacegeo = new System.Windows.Forms.ToolStripMenuItem();
+			this.separatorgeomerge = new System.Windows.Forms.ToolStripSeparator();
 			this.itemfullbrightness = new System.Windows.Forms.ToolStripMenuItem();
 			this.itemtogglegrid = new System.Windows.Forms.ToolStripMenuItem();
 			this.toolStripSeparator4 = new System.Windows.Forms.ToolStripSeparator();
@@ -180,6 +184,10 @@ namespace CodeImp.DoomBuilder.Windows
 			this.buttonviewbrightness = new System.Windows.Forms.ToolStripButton();
 			this.buttonviewfloors = new System.Windows.Forms.ToolStripButton();
 			this.buttonviewceilings = new System.Windows.Forms.ToolStripButton();
+			this.separatorgeomergemodes = new System.Windows.Forms.ToolStripSeparator();
+			this.buttonmergegeoclassic = new System.Windows.Forms.ToolStripButton();
+			this.buttonmergegeo = new System.Windows.Forms.ToolStripButton();
+			this.buttonplacegeo = new System.Windows.Forms.ToolStripButton();
 			this.seperatorviews = new System.Windows.Forms.ToolStripSeparator();
 			this.buttontogglecomments = new System.Windows.Forms.ToolStripButton();
 			this.buttontogglefixedthingsscale = new System.Windows.Forms.ToolStripButton();
@@ -518,6 +526,10 @@ namespace CodeImp.DoomBuilder.Windows
             this.itempaste,
             this.itempastespecial,
             this.seperatoreditcopypaste,
+			this.itemmergegeoclassic,
+			this.itemmergegeo,
+			this.itemreplacegeo,
+			this.separatorgeomerge,
             this.itemsnaptogrid,
             this.itemdynamicgridsize,
             this.itemautomerge,
@@ -619,7 +631,7 @@ namespace CodeImp.DoomBuilder.Windows
 			this.itemautomerge.Name = "itemautomerge";
 			this.itemautomerge.Size = new System.Drawing.Size(219, 22);
 			this.itemautomerge.Tag = "builder_toggleautomerge";
-			this.itemautomerge.Text = "&Merge Geometry";
+			this.itemautomerge.Text = "Snap to &Geometry";
 			this.itemautomerge.Click += new System.EventHandler(this.InvokeTaggedAction);
 			// 
 			// itemautoclearsidetextures
@@ -819,6 +831,38 @@ namespace CodeImp.DoomBuilder.Windows
 			this.seperatorviewviews.Name = "seperatorviewviews";
 			this.seperatorviewviews.Size = new System.Drawing.Size(212, 6);
 			// 
+			// itemmergegeoclassic
+			// 
+			this.itemmergegeoclassic.Image = global::CodeImp.DoomBuilder.Properties.Resources.MergeGeoClassic;
+			this.itemmergegeoclassic.Name = "itemmergegeoclassic";
+			this.itemmergegeoclassic.Size = new System.Drawing.Size(215, 22);
+			this.itemmergegeoclassic.Tag = "builder_geomergeclassic";
+			this.itemmergegeoclassic.Text = "Merge Dragged Vertices Only";
+			this.itemmergegeoclassic.Click += new System.EventHandler(this.InvokeTaggedAction);
+			// 
+			// itemmergegeo
+			// 
+			this.itemmergegeo.Image = global::CodeImp.DoomBuilder.Properties.Resources.MergeGeo;
+			this.itemmergegeo.Name = "itemmergegeo";
+			this.itemmergegeo.Size = new System.Drawing.Size(215, 22);
+			this.itemmergegeo.Tag = "builder_geomerge";
+			this.itemmergegeo.Text = "Merge Dragged Geometry";
+			this.itemmergegeo.Click += new System.EventHandler(this.InvokeTaggedAction);
+			// 
+			// itemreplacegeo
+			// 
+			this.itemreplacegeo.Image = global::CodeImp.DoomBuilder.Properties.Resources.MergeGeoRemoveLines;
+			this.itemreplacegeo.Name = "itemreplacegeo";
+			this.itemreplacegeo.Size = new System.Drawing.Size(215, 22);
+			this.itemreplacegeo.Tag = "builder_georeplace";
+			this.itemreplacegeo.Text = "Replace with Dragged Geometry";
+			this.itemreplacegeo.Click += new System.EventHandler(this.InvokeTaggedAction);
+			// 
+			// separatorgeomerge
+			// 
+			this.separatorgeomerge.Name = "separatorgeomerge";
+			this.separatorgeomerge.Size = new System.Drawing.Size(212, 6);
+			// 
 			// itemfullbrightness
 			// 
 			this.itemfullbrightness.Checked = true;
@@ -1254,6 +1298,10 @@ namespace CodeImp.DoomBuilder.Windows
             this.buttonviewbrightness,
             this.buttonviewfloors,
             this.buttonviewceilings,
+			this.separatorgeomergemodes,
+			this.buttonmergegeoclassic,
+			this.buttonmergegeo,
+			this.buttonplacegeo,
             this.seperatorviews,
             this.buttonsnaptogrid,
             this.buttontoggledynamicgrid,
@@ -1645,6 +1693,48 @@ namespace CodeImp.DoomBuilder.Windows
 			this.buttonviewceilings.Text = "View Ceiling Textures";
 			this.buttonviewceilings.Click += new System.EventHandler(this.InvokeTaggedAction);
 			// 
+			// separatorgeomergemodes
+			// 
+			this.separatorgeomergemodes.Margin = new System.Windows.Forms.Padding(6, 0, 6, 0);
+			this.separatorgeomergemodes.Name = "separatorgeomergemodes";
+			this.separatorgeomergemodes.Size = new System.Drawing.Size(6, 25);
+			// 
+			// buttonmergegeoclassic
+			// 
+			this.buttonmergegeoclassic.CheckOnClick = true;
+			this.buttonmergegeoclassic.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
+			this.buttonmergegeoclassic.Image = global::CodeImp.DoomBuilder.Properties.Resources.MergeGeoClassic;
+			this.buttonmergegeoclassic.ImageTransparentColor = System.Drawing.Color.Magenta;
+			this.buttonmergegeoclassic.Name = "buttonmergegeoclassic";
+			this.buttonmergegeoclassic.Size = new System.Drawing.Size(23, 22);
+			this.buttonmergegeoclassic.Tag = "builder_geomergeclassic";
+			this.buttonmergegeoclassic.Text = "Merge Dragged Vertices Only";
+			this.buttonmergegeoclassic.Click += new System.EventHandler(this.InvokeTaggedAction);
+			// 
+			// buttonmergegeoclassic
+			// 
+			this.buttonmergegeo.CheckOnClick = true;
+			this.buttonmergegeo.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
+			this.buttonmergegeo.Image = global::CodeImp.DoomBuilder.Properties.Resources.MergeGeo;
+			this.buttonmergegeo.ImageTransparentColor = System.Drawing.Color.Magenta;
+			this.buttonmergegeo.Name = "buttonmergegeo";
+			this.buttonmergegeo.Size = new System.Drawing.Size(23, 22);
+			this.buttonmergegeo.Tag = "builder_geomerge";
+			this.buttonmergegeo.Text = "Merge Dragged Geometry";
+			this.buttonmergegeo.Click += new System.EventHandler(this.InvokeTaggedAction);
+			// 
+			// buttonmergegeoclassic
+			// 
+			this.buttonplacegeo.CheckOnClick = true;
+			this.buttonplacegeo.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
+			this.buttonplacegeo.Image = global::CodeImp.DoomBuilder.Properties.Resources.MergeGeoRemoveLines;
+			this.buttonplacegeo.ImageTransparentColor = System.Drawing.Color.Magenta;
+			this.buttonplacegeo.Name = "buttonmergegeoclassic";
+			this.buttonplacegeo.Size = new System.Drawing.Size(23, 22);
+			this.buttonplacegeo.Tag = "builder_georeplace";
+			this.buttonplacegeo.Text = "Replace with Dragged Geometry";
+			this.buttonplacegeo.Click += new System.EventHandler(this.InvokeTaggedAction);
+			// 
 			// seperatorviews
 			// 
 			this.seperatorviews.Margin = new System.Windows.Forms.Padding(6, 0, 6, 0);
@@ -1700,7 +1790,7 @@ namespace CodeImp.DoomBuilder.Windows
 			this.buttonautomerge.Name = "buttonautomerge";
 			this.buttonautomerge.Size = new System.Drawing.Size(23, 22);
 			this.buttonautomerge.Tag = "builder_toggleautomerge";
-			this.buttonautomerge.Text = "Merge Geometry";
+			this.buttonautomerge.Text = "Snap to Geometry";
 			this.buttonautomerge.Click += new System.EventHandler(this.InvokeTaggedAction);
 			// 
 			// buttonautoclearsidetextures
@@ -2607,6 +2697,10 @@ namespace CodeImp.DoomBuilder.Windows
 		private System.Windows.Forms.ToolStripButton buttonviewbrightness;
 		private System.Windows.Forms.ToolStripButton buttonviewfloors;
 		private System.Windows.Forms.ToolStripButton buttonviewceilings;
+		private System.Windows.Forms.ToolStripSeparator separatorgeomergemodes;
+		private System.Windows.Forms.ToolStripButton buttonmergegeoclassic;
+		private System.Windows.Forms.ToolStripButton buttonmergegeo;
+		private System.Windows.Forms.ToolStripButton buttonplacegeo;
 		private System.Windows.Forms.ToolStripSeparator seperatortoolsresources;
 		private System.Windows.Forms.ToolStripButton buttonscripteditor;
 		private System.Windows.Forms.ToolStripMenuItem menuview;
@@ -2617,6 +2711,10 @@ namespace CodeImp.DoomBuilder.Windows
 		private System.Windows.Forms.ToolStripMenuItem itemviewfloors;
 		private System.Windows.Forms.ToolStripMenuItem itemviewceilings;
 		private System.Windows.Forms.ToolStripSeparator seperatorviewzoom;
+		private System.Windows.Forms.ToolStripMenuItem itemmergegeoclassic;
+		private System.Windows.Forms.ToolStripMenuItem itemmergegeo;
+		private System.Windows.Forms.ToolStripMenuItem itemreplacegeo;
+		private System.Windows.Forms.ToolStripSeparator separatorgeomerge;
 		private System.Windows.Forms.ToolStripMenuItem itemscripteditor;
 		private System.Windows.Forms.ToolStripSeparator seperatortoolsconfig;
 		private System.Windows.Forms.ToolStripMenuItem itemtestmap;

Source/Core/Windows/MainForm.cs

@@ -138,6 +138,10 @@ namespace CodeImp.DoomBuilder.Windows
 		private ToolStripButton[] viewmodesbuttons;
 		private ToolStripMenuItem[] viewmodesitems;
 
+		//mxd. Geometry merge modes
+		private ToolStripButton[] geomergemodesbuttons;
+		private ToolStripMenuItem[] geomergemodesitems;
+		
 		// Edit modes
 		private List<ToolStripItem> editmodeitems;
 		
@@ -248,6 +252,17 @@ namespace CodeImp.DoomBuilder.Windows
 			viewmodesitems[(int)ViewMode.FloorTextures] = itemviewfloors;
 			viewmodesitems[(int)ViewMode.CeilingTextures] = itemviewceilings;
 
+			//mxd. Make arrays for geometry merge modes
+			int numgeomodes = Enum.GetValues(typeof(MergeGeometryMode)).Length;
+			geomergemodesbuttons = new ToolStripButton[numgeomodes];
+			geomergemodesbuttons[(int)MergeGeometryMode.CLASSIC] = buttonmergegeoclassic;
+			geomergemodesbuttons[(int)MergeGeometryMode.MERGE] = buttonmergegeo;
+			geomergemodesbuttons[(int)MergeGeometryMode.REPLACE] = buttonplacegeo;
+			geomergemodesitems = new ToolStripMenuItem[numgeomodes];
+			geomergemodesitems[(int)MergeGeometryMode.CLASSIC] = itemmergegeoclassic;
+			geomergemodesitems[(int)MergeGeometryMode.MERGE] = itemmergegeo;
+			geomergemodesitems[(int)MergeGeometryMode.REPLACE] = itemreplacegeo;
+			
 			// Visual Studio IDE doesn't let me set these in the designer :(
 			buttonzoom.Font = menufile.Font;
 			buttonzoom.DropDownDirection = ToolStripDropDownDirection.AboveLeft;
@@ -312,10 +327,18 @@ namespace CodeImp.DoomBuilder.Windows
 			}
 
 			// View mode only matters in classic editing modes
+			bool isclassicmode = (General.Editing.Mode is ClassicMode);
 			for(int i = 0; i < Renderer2D.NUM_VIEW_MODES; i++)
 			{
-				viewmodesitems[i].Enabled = (General.Editing.Mode is ClassicMode);
+				viewmodesitems[i].Enabled = isclassicmode;
-				viewmodesbuttons[i].Enabled = (General.Editing.Mode is ClassicMode);
+				viewmodesbuttons[i].Enabled = isclassicmode;
+			}
+
+			//mxd. Merge geometry mode only matters in classic editing modes
+			for(int i = 0; i < geomergemodesbuttons.Length; i++)
+			{
+				geomergemodesbuttons[i].Enabled = isclassicmode;
+				geomergemodesitems[i].Enabled = isclassicmode;
 			}
 
 			UpdateEditMenu();
@@ -2079,6 +2102,10 @@ namespace CodeImp.DoomBuilder.Windows
 			buttonviewceilings.Visible = General.Settings.ToolbarViewModes && maploaded;
 			buttonviewfloors.Visible = General.Settings.ToolbarViewModes && maploaded;
 			buttonviewnormal.Visible = General.Settings.ToolbarViewModes && maploaded;
+			separatorgeomergemodes.Visible = General.Settings.ToolbarGeometry && maploaded; //mxd
+			buttonmergegeoclassic.Visible = General.Settings.ToolbarGeometry && maploaded; //mxd
+			buttonmergegeo.Visible = General.Settings.ToolbarGeometry && maploaded; //mxd
+			buttonplacegeo.Visible = General.Settings.ToolbarGeometry && maploaded; //mxd
 			buttonsnaptogrid.Visible = General.Settings.ToolbarGeometry && maploaded;
 			buttontoggledynamicgrid.Visible = General.Settings.ToolbarGeometry && maploaded; //mxd
 			buttontoggledynamicgrid.Checked = General.Settings.DynamicGridSize; //mxd
@@ -2756,6 +2783,17 @@ namespace CodeImp.DoomBuilder.Windows
 			buttoncut.Enabled = itemcut.Enabled;
 			buttoncopy.Enabled = itemcopy.Enabled;
 			buttonpaste.Enabled = itempaste.Enabled;
+
+			//mxd. Geometry merge mode items
+			if(General.Map != null)
+			{
+				for(int i = 0; i < geomergemodesbuttons.Length; i++)
+				{
+					// Check the correct item
+					geomergemodesbuttons[i].Checked = (i == (int)General.Settings.MergeGeometryMode);
+					geomergemodesitems[i].Checked = (i == (int)General.Settings.MergeGeometryMode);
+				}
+			}
 		}
 
 		//mxd
@@ -2919,6 +2957,36 @@ namespace CodeImp.DoomBuilder.Windows
 			f.ShowDialog(this);
 		}
 
+		//mxd
+		[BeginAction("geomergeclassic")]
+		private void GeoMergeClassic()
+		{
+			General.Settings.MergeGeometryMode = MergeGeometryMode.CLASSIC;
+			UpdateToolbar();
+			UpdateEditMenu();
+			DisplayStatus(StatusType.Action, "\"Merge Dragged Vertices Only\" mode selected");
+		}
+
+		//mxd
+		[BeginAction("geomerge")]
+		private void GeoMerge()
+		{
+			General.Settings.MergeGeometryMode = MergeGeometryMode.MERGE;
+			UpdateToolbar();
+			UpdateEditMenu();
+			DisplayStatus(StatusType.Action, "\"Merge Dragged Geometry\" mode selected");
+		}
+
+		//mxd
+		[BeginAction("georeplace")]
+		private void GeoReplace()
+		{
+			General.Settings.MergeGeometryMode = MergeGeometryMode.REPLACE;
+			UpdateToolbar();
+			UpdateEditMenu();
+			DisplayStatus(StatusType.Action, "\"Replace with Dragged Geometry\" mode selected");
+		}
+		
 		#endregion
 
 		#region ================== View Menu

Source/Plugins/BuilderModes/ClassicModes/DragGeometryMode.cs

@@ -420,7 +420,7 @@ namespace CodeImp.DoomBuilder.BuilderModes
 				MoveGeometryRelative(mousemappos - dragstartmappos, snaptogrid, snaptogridincrement, snaptonearest, snaptocardinaldirection);
 
 				// Stitch geometry
-				General.Map.Map.StitchGeometry(true);
+				General.Map.Map.StitchGeometry(General.Settings.MergeGeometryMode);
 				
 				// Snap to map format accuracy
 				General.Map.Map.SnapAllToAccuracy();

Source/Plugins/BuilderModes/ClassicModes/EditSelectionMode.cs

@@ -1645,8 +1645,11 @@ namespace CodeImp.DoomBuilder.BuilderModes
 					}
 				}
 
+				//mxd. We'll need sidedefs marked by StitchGeometry, not all sidedefs from selection...
+				General.Map.Map.ClearMarkedSidedefs(false);
+
 				// Stitch geometry
-				General.Map.Map.StitchGeometry(true);
+				General.Map.Map.StitchGeometry(General.Settings.MergeGeometryMode);
 
 				// Snap to map format accuracy
 				General.Map.Map.SnapAllToAccuracy(General.Map.UDMF && usepreciseposition);