diff --git a/Source/Core/Builder.csproj b/Source/Core/Builder.csproj
index 5b1ede18..41245a24 100644
--- a/Source/Core/Builder.csproj
+++ b/Source/Core/Builder.csproj
@@ -804,6 +804,7 @@
     <Compile Include="Windows\FlagsForm.Designer.cs">
       <DependentUpon>FlagsForm.cs</DependentUpon>
     </Compile>
+    <Compile Include="Windows\ISectorEditForm.cs" />
     <Compile Include="Windows\MenuSection.cs" />
     <Compile Include="Windows\PasteOptionsForm.cs">
       <SubType>Form</SubType>
diff --git a/Source/Core/Windows/ISectorEditForm.cs b/Source/Core/Windows/ISectorEditForm.cs
new file mode 100644
index 00000000..07c7e7e7
--- /dev/null
+++ b/Source/Core/Windows/ISectorEditForm.cs
@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using CodeImp.DoomBuilder.Map;
+
+namespace CodeImp.DoomBuilder.Windows
+{
+	public interface ISectorEditForm
+	{
+		event EventHandler OnValuesChanged;
+		ICollection<Sector> Selection { get; }
+	}
+}
diff --git a/Source/Core/Windows/MainForm.cs b/Source/Core/Windows/MainForm.cs
index de9f3233..08f95562 100644
--- a/Source/Core/Windows/MainForm.cs
+++ b/Source/Core/Windows/MainForm.cs
@@ -3008,6 +3008,7 @@ namespace CodeImp.DoomBuilder.Windows
 			if(General.Map.UDMF){ //mxd
 				SectorEditFormUDMF f = new SectorEditFormUDMF();
 				f.Setup(sectors);
+				f.OnValuesChanged += new EventHandler(EditForm_OnValuesChanged);
 				result = f.ShowDialog(this);
 				f.Dispose();
 			}else{
diff --git a/Source/Core/Windows/SectorEditForm.cs b/Source/Core/Windows/SectorEditForm.cs
index 1ae32ac4..5f5a89c5 100644
--- a/Source/Core/Windows/SectorEditForm.cs
+++ b/Source/Core/Windows/SectorEditForm.cs
@@ -26,7 +26,7 @@ using CodeImp.DoomBuilder.Types;
 
 namespace CodeImp.DoomBuilder.Windows
 {
-	public partial class SectorEditForm : DelayedForm
+	public partial class SectorEditForm : DelayedForm, ISectorEditForm
 	{
 		#region ================== Events
 
@@ -42,8 +42,6 @@ namespace CodeImp.DoomBuilder.Windows
 
 		private struct SectorProperties //mxd
 		{
-			//public int Tag;
-			//public int Effect;
 			public int Brightness;
 			public int FloorHeight;
 			public int CeilHeight;
@@ -51,8 +49,6 @@ namespace CodeImp.DoomBuilder.Windows
 			public string CeilTexture;
 
 			public SectorProperties(Sector s) {
-				//Tag = s.Tag;
-				//Effect = s.Effect;
 				Brightness = s.Brightness;
 				FloorHeight = s.FloorHeight;
 				CeilHeight = s.CeilHeight;
diff --git a/Source/Core/Windows/SectorEditFormUDMF.cs b/Source/Core/Windows/SectorEditFormUDMF.cs
index a47a8315..962679e4 100644
--- a/Source/Core/Windows/SectorEditFormUDMF.cs
+++ b/Source/Core/Windows/SectorEditFormUDMF.cs
@@ -8,12 +8,29 @@ using CodeImp.DoomBuilder.GZBuilder.Tools;
 
 namespace CodeImp.DoomBuilder.Windows
 {
-	public partial class SectorEditFormUDMF : DelayedForm
+	public partial class SectorEditFormUDMF : DelayedForm, ISectorEditForm
 	{
-		// Variables
+		#region ================== Events
+
+		public event EventHandler OnValuesChanged; //mxd
+
+		#endregion
+
+		#region ================== Variables
+
 		private ICollection<Sector> sectors;
 		private List<CheckBox> flags;
-		
+
+		#endregion
+
+		#region ================== Properties
+
+		public ICollection<Sector> Selection { get { return sectors; } } //mxd
+
+		#endregion
+
+		#region ================== Constructor
+
 		public SectorEditFormUDMF() {
 			InitializeComponent();
 
@@ -40,6 +57,10 @@ namespace CodeImp.DoomBuilder.Windows
 			fieldslist.Setup("sector");
 		}
 
+		#endregion
+
+		#region ================== Methods
+
 		// This sets up the form to edit the given sectors
 		public void Setup(ICollection<Sector> sectors) {
 			Sector sc;
@@ -236,6 +257,10 @@ namespace CodeImp.DoomBuilder.Windows
 			}
 		}
 
+		#endregion
+
+		#region ================== Events
+
 		private void apply_Click(object sender, EventArgs e) {
 			string undodesc = "sector";
 
@@ -362,6 +387,10 @@ namespace CodeImp.DoomBuilder.Windows
 
 			// Done
 			General.Map.IsChanged = true;
+
+			//dbg
+			if(OnValuesChanged != null) OnValuesChanged(this, EventArgs.Empty);
+
 			this.DialogResult = DialogResult.OK;
 			this.Close();
 		}
@@ -408,5 +437,7 @@ namespace CodeImp.DoomBuilder.Windows
 		private void ceilRotation_WhenTextChanged(object sender, EventArgs e) {
 			ceilAngleControl.Angle = General.ClampAngle(360 - ceilRotation.GetResult(0));
 		}
+
+		#endregion
 	}
 }
diff --git a/Source/Plugins/BuilderModes/VisualModes/BaseVisualGeometrySector.cs b/Source/Plugins/BuilderModes/VisualModes/BaseVisualGeometrySector.cs
index f4fadc7b..d815fd43 100644
--- a/Source/Plugins/BuilderModes/VisualModes/BaseVisualGeometrySector.cs
+++ b/Source/Plugins/BuilderModes/VisualModes/BaseVisualGeometrySector.cs
@@ -243,13 +243,7 @@ namespace CodeImp.DoomBuilder.BuilderModes
 			Linedef targetLine = MapSet.NearestLinedef(lines, hitpos);
 			if(targetLine == null) return;
 
-			foreach(Sidedef side in highlightedSector.Sidedefs) {
-				if(side.Line == targetLine && side.Line.Front != null && side.Line.Front == side) {
-					isFront = true;
-					break;
-				}
-			}
-
+			isFront = targetLine.SideOfLine(hitpos) > 0;
 			Sector.Sector.Fields.BeforeFieldsChange();
 
 			//find an angle to rotate texture
@@ -652,7 +646,7 @@ namespace CodeImp.DoomBuilder.BuilderModes
 
 		//mxd
 		private void Interface_OnEditFormValuesChanged(object sender, System.EventArgs e) {
-			SectorEditForm form = sender as SectorEditForm;
+			ISectorEditForm form = sender as ISectorEditForm;
 			if(form == null) return;
 
 			// Update what must be updated