Combine can subtract holes

MatterControlLib/ApplicationView/SceneOperations.cs

@@ -1073,37 +1073,12 @@ namespace MatterHackers.MatterControl
 			return new SceneOperation("Group")
 			{
 				OperationType = typeof(SelectionGroupObject3D),
-				ResultType = typeof(GroupObject3D),
+				ResultType = typeof(GroupHolesAppliedObject3D),
 				TitleGetter = () => "Group".Localize(),
 				Action = (sceneContext) =>
 				{
-					var scene = sceneContext.Scene;
-					var selectedItem = scene.SelectedItem;
-					scene.SelectedItem = null;
-
-					var newGroup = new GroupObject3D();
-					// When grouping items, move them to be centered on their bounding box
-					newGroup.Children.Modify((gChildren) =>
-					{
-						selectedItem.Clone().Children.Modify((sChildren) =>
-						{
-							var center = selectedItem.GetAxisAlignedBoundingBox().Center;
-
-							foreach (var child in sChildren)
-							{
-								child.Translate(-center.X, -center.Y, 0);
-								gChildren.Add(child);
-							}
-
-							newGroup.Translate(center.X, center.Y, 0);
-						});
-					});
-
-					scene.UndoBuffer.AddAndDo(new ReplaceCommand(selectedItem.Children.ToList(), new[] { newGroup }));
-
-					newGroup.MakeNameNonColliding();
-
-					scene.SelectedItem = newGroup;
+					var group = new GroupHolesAppliedObject3D();
+					group.WrapSelectedItemAndSelect(sceneContext.Scene);
 				},
 				HelpTextGetter = () => "At least 2 parts must be selected".Localize().Stars(),
 				IsEnabled = (sceneContext) => sceneContext.Scene is InteractiveScene scene
@@ -1534,6 +1509,7 @@ namespace MatterHackers.MatterControl
 					if (selectedItem != null)
 					{
 						return selectedItem is GroupObject3D
+							|| selectedItem is GroupHolesAppliedObject3D
 							|| selectedItem.GetType() == typeof(Object3D)
 							|| selectedItem.CanApply;
 					}

MatterControlLib/DesignTools/Operations/GroupObject3D.cs

@@ -29,10 +29,14 @@ either expressed or implied, of the FreeBSD Project.
 
 using MatterHackers.DataConverters3D;
 using MatterHackers.Localizations;
+using MatterHackers.MatterControl.PartPreviewWindow.View3D;
+using System;
+using System.Linq;
+using System.Text.Json.Serialization;
 
 namespace MatterHackers.MatterControl.DesignTools.Operations
 {
-    public class GroupObject3D : Object3D
+	public class GroupObject3D : Object3D
 	{
 		public override bool CanApply => true;
 
@@ -41,4 +45,33 @@ namespace MatterHackers.MatterControl.DesignTools.Operations
 			Name = "Group".Localize();
 		}
 	}
+
+	[ShowUpdateButton(Show = false)]
+	public class GroupHolesAppliedObject3D : SubtractObject3D_2
+	{
+		public GroupHolesAppliedObject3D()
+		{
+			Name = "Group".Localize();
+		}
+
+		public override SelectedChildren SelectedChildren 
+		{
+			get
+            {
+				var selections = new SelectedChildren();
+
+				foreach(var child in SourceContainer.DescendantsAndSelfMultipleChildrenFirstOrSelf().Children.Where(i => i.WorldOutputType(this) == PrintOutputTypes.Hole))
+                {
+					selections.Add(child.ID);
+                }
+
+				return selections;
+			}
+
+			set
+            {
+
+            }
+		}
+	}
 }

MatterControlLib/DesignTools/Primitives/ComponentObject3D.cs

@@ -110,7 +110,7 @@ namespace MatterHackers.MatterControl.DesignTools
 
 				if (newChildren.Count > 1)
 				{
-					var group = new GroupObject3D
+					var group = new GroupHolesAppliedObject3D
 					{
 						Name = this.Name
 					};

MatterControlLib/PartPreviewWindow/View3D/Actions/SubtractObject3D_2.cs

@@ -54,7 +54,7 @@ namespace MatterHackers.MatterControl.PartPreviewWindow.View3D
 		}
 
 		[DisplayName("Part(s) to Subtract")]
-		public SelectedChildren SelectedChildren { get; set; } = new SelectedChildren();
+		public virtual SelectedChildren SelectedChildren { get; set; } = new SelectedChildren();
 
 #if DEBUG
 		public ProcessingModes Processing { get; set; } = ProcessingModes.Polygons;

StaticData/Translations/Master.txt

@@ -4339,6 +4339,9 @@ Translated:Select this option only if your printer does not appear in the list
 English:Select What to Import
 Translated:Select What to Import
 
+English:Selected Children
+Translated:Selected Children
+
 English:Selected Material and Bed Surface are Incompatable
 Translated:Selected Material and Bed Surface are Incompatable