Extract drawing from PPE to InteractionLayer

- Eliminate event bindings, invoke DrawEditor directly

MatterControlLib/PartPreviewWindow/View3D/InteractionLayer.cs

@@ -49,8 +49,6 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 
 		public InteractiveScene Scene { get; }
 
-		public event EventHandler<DrawEventArgs> DrawGlOpaqueContent;
-
 		public bool DoOpenGlDrawing { get; set; } = true;
 
 		// TODO: Collapse into auto-property
@@ -118,7 +116,6 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 				GLHelper.SetGlContext(this.World, renderSource.TransformToScreenSpace(renderSource.LocalBounds), lighting);
 
 				// Draw Gl Content
-				DrawGlOpaqueContent?.Invoke(this, e);
 				this.DrawGlTransparentContent(e);
 
 				GLHelper.UnsetGlContext();

MatterControlLib/PartPreviewWindow/View3D/MeshViewerWidget.cs

@@ -442,6 +442,14 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 				{
 					DrawObject(object3D, transparentMeshes, e);
 				}
+
+				// Invoke existing IEditorDraw when iterating items
+				if (object3D is IEditorDraw editorDraw)
+				{
+					// TODO: Putting the drawing code in the IObject3D means almost certain bindings to MatterControl in IObject3D. If instead
+					// we had a UI layer object that used binding to register scene drawing hooks for specific types, we could avoid the bindings
+					editorDraw.DrawEditor(this, e);
+				}
 			}
 
 			transparentMeshes.Sort(BackToFrontXY);