fix compile error on 2018.3

Author: Karl Henkel

com.unity.probuilder/Editor/EditorCore/StaticEditorMeshHandles.cs

@@ -11,7 +11,6 @@ namespace UnityEditor.ProBuilder
 	partial class EditorMeshHandles
 	{
 		static bool s_Initialized;
-
 		static Material s_LineMaterial;
 		static Material s_FaceMaterial;
 
@@ -51,7 +50,7 @@ internal static void DrawGizmo(Vector3 position, Quaternion rotation, float size
 		internal static void DrawGizmo(Vector3 position, Matrix4x4 matrix, float size = -1f)
 		{
 			var p = matrix.MultiplyPoint3x4(position);
-			size = HandleUtility.GetHandleSize(p) * size < 0f ? .25f : size;
+			size = HandleUtility.GetHandleSize(p) * size < 0f ? .2f : size;
 
 			using (var lineDrawer = new LineDrawingScope(Color.green, -1f, CompareFunction.Always))
 			{

com.unity.probuilder/Editor/EditorCore/VertexTool.cs

@@ -8,6 +8,9 @@ namespace UnityEditor.ProBuilder
 	abstract class VertexTool : VertexManipulationTool
 	{
 		const bool k_CollectCoincidentVertices = true;
+#if APPLY_POSITION_TO_SPACE_GIZMO
+		Matrix4x4 m_CurrentDelta = Matrix4x4.identity;
+#endif
 
 		class MeshAndPositions : MeshAndElementGroupPair
 		{
@@ -36,7 +39,7 @@ protected override MeshAndElementGroupPair GetMeshAndElementGroupPair (ProBuilde
 
 		protected override void DoTool(Vector3 position, Quaternion rotation)
 		{
-			if (isEditing && currentEvent.type == EventType.Repaint)
+			if ( isEditing && currentEvent.type == EventType.Repaint)
 			{
 				foreach (var key in meshAndElementGroupPairs)
 				{
@@ -60,14 +63,23 @@ protected override void DoTool(Vector3 position, Quaternion rotation)
 								}
 							}
 #endif
+
+#if APPLY_POSITION_TO_SPACE_GIZMO
+						EditorMeshHandles.DrawGizmo(Vector3.zero, group.matrix.inverse * m_CurrentDelta);
+#else
 						EditorMeshHandles.DrawGizmo(Vector3.zero, group.matrix.inverse);
+#endif
 					}
 				}
 			}
 		}
 
 		protected void Apply(Matrix4x4 delta)
 		{
+#if APPLY_POSITION_TO_SPACE_GIZMO
+			m_CurrentDelta.SetColumn(3, delta.GetColumn(3));
+#endif
+
 			foreach (var key in meshAndElementGroupPairs)
 			{
 				if (!(key is MeshAndPositions))

com.unity.probuilder/Settings/Editor/UserSettingsProvider.cs

@@ -9,8 +9,12 @@
 using System.Reflection;
 using UnityEngine;
 #if SETTINGS_PROVIDER_ENABLED
+#if UNITY_2018_3
+using UnityEngine.Experimental.UIElements;
+#else
 using UnityEngine.UIElements;
 #endif
+#endif
 
 namespace UnityEditor.SettingsManagement
 {