decal material draw order

com.unity.render-pipelines.high-definition/HDRP/Editor/Material/Decal/DecalUI.cs

             public static GUIContent decalBlendText = new GUIContent("Global Opacity", "Whole decal Opacity");
             public static GUIContent AlbedoModeText = new GUIContent("Affect BaseColor", "Base color + Opacity, Opacity only");
  			public static GUIContent MeshDecalDepthBiasText = new GUIContent("Mesh decal depth bias", "prevents z-fighting");
+	 		public static GUIContent DrawOrderText = new GUIContent("Draw order", "Controls draw order of decal projectors");
 
             public static GUIContent[] maskMapText =
             {
         protected MaterialProperty decalMeshDepthBias = new MaterialProperty();
         protected const string kDecalMeshDepthBias = "_DecalMeshDepthBias";
 
+        protected MaterialProperty drawOrder = new MaterialProperty();
+        protected const string kDrawOrder = "_DrawOrder";
+
         protected MaterialEditor m_MaterialEditor;
 
         // This is call by the inspector
             maskBlendMode = FindProperty(kMaskBlendMode, props);
             maskmapMetal = FindProperty(kMaskmapMetal, props);
             maskmapAO = FindProperty(kMaskmapAO, props);
-            maskmapSmoothness = FindProperty(kMaskmapSmoothness, props);
-            decalMeshDepthBias = FindProperty(kDecalMeshDepthBias, props);
-            
+            maskmapSmoothness = FindProperty(kMaskmapSmoothness, props);            
+            decalMeshDepthBias = FindProperty(kDecalMeshDepthBias, props);            
+            drawOrder = FindProperty(kDrawOrder, props);
+
             // always instanced
             SerializedProperty instancing = m_MaterialEditor.serializedObject.FindProperty("m_EnableInstancingVariants");
             instancing.boolValue = true;
                     }
                     EditorGUI.indentLevel--;
                 }
+                m_MaterialEditor.ShaderProperty(drawOrder, Styles.DrawOrderText);
                 m_MaterialEditor.ShaderProperty(decalBlend, Styles.decalBlendText);
                 m_MaterialEditor.ShaderProperty(decalMeshDepthBias, Styles.MeshDecalDepthBiasText);
                 EditorGUI.indentLevel--;

com.unity.render-pipelines.high-definition/HDRP/Material/Decal/Decal.shader

 		[ToggleUI] _MaskmapAO("_MaskmapAO", Range(0.0, 1.0)) = 0.0
 		[ToggleUI] _MaskmapSmoothness("_MaskmapSmoothness", Range(0.0, 1.0)) = 1.0
 		[HideInInspector] _DecalMeshDepthBias("_DecalMeshDepthBias", Float) = 0.0 
+		[HideInInspector] _DrawOrder("_DrawOrder", Int) = 0
     }
 
     HLSLINCLUDE

com.unity.render-pipelines.high-definition/HDRP/Material/Decal/DecalSystem.cs

         static public float[] m_BoundingDistances = new float[1];
 
         private Dictionary<int, DecalSet> m_DecalSets = new Dictionary<int, DecalSet>();
+        private SortedDictionary<int, DecalSet> m_DecalSetsRenderList = new SortedDictionary<int, DecalSet>();
 
         // current camera
         private Camera m_Camera;
                 }
             }
 
-            public void CreateDrawData()
+            public bool CreateDrawData()
-                    return;
+                    return false;
-                    return;
+                    return false;
 
                 int instanceCount = 0;
                 int batchCount = 0;
                 { 
                     AddToTextureList(ref instance.m_TextureList);
                 }
+                return true;
             }
 
             public void EndCull()
                 }
             }
 
+            public int DrawOrder
+            {
+                get
+                {
+                    return this.m_Material.GetInt("_DrawOrder");
+                }
+            }
+
             private List<Matrix4x4[]> m_DecalToWorld = new List<Matrix4x4[]>();
             private List<Matrix4x4[]> m_NormalToWorld = new List<Matrix4x4[]>();
 
             if (m_DecalMesh == null)
                 m_DecalMesh = CoreUtils.CreateCubeMesh(kMin, kMax);
 
-            foreach (var pair in m_DecalSets)
+            foreach (var pair in m_DecalSetsRenderList)
             {
                 pair.Value.RenderIntoDBuffer(cmd);
             }
                 m_MaskTextureScaleBias = new TextureScaleBias[newDecalDatasSize];
                 m_BaseColor = new Vector4[newDecalDatasSize];
             }
+
+            m_DecalSetsRenderList.Clear();
-                pair.Value.CreateDrawData();
+                if (pair.Value.CreateDrawData())
+                {
+                    m_DecalSetsRenderList.Add(pair.Value.DrawOrder, pair.Value);
+                }
             }
         }