Merge pull request #1816 from Unity-Technologies/HDRP/decals/v2_1/ghost_fix

Hdrp/decals/v2 1/ghost fix

com.unity.render-pipelines.high-definition/CHANGELOG.md

 
 ### Fixed
 - Fix HDReflectionProbe offset displayed in gizmo different than what is affected.
+- Fix decals getting into a state where they could not be removed or disabled.
 
 ## [3.1.0-preview]
 

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

         public event OnMaterialChangeDelegate OnMaterialChange;
 
         public void OnValidate()
-        {
-            // handle material changes
-            if (m_OldMaterial != m_Material)
+        {            
+            if (m_Handle != null) // don't do anything if OnEnable hasn't been called yet when scene is loading.
-                if (m_Handle != null)
-                    DecalSystem.instance.RemoveDecal(m_Handle);
-                m_Handle = DecalSystem.instance.AddDecal(transform, sizeOffset, m_DrawDistance, m_FadeScale, uvScaleBias, m_AffectsTransparency, m_Material);
-                m_OldMaterial = m_Material;
+                // handle material changes, because decals are stored as sets sorted by material, if material changes decal needs to be removed and re-added to that it goes into correct set
+                if (m_OldMaterial != m_Material)
+                {
+                    DecalSystem.instance.RemoveDecal(m_Handle);
+                    m_Handle = DecalSystem.instance.AddDecal(transform, sizeOffset, m_DrawDistance, m_FadeScale, uvScaleBias, m_AffectsTransparency, m_Material);
+                    m_OldMaterial = m_Material;
-                // notify the editor that material has changed so it can update the shader foldout
-                if (OnMaterialChange != null)
+                    // notify the editor that material has changed so it can update the shader foldout
+                    if (OnMaterialChange != null)
+                    {
+                        OnMaterialChange();
+                    }
+                }
+                else // no material change, just update whatever else changed
-                    OnMaterialChange();
+                    DecalSystem.instance.UpdateCachedData(transform, sizeOffset, m_DrawDistance, m_FadeScale, uvScaleBias, m_AffectsTransparency, m_Handle);
                 }
             }