Changed emissive mesh update system to support multi-inspector

com.unity.render-pipelines.high-definition/HDRP/Editor/Lighting/HDLightEditor.Styles.cs

             public readonly GUIContent shapeWidthBox = new GUIContent("Size X", "");
             public readonly GUIContent shapeHeightBox = new GUIContent("Size Y", "");
             public readonly GUIContent applyRangeAttenuation = new GUIContent("Apply Range Attenuation", "Allows disabling range attenuation. This is useful indoor (like a room) to avoid having to setup a large range for a light to get correct inverse square attenuation that may leak out of the indoor");
-            public readonly GUIContent showEmissiveMesh = new GUIContent("Show Emissive Mesh", "Generate an emissive mesh using the size and intensity of the light");
+            public readonly GUIContent showEmissiveMesh = new GUIContent("Show Emissive Mesh", "Generate an emissive mesh using the size, color and intensity of the light");
 
             public readonly GUIContent shape = new GUIContent("Type", "Specifies the current type of light. Possible types are Directional, Spot, Point, Rectangle and Line lights.");
             public readonly GUIContent[] shapeNames;

com.unity.render-pipelines.high-definition/HDRP/Editor/Lighting/HDLightEditor.cs

         HDAdditionalLightData[]     m_AdditionalLightDatas;
         AdditionalShadowData[]      m_AdditionalShaodowDatas;
 
+        // Used to detect if the scale have been changed via the transform component
+        Vector3 m_OldLightSize;
+        bool m_UpdateEmissiveMesh;
+
         protected override void OnEnable()
         {
             base.OnEnable();
             m_SerializedAdditionalShadowData.ApplyModifiedProperties();
             m_SerializedAdditionalLightData.ApplyModifiedProperties();
             settings.ApplyModifiedProperties();
+
+            if (m_UpdateEmissiveMesh)
+                UpdateEmissiveMesh();
         }
 
         void DrawFoldout(SerializedProperty foldoutProperty, string title, Action func)
             if (EditorGUI.EndChangeCheck())
             {
                 UpdateLightIntensity();
-                UpdateEmissiveMesh();
+                m_UpdateEmissiveMesh = true;
                 ((Light)target).SetLightDirty(); // Should be apply only to parameter that's affect GI, but make the code cleaner
             }
         }
                 GameObject    lightGameObject = lightData.gameObject;
                 MeshRenderer  emissiveMeshRenderer = lightData.GetComponent<MeshRenderer>();
                 MeshFilter    emissiveMeshFilter = lightData.GetComponent<MeshFilter>();
+                Light         light = lightGameObject.GetComponent<Light>();
 
                 bool showEmissiveMesh = IsAreaLightShape(m_LightShape) && m_LightShape != LightShape.Line && m_AdditionalLightData.showEmissiveMesh.boolValue;
 
                 }
 
                 float areaLightIntensity = 0;
-                
+
-                        lightGameObject.transform.localScale = new Vector3(m_AdditionalLightData.shapeWidth.floatValue, m_AdditionalLightData.shapeHeight.floatValue, 0);
+                        lightGameObject.transform.localScale = new Vector3(lightData.shapeWidth, lightData.shapeHeight, 0);
-                            settings.intensity.floatValue,
-                            m_AdditionalLightData.shapeWidth.floatValue,
-                            m_AdditionalLightData.shapeHeight.floatValue);
+                            light.intensity,
+                            lightData.shapeWidth,
+                            lightData.shapeHeight);
                         break;
                     default:
                         break;
                     emissiveMeshRenderer.material = new Material(Shader.Find("HDRenderPipeline/Unlit"));
                 
                 emissiveMeshRenderer.sharedMaterial.SetColor("_UnlitColor", Color.black);
-                emissiveMeshRenderer.sharedMaterial.SetColor("_EmissiveColor", settings.color.colorValue * areaLightIntensity);
+                emissiveMeshRenderer.sharedMaterial.SetColor("_EmissiveColor", light.color * areaLightIntensity);
             }
         }
 
             // Early exit if the light type is not an area
-            if (!IsAreaLightShape(m_LightShape) || target == null)
+            if (!IsAreaLightShape(m_LightShape) || target == null || targets.Length > 1)
+            if (lightSize == m_OldLightSize)
+                return ;
+
             switch (m_LightShape)
             {
                 case LightShape.Rectangle:
                 default:
                     break;
             }
+
+            UpdateLightIntensity();
+            m_UpdateEmissiveMesh = true;
+
+            m_OldLightSize = lightSize;
         }
 
         // Caution: this function must match the one in HDAdditionalLightData.ConvertPhysicalLightIntensityToLightIntensity - any change need to be replicated
             EditorGUI.BeginChangeCheck();
             settings.DrawColor();
             if (EditorGUI.EndChangeCheck())
-                UpdateEmissiveMesh();
+                m_UpdateEmissiveMesh = true;
 
             EditorGUI.BeginChangeCheck();
 
             if (EditorGUI.EndChangeCheck())
             {
                 UpdateLightIntensity();
-                UpdateEmissiveMesh();
+                m_UpdateEmissiveMesh = true;
             }
 
             settings.DrawBounceIntensity();
             if (IsAreaLightShape(m_LightShape))
             {
                 EditorGUI.BeginChangeCheck();
-                EditorGUILayout.PropertyField(m_AdditionalLightData.showEmissiveMesh);
+                EditorGUILayout.PropertyField(m_AdditionalLightData.showEmissiveMesh, s_Styles.showEmissiveMesh);
-                    UpdateEmissiveMesh();
+                    m_UpdateEmissiveMesh = true;
             }
 
             if (m_AdditionalLightData.showAdditionalSettings.boolValue)