Add logic to check for inherited PropertyDrawers from base classes and interfaces

This way an inherited drawer will be used if it exists, which might not be too uncommon in the case of SerializeReference fields

Author: JohannesDeml

Assets/MackySoft/MackySoft.SerializeReferenceExtensions/Editor/PropertyDrawerCache.cs

@@ -25,6 +25,8 @@ public static bool TryGetPropertyDrawer (Type type,out PropertyDrawer drawer)
 
 		static Type GetCustomPropertyDrawerType (Type type)
 		{
+			Type[] interfaceTypes = type.GetInterfaces();
+			
 			foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())
 			{
 				foreach (Type drawerType in assembly.GetTypes())
@@ -36,9 +38,39 @@ static Type GetCustomPropertyDrawerType (Type type)
 						if (field != null)
 						{
 							var fieldType = field.GetValue(customPropertyDrawer) as Type;
-							if (fieldType != null && fieldType == type)
+							if (fieldType != null)
 							{
-								return drawerType;
+								if (fieldType == type)
+								{
+									return drawerType;
+								}
+								
+								// If the property drawer also allows for being applied to child classes, check if they match
+								var useForChildrenField = customPropertyDrawer.GetType().GetField("m_UseForChildren", BindingFlags.NonPublic | BindingFlags.Instance);
+								if (useForChildrenField != null)
+								{
+									object useForChildrenValue = useForChildrenField.GetValue(customPropertyDrawer);
+									if (useForChildrenValue is bool && (bool)useForChildrenValue)
+									{
+										// Check interfaces
+										if (Array.Exists(interfaceTypes, interfaceType => interfaceType == fieldType))
+										{
+											return drawerType;
+										}
+
+										// Check derived types
+										Type baseType = type.BaseType;
+										while (baseType != null)
+										{
+											if (baseType == fieldType)
+											{
+												return drawerType;
+											}
+
+											baseType = baseType.BaseType;
+										}
+									}
+								}
 							}
 						}
 					}