+ void Ref() noexcept { ++ref_count; }
+ void UnRef() noexcept { --ref_count; }
+ bool Referenced() const noexcept { return ref_count > 0; }
+
+ void Invalidate() noexcept { dirty_model = dirty_save = true; }
+ void InvalidateModel() noexcept { dirty_model = true; }
+ void ClearModel() noexcept { dirty_model = false; }
+ void ClearSave() noexcept { dirty_save = false; }
+ bool ShouldUpdateModel() const noexcept { return dirty_model; }
+ bool ShouldUpdateSave() const noexcept { return dirty_save; }
+
+ void Update(BlockModel &) noexcept;