Disallow direct events construction from JSON

Direct construction (using makeEvent() or explicitly constructing
an event) from JSON may create an event that has a type conflicting
with that stored in JSON. There's no such problem with loadEvent(),
even though it's considerably slower. Driven by the fact that almost
nowhere in the code direct construction is used on checked JSON
(one test is the only valid case), this commit moves all JSON-loading
constructors to the protected section, thereby disabling usage of
makeEvent() in JSON-loading capacity, and switches such cases across
the library to loadEvent().

1 files changed, 9 insertions, 2 deletions

diff --git a/lib/events/event.h b/lib/events/event.h
index 6a7acf28..9d7c61a9 100644
--- a/lib/events/event.h
+++ b/lib/events/event.h
@@ -203,6 +203,9 @@ private:
 // === Event creation facilities ===
 
 //! \brief Create an event of arbitrary type from its arguments
+//!
+//! This should not be used to load events from JSON - use loadEvent() for that.
+//! \sa loadEvent
 template <typename EventT, typename... ArgTs>
 inline event_ptr_tt<EventT> makeEvent(ArgTs&&... args)
 {
@@ -266,8 +269,6 @@ public:
         return BaseMetaType;
     }
 
-    explicit Event(const QJsonObject& json);
-
     Q_DISABLE_COPY(Event)
     Event(Event&&) noexcept = default;
     Event& operator=(Event&&) = delete;
@@ -364,6 +365,10 @@ public:
     [[deprecated("Use is<CallEvent>() instead")]] bool isCallEvent() const;
 
 protected:
+    friend class EventMetaType<Event>; // To access the below constructor
+
+    explicit Event(const QJsonObject& json);
+
     QJsonObject& editJson() { return _json; }
     virtual void dumpTo(QDebug dbg) const;
 
@@ -427,6 +432,7 @@ public:
 //! pointing to that BaseMetaType.
 //! \sa EventMetaType, EventMetaType::SuppressLoadDerived
 #define QUO_BASE_EVENT(CppType_, ...)                      \
+    friend class EventMetaType<CppType_>;                  \
     static inline EventMetaType<CppType_> BaseMetaType{    \
         #CppType_ __VA_OPT__(,) __VA_ARGS__ };             \
     const AbstractEventMetaType& metaType() const override \
@@ -452,6 +458,7 @@ public:
 //! \sa EventMetaType
 #define QUO_EVENT(CppType_, MatrixType_, ...)                           \
     static inline const auto& TypeId = MatrixType_##_ls;                \
+    friend class EventMetaType<CppType_>;                               \
     static inline const EventMetaType<CppType_> MetaType{               \
         #CppType_, TypeId, BaseMetaType __VA_OPT__(,) __VA_ARGS__       \
     };                                                                  \