Refactor the event processing code to add ProcessEventLocally().

This new method can be used to only process the event in this handler or any
handlers connected to it (unlike ProcessEventHere() which doesn't follow the
chain at all), without propagating the event upwards (unlike ProcessEvent()).

Unfortunately implementing this required a field to wxEvent but there doesn't
seem to be any other way to do what we need.

There should be no user-visible changes after this commit, it just paves the
way for the upcoming fixes.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64261 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/event.h

@@ -996,6 +996,11 @@ public:
         return false;
     }
 
+    // This is also used only internally by ProcessEvent() to check if it
+    // should process the event normally or only restrict the search for the
+    // event handler to this object itself.
+    bool ShouldProcessHereOnly() const { return m_processHereOnly; }
+
 protected:
     wxObject*         m_eventObject;
     wxEventType       m_eventType;
@@ -1020,6 +1025,11 @@ protected:
     // once for this event
     bool m_wasProcessed;
 
+    // this flag is used by ProcessEventLocally() to prevent ProcessEvent()
+    // from doing its usual stuff and force it to just call ProcessEventHere()
+    // instead, see the comment there explaining why is this needed
+    bool m_processHereOnly;
+
 protected:
     wxEvent(const wxEvent&);            // for implementing Clone()
     wxEvent& operator=(const wxEvent&); // for derived classes operator=()
@@ -1028,6 +1038,10 @@ private:
     // it needs to access our m_propagationLevel
     friend class WXDLLIMPEXP_FWD_BASE wxPropagateOnce;
 
+    // and this one needs to access our m_processHereOnly
+    friend class WXDLLIMPEXP_FWD_BASE wxEventProcessHereOnly;
+
+
     DECLARE_ABSTRACT_CLASS(wxEvent)
 };
 
@@ -1079,6 +1093,32 @@ private:
     wxDECLARE_NO_COPY_CLASS(wxPropagateOnce);
 };
 
+// A helper used by ProcessEventLocally() to restrict the event processing
+// to this handler only.
+class WXDLLIMPEXP_BASE wxEventProcessHereOnly
+{
+public:
+    wxEventProcessHereOnly(wxEvent& event) : m_event(event)
+    {
+        // This would be unexpected and would also restore the wrong value in
+        // this class dtor so if even does happen legitimately we'd need to
+        // store the value in ctor and restore it in dtor.
+        wxASSERT_MSG( !m_event.m_processHereOnly,
+                      "shouldn't be used twice for the same event" );
+
+        m_event.m_processHereOnly = true;
+    }
+
+    ~wxEventProcessHereOnly()
+    {
+        m_event.m_processHereOnly = false;
+    }
+
+private:
+    wxEvent& m_event;
+
+    wxDECLARE_NO_COPY_CLASS(wxEventProcessHereOnly);
+};
 
 #if wxUSE_GUI
 
@@ -2966,6 +3006,20 @@ public:
     bool SafelyProcessEvent(wxEvent& event);
         // NOTE: uses ProcessEvent()
 
+    // This method tries to process the event in this event handler, including
+    // any preprocessing done by TryBefore() and all the handlers chained to
+    // it, but excluding the post-processing done in TryAfter().
+    //
+    // It is meant to be called from ProcessEvent() only and is not virtual,
+    // additional event handlers can be hooked into the normal event processing
+    // logic using TryBefore() and TryAfter() hooks.
+    //
+    // You can also call it yourself to forward an event to another handler but
+    // without propagating it upwards if it's unhandled (this is usually
+    // unwanted when forwarding as the original handler would already do it if
+    // needed normally).
+    bool ProcessEventLocally(wxEvent& event);
+
     // Schedule the given event to be processed later. It takes ownership of
     // the event pointer, i.e. it will be deleted later. This is safe to call
     // from multiple threads although you still need to ensure that wxString
@@ -3180,9 +3234,8 @@ public:
 
     // The method tries to process the event in this event handler.
     //
-    // It is meant to be called from ProcessEvent() only and is not virtual,
-    // additional event handlers can be hooked into the normal event processing
-    // logic using TryBefore() and TryAfter() hooks.
+    // It is called from ProcessEventLocally() and normally shouldn't be called
+    // directly as doing it would ignore any chained event handlers.
     bool ProcessEventHere(wxEvent& event);
 
 
@@ -3274,6 +3327,9 @@ private:
     // pass the event to wxTheApp instance, called from TryAfter()
     bool DoTryApp(wxEvent& event);
 
+    // try to process events in all handlers chained to this one
+    bool DoTryChain(wxEvent& event);
+
     DECLARE_DYNAMIC_CLASS_NO_COPY(wxEvtHandler)
 };