Added wxPGProperty::OnValidationFailure(); needed it and some other tweaks to allow vetoing value changes of ComboBox editors

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58047 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/propgrid/props.h

@@ -428,6 +428,8 @@ public:
     // this take advantage of it.
     virtual int GetChoiceSelection() const { return m_index; }
 
+    virtual void OnValidationFailure( wxVariant& pendingValue );
+
 protected:
 
     int GetIndex() const;
@@ -447,6 +449,7 @@ private:
 
     // Relies on ValidateValue being called always before OnSetValue
     static int              ms_nextIndex;
+    static int              ms_prevIndex;
 };
 
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