Implement vetoing editing in wxDataViewTextRenderer under GTK+ and test it in the sample (see also #10495)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@59457 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/dataview/mymodels.cpp

@@ -69,6 +69,15 @@ wxString MyMusicTreeModel::GetTitle( const wxDataViewItem &item ) const
     return node->m_title;
 }
 
+wxString MyMusicTreeModel::GetArtist( const wxDataViewItem &item ) const
+{
+    MyMusicTreeModelNode *node = (MyMusicTreeModelNode*) item.GetID();
+    if (!node)      // happens if item.IsOk()==false
+        return wxEmptyString;
+
+    return node->m_artist;
+}
+
 int MyMusicTreeModel::GetYear( const wxDataViewItem &item ) const
 {
     MyMusicTreeModelNode *node = (MyMusicTreeModelNode*) item.GetID();