diff --git a/gtk_treeview_example b/gtk_treeview_example
index 4163322..a124d1a 100755
Binary files a/gtk_treeview_example and b/gtk_treeview_example differ
diff --git a/main.c b/main.c
index 2ae58cc..d0e7192 100644
--- a/main.c
+++ b/main.c
@@ -12,6 +12,8 @@
 #include <glib-2.0/glib.h>
 #include <gtk-4.0/gtk/gtk.h>
 
+#define verb 0
+
 // Simplified TreeNode structure for demonstration purposes
 struct TreeNode_t
 {
@@ -48,7 +50,7 @@ void add_child_node (struct TreeNode_t *parent, struct TreeNode_t *child)
     }
 }
 
-static insert_data()    //  (TreeNode_t *root)
+static void insert_data  (struct TreeNode_t  *root)
 {
     struct TreeNode_t *A = create_tree_node("A");    add_child_node(root, A);
     struct TreeNode_t *B = create_tree_node("B");    add_child_node(A, B);
@@ -89,7 +91,7 @@ GListModel* get_children_model (struct TreeNode_t *parent)
     GtkStringList *list = NULL;
     
     if (parent) {
-        printf("[get_children_model] here is %s content : ", parent->text);
+        if (verb) printf("[get_children_model] here is %s content : ", parent->text);
 
         child = parent->child;
 
@@ -98,11 +100,11 @@ GListModel* get_children_model (struct TreeNode_t *parent)
         }
         while(child) {
              gtk_string_list_append(list, child->text);
-             printf("%s ", child->text);
+             if (verb) printf("%s ", child->text);
              child = child->next;
         }
     }
-    printf("\n");
+    if (verb) printf("\n");
 
     return G_LIST_MODEL(list);
 }
@@ -114,11 +116,11 @@ GListModel* create_model_func(GObject *item, gpointer user_data)
     struct TreeNode_t *parent = NULL;
     struct TreeNode_t *res = NULL;
 
-    gchar *string =  gtk_string_object_get_string(GTK_STRING_OBJECT(item));
+    const char* string =  gtk_string_object_get_string(GTK_STRING_OBJECT(item));
     
     parent = root;
     while (cur) {
-        if (strcmp(string, cur->text) == NULL) {
+        if (! strcmp(string, cur->text)) {
             res = cur;
             break;
         }
@@ -130,7 +132,7 @@ GListModel* create_model_func(GObject *item, gpointer user_data)
         }
     }
 
-    printf("[create_model_func] here is %s item\n", string);
+    if (verb) printf("[create_model_func] here is %s item\n", string);
 
     return get_children_model(cur);
 }
@@ -148,7 +150,7 @@ void on_setup_factory (GtkListItemFactory *factory, GtkListItem *list_item, gpoi
 {
     GtkWidget* expander = gtk_expander_new (NULL);
     gtk_list_item_set_child (list_item, expander);
-    printf("[on_setup_factory] here is an expander\n");
+    if (verb) printf("[on_setup_factory] here is an expander\n");
 }
 
 void on_bind_factory (GtkListItemFactory *factory, GtkListItem *list_item, gpointer user_data)
@@ -172,14 +174,14 @@ void on_bind_factory (GtkListItemFactory *factory, GtkListItem *list_item, gpoin
         gboolean is_expanded = gtk_tree_list_row_get_expanded(row);
         //gtk_tree_list_row_set_expanded(row, !is_expanded);
     } else {
-        printf("[on_bind_factory] here is NON %s content\n", text);
+        if (verb) printf("[on_bind_factory] here is NON %s content\n", text);
     }
 }
 
 void on_selection_changed (GtkSelectionModel* self, guint position,
                            guint n_items, gpointer user_data)
 {
-    printf("Cc\n");
+    if (verb) printf("Cc\n");
 }
 
 // Application activation callback
@@ -207,7 +209,7 @@ void app_activate (GApplication *app, gpointer user_data)
         (GDestroyNotify)g_object_unref //(GDestroyNotify)free_tree_node
     );
 
-    GtkSingleSelection *selection_model = gtk_single_selection_new (
+    GtkSingleSelection *selection_model = gtk_single_selection_new ( //  GtkSelectionModel
                                             G_LIST_MODEL (tree_model));
 
     gtk_single_selection_set_autoselect(selection_model, FALSE);
@@ -215,7 +217,7 @@ void app_activate (GApplication *app, gpointer user_data)
     g_signal_connect (selection_model, "selection-changed",
                                         G_CALLBACK(on_selection_changed), NULL);
 
-    GtkWidget *list_view = gtk_list_view_new (selection_model, factory);
+    GtkWidget *list_view = gtk_list_view_new (GTK_SELECTION_MODEL(selection_model), factory);
 
     gtk_window_set_child(GTK_WINDOW(window), list_view);
 
@@ -226,7 +228,7 @@ int main (int argc, char **argv)
 {
     // Create a simple tree structure
     root = create_tree_node("Root");
-    insert_data();
+    insert_data(root);
 
     GtkApplication *app = gtk_application_new("org.gtk.example", G_APPLICATION_FLAGS_NONE);
     g_signal_connect(app, "activate", G_CALLBACK(app_activate), NULL);