diff --git a/callback.c b/callback.c
index 97e76fb..5720a7b 100644
--- a/callback.c
+++ b/callback.c
@@ -6,23 +6,57 @@
 #include "contain.h"
 #include "texts.h"
 
-void activate (GtkApplication *self, gpointer user_data) {
+/******************************************************************************/
+/*    W I N D O W    (H E A D E R   B A R   &   T W O   N O T E B O O K S )   */
+/******************************************************************************/
+void activate (GtkApplication *self, gpointer user_data)
+{
   GtkWindow *window = GTK_WINDOW (gtk_application_window_new (self));
-  window_bar (window, "E coli   (with permission from David S. Goodsell, 2009)");
+  window_header_bar (window, "E coli   (with permission from David S. Goodsell, 2009)");
   two_notebooks_in_two_panes (window);
   gtk_window_present (GTK_WINDOW (window));
 }
 
+/******************************************************************************/
+/*                             B U T T O N S                                  */
+/******************************************************************************/
 void ui_toggle_run_edit (GtkWidget *btt_run_xor_edit, gpointer   data)
 {
-    printf("window.ui_toggle_run_edit()   >>>    mode = %d", get_run_edit_mode ());
-    if (get_run_edit_mode()) {
-          gtk_button_set_icon_name (GTK_BUTTON (btt_run_xor_edit), "system-run-symbolic");
-          set_run_edit_mode (0);
-    } else {
-          gtk_button_set_icon_name (GTK_BUTTON (btt_run_xor_edit), "document-edit-symbolic");
-          set_run_edit_mode (1);
-    }
-    printf(" > %d\n", get_run_edit_mode ());
+  printf("window.ui_toggle_run_edit()   >>>    mode = %d", get_run_edit_mode ());
+  if (get_run_edit_mode()) {
+    gtk_button_set_icon_name (GTK_BUTTON (btt_run_xor_edit), "system-run-symbolic");
+    set_run_edit_mode (0);
+  } else {
+    gtk_button_set_icon_name (GTK_BUTTON (btt_run_xor_edit), "document-edit-symbolic");
+    set_run_edit_mode (1);
+  }
+  printf(" > %d\n", get_run_edit_mode ());
+}
+
+/******************************************************************************/
+/*                                T R E E                                     */
+/******************************************************************************/
+void on_user_tree_expander_toggled(GtkExpander *expander, gpointer user_data)
+{
+  // This is a conceptual callback for when an expander is toggled
+  GtkTreeListRow *row = GTK_TREE_LIST_ROW (user_data);
+  gboolean is_expanded = gtk_tree_list_row_get_expanded(row);
+  gtk_tree_list_row_set_expanded (row, !is_expanded);
+}
+
+void on_bind_user_tree_factory (GtkSignalListItemFactory *factory, GObject* object, gpointer user_data)
+{
+  GtkListItem *list_item = GTK_LIST_ITEM (object); assert (list_item);
+  GtkTreeListRow *row = gtk_list_item_get_item (list_item); assert (row);
+//    if (row != NULL) {
+  const gchar *text = gtk_string_object_get_string (GTK_STRING_OBJECT (gtk_tree_list_row_get_item (row)));
+  GtkWidget *expander = gtk_list_item_get_child (list_item);
+  gtk_expander_set_label (GTK_EXPANDER (expander), text);
+  g_signal_handlers_disconnect_by_func(expander, G_CALLBACK (on_user_tree_expander_toggled), row);
+  g_signal_connect(expander, "activate", G_CALLBACK (on_user_tree_expander_toggled), row);
+  gtk_widget_set_margin_start(expander, gtk_tree_list_row_get_depth(row)*20);
+  gboolean is_expanded = gtk_tree_list_row_get_expanded(row);
+  if (0) printf("[on_bind_user_tree_factory] row content is [%s] and expander is [%d]\n", text, is_expanded);
+//    } else if (0) printf("[on_bind_user_tree_factory] row == NULL\n");
 }
 
diff --git a/callback.d b/callback.d
new file mode 100644
index 0000000..3913f5b
--- /dev/null
+++ b/callback.d
@@ -0,0 +1,3 @@
+callback.o: callback.c hot.h \
+ /gnu/store/fkmpkdav2zmz1k72989bdgpdrfac7rz1-glib-2.78.0/include/glib-2.0/glib.h \
+ display.h contain.h texts.h
diff --git a/callback.h b/callback.h
index 9f6395d..68f462a 100644
--- a/callback.h
+++ b/callback.h
@@ -53,3 +53,5 @@ static const GActionEntry app_actions[] = {
     { "toastclose",     on_toast_close_action,    NULL, NULL, NULL },
 };
 
+void on_user_tree_expander_toggled(GtkExpander *expander, gpointer user_data);
+void on_bind_user_tree_factory (GtkSignalListItemFactory *factory, GObject* object, gpointer user_data);
diff --git a/callback.o b/callback.o
new file mode 100644
index 0000000..79de046
Binary files /dev/null and b/callback.o differ
diff --git a/contain.c b/contain.c
index b2c5206..cbd9f51 100644
--- a/contain.c
+++ b/contain.c
@@ -259,7 +259,7 @@ static void icons_for_fun (GtkHeaderBar *header_bar)
   gtk_header_bar_pack_end (header_bar, GTK_WIDGET (power_low));
 }
 
-void window_bar (GtkWindow *window, char *title){
+void window_header_bar (GtkWindow *window, char *title){
   GtkWidget *header_bar = GTK_WIDGET (gtk_header_bar_new());
   gtk_window_set_titlebar (window, header_bar);
 
diff --git a/contain.d b/contain.d
new file mode 100644
index 0000000..dc2d395
--- /dev/null
+++ b/contain.d
@@ -0,0 +1,3 @@
+contain.o: contain.c hot.h \
+ /gnu/store/fkmpkdav2zmz1k72989bdgpdrfac7rz1-glib-2.78.0/include/glib-2.0/glib.h \
+ display.h contain.h texts.h callback.h
diff --git a/contain.h b/contain.h
index 71c6939..4e7e9d7 100644
--- a/contain.h
+++ b/contain.h
@@ -28,6 +28,7 @@ MyApplication *my_application_new (const char *application_id, GApplicationFlags
 G_END_DECLS
 */
 
+void window_header_bar (GtkWindow *window, char *title);
 void two_notebooks_in_two_panes (GtkWindow *window);
 GtkWidget *get_selected_rules_vpaned_new();
 GtkFrame *get_frame_with_label();
diff --git a/contain.o b/contain.o
new file mode 100644
index 0000000..41e73b9
Binary files /dev/null and b/contain.o differ
diff --git a/display.d b/display.d
new file mode 100644
index 0000000..a8ba66f
--- /dev/null
+++ b/display.d
@@ -0,0 +1,3 @@
+display.o: display.c hot.h \
+ /gnu/store/fkmpkdav2zmz1k72989bdgpdrfac7rz1-glib-2.78.0/include/glib-2.0/glib.h \
+ display.h contain.h texts.h
diff --git a/display.o b/display.o
new file mode 100644
index 0000000..c707579
Binary files /dev/null and b/display.o differ
diff --git a/hot.c b/hot.c
index fc6bce2..f7f257b 100644
--- a/hot.c
+++ b/hot.c
@@ -5,6 +5,7 @@
 
 #include "contain.h"
 #include "texts.h"
+#include "callback.h"
 
 //  https://docs.gtk.org/gtk4/visual_index.html  <  widgets gallery
 //  https://docs.gtk.org/gtk4/section-text-widget.html
@@ -17,6 +18,7 @@ void set_run_edit_mode(int prescribed_mode) {run_edit_mode_val = prescribed_mode
 int  get_run_edit_mode () {return run_edit_mode_val;}
 
 struct TreeNode_t {gchar *text; struct TreeNode_t *child, *next;};
+
 static void add_child_node (struct TreeNode_t *parent, struct TreeNode_t *child){
     if (parent->child) {
         struct TreeNode_t *cur = parent->child;
@@ -64,29 +66,6 @@ static void let_us_create_a_complex_useless_and_expensive_tree (struct TreeNode_
     struct TreeNode_t *cc   = create_user_tree_node("access");        add_child_node(c, cc);
 }
 
-void on_user_tree_expander_toggled(GtkExpander *expander, gpointer user_data)
-{
-    // This is a conceptual callback for when an expander is toggled
-    GtkTreeListRow *row = GTK_TREE_LIST_ROW (user_data);
-    gboolean is_expanded = gtk_tree_list_row_get_expanded(row);
-    gtk_tree_list_row_set_expanded (row, !is_expanded);
-}
-
-static void on_bind_user_tree_factory (GtkSignalListItemFactory *factory, GObject* object, gpointer user_data){
-    GtkListItem *list_item = GTK_LIST_ITEM (object); assert (list_item);
-    GtkTreeListRow *row = gtk_list_item_get_item (list_item); assert (row);
-//    if (row != NULL) {
-        const gchar *text = gtk_string_object_get_string (GTK_STRING_OBJECT (gtk_tree_list_row_get_item (row)));
-        GtkWidget *expander = gtk_list_item_get_child (list_item);
-        gtk_expander_set_label (GTK_EXPANDER (expander), text);
-        g_signal_handlers_disconnect_by_func(expander, G_CALLBACK (on_user_tree_expander_toggled), row);
-        g_signal_connect(expander, "activate", G_CALLBACK (on_user_tree_expander_toggled), row);
-        gtk_widget_set_margin_start(expander, gtk_tree_list_row_get_depth(row)*20);
-        gboolean is_expanded = gtk_tree_list_row_get_expanded(row);
-        if (0) printf("[on_bind_user_tree_factory] row content is [%s] and expander is [%d]\n", text, is_expanded);
-//    } else if (0) printf("[on_bind_user_tree_factory] row == NULL\n");
-}
-
 void on_setup_user_tree_factory (GtkSignalListItemFactory *factory,
                                  GObject* object, gpointer user_data){
     GtkWidget* expander = gtk_expander_new (NULL);
@@ -124,38 +103,38 @@ GListModel* get_user_tree_model (GObject *item, gpointer root){
     return get_user_tree_model_child (cur);
 }
 
-GtkScrolledWindow *get_user_rules_tree (){
-    struct TreeNode_t *tree_root   = create_user_tree_node("root");
-    let_us_create_a_complex_useless_and_expensive_tree (tree_root);
+GtkScrolledWindow *get_user_rules_tree ()
+{
+  struct TreeNode_t *tree_root = create_user_tree_node("root");
+  let_us_create_a_complex_useless_and_expensive_tree (tree_root);
 
-    GtkStringList *model = gtk_string_list_new(NULL);
-    gtk_string_list_append (model, tree_root->text);
-    GtkSignalListItemFactory *factory = GTK_SIGNAL_LIST_ITEM_FACTORY (gtk_signal_list_item_factory_new());
-    g_signal_connect (factory, "setup", G_CALLBACK(on_setup_user_tree_factory), NULL);
-    g_signal_connect (factory, "bind", G_CALLBACK(on_bind_user_tree_factory), NULL);
+  GtkStringList *model = gtk_string_list_new(NULL);
+  gtk_string_list_append (model, tree_root->text);
+  GtkSignalListItemFactory *factory = GTK_SIGNAL_LIST_ITEM_FACTORY (gtk_signal_list_item_factory_new());
+  g_signal_connect (factory, "setup", G_CALLBACK(on_setup_user_tree_factory), NULL);
+  g_signal_connect (factory, "bind", G_CALLBACK(on_bind_user_tree_factory), NULL);
 
-    GtkTreeListModel *tree_model = gtk_tree_list_model_new(
-        G_LIST_MODEL (model),
-        FALSE, // Passthrough - False in actual usage with dynamic children retrieval
-        TRUE, //  FALSE, // autoexpand
-        (GtkTreeListModelCreateModelFunc) &get_user_tree_model,
-        tree_root,
-        NULL // (GDestroyNotify) free_user_tree_node
-    );
+  GtkTreeListModel *tree_model = gtk_tree_list_model_new(
+      G_LIST_MODEL (model),
+      FALSE, // Passthrough - False in actual usage with dynamic children retrieval
+      TRUE, //  FALSE, // autoexpand
+      (GtkTreeListModelCreateModelFunc) &get_user_tree_model,
+      tree_root,
+      NULL // (GDestroyNotify) free_user_tree_node
+  );
 
-    GtkSingleSelection *selection_model = gtk_single_selection_new (G_LIST_MODEL (tree_model));
-    gtk_single_selection_set_autoselect (selection_model, FALSE);
-    gtk_single_selection_set_can_unselect (selection_model, TRUE);
-    GtkWidget *list_view = gtk_list_view_new (GTK_SELECTION_MODEL (selection_model), GTK_LIST_ITEM_FACTORY (factory));
-    GtkScrolledWindow *scrolled_window = GTK_SCROLLED_WINDOW (gtk_scrolled_window_new());
-  // Allocation height too small. Tried to allocate 1922x1030, but GtkNotebook 0x25cd4c0 needs at least 1922x1064.
-  // even if I remove (comment) the next line :
-    gtk_scrolled_window_set_child (scrolled_window, list_view);
-    gtk_scrolled_window_set_policy (scrolled_window, GTK_POLICY_AUTOMATIC, GTK_POLICY_AUTOMATIC);
-    gtk_widget_set_vexpand (GTK_WIDGET (scrolled_window), TRUE);
-    gtk_widget_set_visible (GTK_WIDGET (scrolled_window), TRUE);
-    gtk_widget_set_visible (GTK_WIDGET (list_view), TRUE);
+  GtkSingleSelection *selection_model = gtk_single_selection_new (G_LIST_MODEL (tree_model));
+  gtk_single_selection_set_autoselect (selection_model, FALSE);
+  gtk_single_selection_set_can_unselect (selection_model, TRUE);
+  GtkWidget *list_view = gtk_list_view_new (GTK_SELECTION_MODEL (selection_model), GTK_LIST_ITEM_FACTORY (factory));
+  GtkScrolledWindow *scrolled_window = GTK_SCROLLED_WINDOW (gtk_scrolled_window_new());
+// Allocation height too small. Tried to allocate 1922x1030, but GtkNotebook 0x25cd4c0 needs at least 1922x1064.
+// even if I remove (comment) the next line :
+  gtk_scrolled_window_set_child (scrolled_window, list_view);
+  gtk_scrolled_window_set_policy (scrolled_window, GTK_POLICY_AUTOMATIC, GTK_POLICY_AUTOMATIC);
+  gtk_widget_set_vexpand (GTK_WIDGET (scrolled_window), TRUE);
+  gtk_widget_set_visible (GTK_WIDGET (scrolled_window), TRUE);
+  gtk_widget_set_visible (GTK_WIDGET (list_view), TRUE);
   return scrolled_window;
 }
 
-
diff --git a/hot.d b/hot.d
new file mode 100644
index 0000000..c90269a
--- /dev/null
+++ b/hot.d
@@ -0,0 +1 @@
+hot.o: hot.c contain.h texts.h callback.h
diff --git a/hot.h b/hot.h
index 430f7e3..880cf7b 100644
--- a/hot.h
+++ b/hot.h
@@ -31,8 +31,10 @@
 
 // https://blog.gtk.org/2020/09/08/on-list-models/  <  TODO
 
-
 GtkScrolledWindow *get_user_rules_tree ();
 void set_run_edit_mode(int prescribed_mode);
 int  get_run_edit_mode();
+GListModel* get_user_tree_model (GObject *item, gpointer root);
+void on_setup_user_tree_factory (GtkSignalListItemFactory *factory,
+                                 GObject* object, gpointer user_data);
 
diff --git a/hot.o b/hot.o
new file mode 100644
index 0000000..2bb792f
Binary files /dev/null and b/hot.o differ
diff --git a/junk b/junk
deleted file mode 100644
index e69de29..0000000
diff --git a/main.d b/main.d
new file mode 100644
index 0000000..6c89c45
--- /dev/null
+++ b/main.d
@@ -0,0 +1 @@
+main.o: main.c callback.h
diff --git a/main.o b/main.o
new file mode 100644
index 0000000..9d48ed0
Binary files /dev/null and b/main.o differ
diff --git a/myprogram b/myprogram
new file mode 100755
index 0000000..c186e21
Binary files /dev/null and b/myprogram differ
diff --git a/texts.d b/texts.d
new file mode 100644
index 0000000..18de62c
--- /dev/null
+++ b/texts.d
@@ -0,0 +1 @@
+texts.o: texts.c
diff --git a/texts.o b/texts.o
new file mode 100644
index 0000000..8ea2834
Binary files /dev/null and b/texts.o differ