list-view: Don't show folder expanders by default.

Disables the > arrows next to folders with content, and disallows
expansion/collapse via those arrows or by keyboard right and left.

ref:
https://github.com/orgs/linuxmint/discussions/564

Author: mtwebster

gresources/nemo-file-management-properties.glade

@@ -914,6 +914,22 @@ along with .  If not, see <http://www.gnu.org/licenses/>.
                                             <property name="position">0</property>
                                           </packing>
                                         </child>
+                                        <child>
+                                          <object class="GtkCheckButton" id="list_view_show_expanders_checkbutton">
+                                            <property name="label" translatable="yes">Show expanders for folders with content</property>
+                                            <property name="visible">True</property>
+                                            <property name="can-focus">True</property>
+                                            <property name="receives-default">False</property>
+                                            <property name="use-underline">True</property>
+                                            <property name="xalign">0</property>
+                                            <property name="draw-indicator">True</property>
+                                          </object>
+                                          <packing>
+                                            <property name="expand">False</property>
+                                            <property name="fill">False</property>
+                                            <property name="position">1</property>
+                                          </packing>
+                                        </child>
                                       </object>
                                     </child>
                                   </object>

libnemo-private/nemo-global-preferences.h

@@ -181,6 +181,7 @@ enum
 #define NEMO_PREFERENCES_LIST_VIEW_DEFAULT_ZOOM_LEVEL		"default-zoom-level"
 #define NEMO_PREFERENCES_LIST_VIEW_DEFAULT_VISIBLE_COLUMNS		"default-visible-columns"
 #define NEMO_PREFERENCES_LIST_VIEW_DEFAULT_COLUMN_ORDER		"default-column-order"
+#define NEMO_PREFERENCES_LIST_VIEW_ENABLE_EXPANSION         "enable-folder-expansion"
 
 #define NEMO_PREFERENCES_MAX_THUMBNAIL_THREADS "thumbnail-threads"
 

libnemo-private/nemo-tree-view-drag-dest.c

@@ -523,7 +523,8 @@ drag_motion_callback (GtkWidget *widget,
 		    gtk_tree_path_compare (old_drop_path, drop_path) != 0)) {
 			remove_expand_timeout (dest);
 		}
-        if (g_settings_get_boolean (nemo_preferences, NEMO_PREFERENCES_EXPAND_ROW_ON_DND_DWELL)) {
+        if (g_settings_get_boolean (nemo_list_view_preferences, NEMO_PREFERENCES_LIST_VIEW_ENABLE_EXPANSION) &&
+            g_settings_get_boolean (nemo_preferences, NEMO_PREFERENCES_EXPAND_ROW_ON_DND_DWELL)) {
             if (dest->details->expand_id == 0 && drop_path != NULL) {
                 gtk_tree_model_get_iter (model, &drop_iter, drop_path);
                 if (gtk_tree_model_iter_has_child (model, &drop_iter)) {

libnemo-private/org.nemo.gschema.xml

@@ -523,6 +523,10 @@
       <summary>Default column order in the list view</summary>
       <description>Default column order in the list view.</description>
     </key>
+    <key name="enable-folder-expansion" type="b">
+      <default>false</default>
+      <summary>If true, allow folders with content to be expanded in the current view.</summary>
+    </key>
   </schema>
 
   <schema id="org.nemo.sidebar-panels" path="/org/nemo/sidebar-panels/" gettext-domain="nemo">

src/nemo-file-management-properties.c

@@ -72,6 +72,7 @@
 #define NEMO_FILE_MANAGEMENT_PROPERTIES_SWAP_TRASH_DELETE "swap_trash_binding_checkbutton"
 #define NEMO_FILE_MANAGEMENT_PROPERTIES_OPEN_NEW_WINDOW_WIDGET "new_window_checkbutton"
 #define NEMO_FILE_MANAGEMENT_PROPERTIES_TREE_VIEW_FOLDERS_WIDGET "treeview_folders_checkbutton"
+#define NEMO_FILE_MANAGEMENT_PROPERTIES_SHOW_LIST_VIEW_EXPANDERS_WIDGET "list_view_show_expanders_checkbutton"
 
 #define NEMO_FILE_MANAGEMENT_PROPERTIES_SHOW_PREVIOUS_ICON_TOOLBAR_WIDGET "show_previous_icon_toolbar_togglebutton"
 #define NEMO_FILE_MANAGEMENT_PROPERTIES_SHOW_NEXT_ICON_TOOLBAR_WIDGET "show_next_icon_toolbar_togglebutton"
@@ -1105,6 +1106,10 @@ nemo_file_management_properties_dialog_setup (GtkBuilder  *builder,
                        NEMO_FILE_MANAGEMENT_PROPERTIES_NEMO_PREFERENCES_EXPAND_ROW_ON_DND_DWELL_WIDGET,
                        NEMO_PREFERENCES_EXPAND_ROW_ON_DND_DWELL);
 
+    bind_builder_bool (builder, nemo_list_view_preferences,
+                       NEMO_FILE_MANAGEMENT_PROPERTIES_SHOW_LIST_VIEW_EXPANDERS_WIDGET,
+                       NEMO_PREFERENCES_LIST_VIEW_ENABLE_EXPANSION);
+
     setup_tooltip_items (builder);
     connect_tooltip_items (builder);
 

src/nemo-list-view.c

@@ -280,6 +280,18 @@ tooltip_prefs_changed_callback (NemoListView *view)
     view->details->tooltip_flags = nemo_global_preferences_get_tooltip_flags ();
 }
 
+static void
+expanders_enabled_changed_cb (NemoListView *view)
+{
+    g_return_if_fail (NEMO_IS_LIST_VIEW (view));
+    g_return_if_fail (GTK_IS_TREE_VIEW (view->details->tree_view) && view->details->tree_view != NULL);
+
+    gtk_tree_view_collapse_all (view->details->tree_view);
+    gtk_tree_view_set_show_expanders (view->details->tree_view,
+                                      g_settings_get_boolean (nemo_list_view_preferences,
+                                                             NEMO_PREFERENCES_LIST_VIEW_ENABLE_EXPANSION));
+}
+
 static void
 list_selection_changed_callback (GtkTreeSelection *selection, gpointer user_data)
 {
@@ -1466,6 +1478,9 @@ key_press_callback (GtkWidget *widget, GdkEventKey *event, gpointer callback_dat
 		}
 		break;
 	case GDK_KEY_Right:
+        if (!g_settings_get_boolean (nemo_list_view_preferences, NEMO_PREFERENCES_LIST_VIEW_ENABLE_EXPANSION))
+            break;
+
 		gtk_tree_view_get_cursor (tree_view, &path, NULL);
 		if (path) {
 			gtk_tree_view_expand_row (tree_view, path, FALSE);
@@ -1474,6 +1489,9 @@ key_press_callback (GtkWidget *widget, GdkEventKey *event, gpointer callback_dat
 		handled = TRUE;
 		break;
 	case GDK_KEY_Left:
+        if (!g_settings_get_boolean (nemo_list_view_preferences, NEMO_PREFERENCES_LIST_VIEW_ENABLE_EXPANSION))
+            break;
+
 		gtk_tree_view_get_cursor (tree_view, &path, NULL);
 		if (path) {
 			if (!gtk_tree_view_collapse_row (tree_view, path)) {
@@ -2503,6 +2521,14 @@ create_and_set_up_tree_view (NemoListView *view)
 
     gtk_tree_view_set_rubber_banding (GTK_TREE_VIEW (view->details->tree_view), TRUE);
 
+    gtk_tree_view_set_show_expanders (view->details->tree_view,
+                                      g_settings_get_boolean (nemo_list_view_preferences,
+                                                              NEMO_PREFERENCES_LIST_VIEW_ENABLE_EXPANSION));
+    g_signal_connect_swapped (nemo_list_view_preferences,
+                              "changed::" NEMO_PREFERENCES_LIST_VIEW_ENABLE_EXPANSION,
+                              G_CALLBACK (expanders_enabled_changed_cb),
+                              view);
+
 	view->details->columns = g_hash_table_new_full (g_str_hash,
 							g_str_equal,
 							(GDestroyNotify) g_free,