shell: Show the submenu icon hint for the applications panel

The panel swarms details/devices/privacy show this icon. Since the applications
panel is not made from sub-panels, this doesn't show. For consistency this shows
the icon so the transition isn't as jarring for the user.

Add a flat into the panel .desktop file to enable this - other panels might
require this in the future

panels/applications/gnome-applications-panel.desktop.in.in

@@ -13,3 +13,4 @@ Categories=GNOME;GTK;Settings;DesktopSettings;X-GNOME-Settings-Panel;X-GNOME-Acc
 OnlyShowIn=GNOME;Unity;
 # Translators: Search terms to find the Privacy panel. Do NOT translate or localize the semicolons! The list MUST also end with a semicolon!
 Keywords=application;flatpak;permission;setting;
+X-GNOME-ControlCenter-HasSidebar=true

shell/cc-panel-list.c

@@ -295,7 +295,8 @@ row_data_new (CcPanelCategory     category,
               const gchar        *description,
               const GStrv         keywords,
               const gchar        *icon,
-              CcPanelVisibility   visibility)
+              CcPanelVisibility   visibility,
+              gboolean            has_sidebar)
 {
   GtkWidget *label, *grid, *image;
   RowData *data;
@@ -343,6 +344,14 @@ row_data_new (CcPanelCategory     category,
   gtk_label_set_max_width_chars (GTK_LABEL (label), 25);
   gtk_label_set_line_wrap (GTK_LABEL (label), TRUE);
 
+  if (has_sidebar)
+    {
+      image = gtk_image_new_from_icon_name ("go-next-symbolic", GTK_ICON_SIZE_BUTTON);
+      gtk_style_context_add_class (gtk_widget_get_style_context (image), "sidebar-icon");
+      gtk_grid_attach (GTK_GRID (grid), image, 2, 0, 1, 1);
+      gtk_widget_show (image);
+    }
+
   gtk_style_context_add_class (gtk_widget_get_style_context (label), "dim-label");
   gtk_grid_attach (GTK_GRID (grid), label, 1, 1, 1, 1);
 
@@ -1017,7 +1026,8 @@ cc_panel_list_add_panel (CcPanelList        *self,
                          const gchar        *description,
                          const GStrv         keywords,
                          const gchar        *icon,
-                         CcPanelVisibility   visibility)
+                         CcPanelVisibility   visibility,
+                         gboolean            has_sidebar)
 {
   GtkWidget *listbox;
   RowData *data, *search_data;
@@ -1025,14 +1035,14 @@ cc_panel_list_add_panel (CcPanelList        *self,
   g_return_if_fail (CC_IS_PANEL_LIST (self));
 
   /* Add the panel to the proper listbox */
-  data = row_data_new (category, id, title, description, keywords, icon, visibility);
+  data = row_data_new (category, id, title, description, keywords, icon, visibility, has_sidebar);
   gtk_widget_set_visible (data->row, visibility == CC_PANEL_VISIBLE);
 
   listbox = get_listbox_from_category (self, category);
   gtk_container_add (GTK_CONTAINER (listbox), data->row);
 
   /* And add to the search listbox too */
-  search_data = row_data_new (category, id, title, description, keywords, icon, visibility);
+  search_data = row_data_new (category, id, title, description, keywords, icon, visibility, has_sidebar);
   gtk_widget_set_visible (search_data->row, visibility != CC_PANEL_HIDDEN);
 
   gtk_container_add (GTK_CONTAINER (self->search_listbox), search_data->row);

shell/cc-panel-list.h

@@ -61,7 +61,8 @@ void                 cc_panel_list_add_panel                     (CcPanelList
                                                                   const gchar        *description,
                                                                   const GStrv         keywords,
                                                                   const gchar        *icon,
-                                                                  CcPanelVisibility   visibility);
+                                                                  CcPanelVisibility   visibility,
+                                                                  gboolean            has_sidebar);
 
 void                 cc_panel_list_set_active_panel               (CcPanelList       *self,
                                                                    const gchar       *id);

shell/cc-shell-model.c

@@ -219,7 +219,7 @@ static void
 cc_shell_model_init (CcShellModel *self)
 {
   GType types[] = {G_TYPE_STRING, G_TYPE_STRING, G_TYPE_APP_INFO, G_TYPE_STRING, G_TYPE_UINT,
-                   G_TYPE_STRING, G_TYPE_STRING, G_TYPE_ICON, G_TYPE_STRV, G_TYPE_UINT };
+                   G_TYPE_STRING, G_TYPE_STRING, G_TYPE_ICON, G_TYPE_STRV, G_TYPE_UINT, G_TYPE_BOOLEAN };
 
   gtk_list_store_set_column_types (GTK_LIST_STORE (self),
                                    N_COLS, types);
@@ -286,11 +286,13 @@ cc_shell_model_add_item (CcShellModel    *model,
   g_auto(GStrv) keywords = NULL;
   g_autofree gchar *casefolded_name = NULL;
   g_autofree gchar *casefolded_description = NULL;
+  gboolean has_sidebar;
 
   casefolded_name = cc_util_normalize_casefold_and_unaccent (name);
   casefolded_description = cc_util_normalize_casefold_and_unaccent (comment);
   keywords = get_casefolded_keywords (appinfo);
   icon = symbolicize_g_icon (g_app_info_get_icon (appinfo));
+  has_sidebar = g_desktop_app_info_get_boolean (G_DESKTOP_APP_INFO (appinfo), "X-GNOME-ControlCenter-HasSidebar");
 
   gtk_list_store_insert_with_values (GTK_LIST_STORE (model), NULL, 0,
                                      COL_NAME, name,
@@ -303,6 +305,7 @@ cc_shell_model_add_item (CcShellModel    *model,
                                      COL_GICON, icon,
                                      COL_KEYWORDS, keywords,
                                      COL_VISIBILITY, CC_PANEL_VISIBLE,
+                                     COL_HAS_SIDEBAR, has_sidebar,
                                      -1);
 }
 

shell/cc-shell-model.h

@@ -54,6 +54,7 @@ enum
   COL_GICON,
   COL_KEYWORDS,
   COL_VISIBILITY,
+  COL_HAS_SIDEBAR,
 
   N_COLS
 };

shell/cc-window.c

@@ -351,6 +351,7 @@ setup_model (CcWindow *self)
       g_autofree gchar *id = NULL;
       g_auto(GStrv) keywords = NULL;
       CcPanelVisibility visibility;
+      gboolean has_sidebar;
       const gchar *icon_name = NULL;
 
       gtk_tree_model_get (model, &iter,
@@ -361,6 +362,7 @@ setup_model (CcWindow *self)
                           COL_NAME, &name,
                           COL_KEYWORDS, &keywords,
                           COL_VISIBILITY, &visibility,
+                          COL_HAS_SIDEBAR, &has_sidebar,
                           -1);
 
       if (G_IS_THEMED_ICON (icon))
@@ -373,7 +375,8 @@ setup_model (CcWindow *self)
                                description,
                                keywords,
                                icon_name,
-                               visibility);
+                               visibility,
+                               has_sidebar);
 
       valid = gtk_tree_model_iter_next (model, &iter);
     }