[gnome-control-center] user-accounts: Introduce an empty state page

[Felipe Borges <felipeborges src gnome org>]

commit a701b4646c213a784ca0066a9681ac9f06287b9f
Author: Felipe Borges <felipeborges gnome org>
Date:   Wed Feb 22 12:18:24 2017 +0100

    user-accounts: Introduce an empty state page
    
    There are eventually corner cases where there's no user other than
    root in the system and control-center can be launched by the root
    user (not recommended). In this cases, the panel crashes without
    any user to show (since accountsservice would just list normal
    users).
    
    This patch introduces an empty state[0] "No Users Page".
    
    [0] https://wiki.gnome.org/Design/OS/EmptyStates
    
    https://bugzilla.gnome.org/show_bug.cgi?id=773673

 panels/user-accounts/data/user-accounts-dialog.ui |   48 +++++++++++++++++++++
 panels/user-accounts/um-user-panel.c              |   17 +++++++-
 2 files changed, 64 insertions(+), 1 deletions(-)
---
diff --git a/panels/user-accounts/data/user-accounts-dialog.ui 
b/panels/user-accounts/data/user-accounts-dialog.ui
index cdd4951..a2c11b1 100644
--- a/panels/user-accounts/data/user-accounts-dialog.ui
+++ b/panels/user-accounts/data/user-accounts-dialog.ui
@@ -42,6 +42,11 @@
       <column type="gchararray"/>
     </columns>
   </object>
+
+  <object class="GtkStack" id="stack">
+    <property name="visible">True</property>
+    <property name="visible-child">empty-state</property>
+    <child>
       <object class="GtkOverlay" id="overlay">
         <property name="visible">True</property>
         <child type="overlay">
@@ -435,6 +440,49 @@
           </object>
         </child>
       </object>
+      <packing>
+        <property name="name">_users</property>
+      </packing>
+    </child>
+    <child>
+      <object class="GtkBox" id="empty-state">
+        <property name="visible">True</property>
+        <property name="orientation">GTK_ORIENTATION_VERTICAL</property>
+        <property name="valign">GTK_ALIGN_CENTER</property>
+        <property name="spacing">12</property>
+        <style>
+          <class name="dim-label"/>
+        </style>
+        <child>
+          <object class="GtkImage">
+            <property name="visible">True</property>
+            <property name="icon_name">avatar-default-symbolic</property>
+            <property name="pixel_size">192</property>
+          </object>
+        </child>
+        <child>
+          <object class="GtkLabel">
+            <property name="visible">True</property>
+            <property name="label" translatable="yes" comments="Translators: This is the empty state page 
label which states that there are no users to show in the panel.">No Users Found</property>
+            <attributes>
+              <attribute name="weight" value="bold"/>
+              <attribute name="scale" value="1.6"/>
+            </attributes>
+          </object>
+        </child>
+        <child>
+          <object class="GtkLabel">
+            <property name="visible">True</property>
+            <property name="label" translatable="yes">Unlock to add a user account.</property>
+          </object>
+        </child>
+      </object>
+      <packing>
+        <property name="name">_empty_state</property>
+      </packing>
+    </child>
+  </object>
+
   <object class="GtkSizeGroup" id="user-icon-sizegroup">
     <property name="mode">both</property>
     <widgets>
diff --git a/panels/user-accounts/um-user-panel.c b/panels/user-accounts/um-user-panel.c
index c1875cb..cb60625 100644
--- a/panels/user-accounts/um-user-panel.c
+++ b/panels/user-accounts/um-user-panel.c
@@ -71,6 +71,7 @@ struct _CcUserPanelPrivate {
         GSettings *login_screen_settings;
 
         GtkWidget *headerbar_buttons;
+        GtkWidget *stack;
         GtkWidget *main_box;
         UmCarousel *carousel;
         ActUser *selected_user;
@@ -92,9 +93,14 @@ get_widget (CcUserPanelPrivate *d, const char *name)
         return (GtkWidget *)gtk_builder_get_object (d->builder, name);
 }
 
+/* Headerbar button states. */
 #define PAGE_LOCK "_lock"
 #define PAGE_ADDUSER "_adduser"
 
+/* Panel states */
+#define PAGE_NO_USERS "_empty_state"
+#define PAGE_USERS "_users"
+
 static void show_restart_notification (CcUserPanelPrivate *d, const gchar *locale);
 static gint user_compare (gconstpointer i, gconstpointer u);
 
@@ -273,6 +279,7 @@ reload_users (CcUserPanelPrivate *d, ActUser *selected_user)
         UmCarouselItem *item;
         GtkSettings *settings;
         gboolean animations;
+        gboolean can_reload;
 
         settings = gtk_settings_get_default ();
 
@@ -286,6 +293,13 @@ reload_users (CcUserPanelPrivate *d, ActUser *selected_user)
         list = act_user_manager_list_users (d->um);
         g_debug ("Got %d users\n", g_slist_length (list));
 
+        can_reload = (list != NULL);
+        gtk_stack_set_visible_child_name (GTK_STACK (d->stack),
+                                          can_reload ? PAGE_USERS : PAGE_NO_USERS);
+
+        if (!can_reload)
+            return;
+
         list = g_slist_sort (list, (GCompareFunc) sort_users);
         for (l = list; l; l = l->next) {
                 user = l->data;
@@ -1478,13 +1492,14 @@ cc_user_panel_init (CcUserPanel *self)
         g_object_unref (provider);
 
         d->headerbar_buttons = get_widget (d, "headerbar-buttons");
+        d->stack = get_widget (d, "stack");
         d->login_screen_settings = settings_or_null ("org.gnome.login-screen");
 
         d->password_dialog = um_password_dialog_new ();
         button = get_widget (d, "user-icon-button");
         d->photo_dialog = um_photo_dialog_new (button);
         d->main_box = get_widget (d, "accounts-vbox");
-        gtk_container_add (GTK_CONTAINER (self), get_widget (d, "overlay"));
+        gtk_container_add (GTK_CONTAINER (self), d->stack);
         d->history_dialog = um_history_dialog_new ();
         setup_main_window (self);
 }