text: Implement password hint

A ClutterText in password mode should have the ability to show the last
input character. This feature allows easier password entry on platforms
with unreliable keyboards, such as touchscreens or small devices.

https://bugzilla.gnome.org/show_bug.cgi?id=652588

clutter/clutter-text.c

@@ -188,8 +188,11 @@ struct _ClutterTextPrivate
 
   gunichar password_char;
 
+  guint password_hint_id;
+  guint password_hint_timeout;
+
   /* Signal handler for when the backend changes its font settings */
-  guint font_changed_id;
+  guint settings_changed_id;
 
   /* Signal handler for when the :text-direction changes */
   guint direction_changed_id;
@@ -215,6 +218,8 @@ struct _ClutterTextPrivate
   guint has_focus               : 1;
   guint selected_text_color_set : 1;
   guint paint_volume_valid      : 1;
+  guint show_password_hint      : 1;
+  guint password_hint_visible   : 1;
 };
 
 enum
@@ -267,7 +272,7 @@ enum
 
 static guint text_signals[LAST_SIGNAL] = { 0, };
 
-static void clutter_text_font_changed_cb (ClutterText *text);
+static void clutter_text_settings_changed_cb (ClutterText *text);
 
 static void
 clutter_text_dirty_paint_volume (ClutterText *text)
@@ -362,8 +367,21 @@ clutter_text_get_display_text (ClutterText *self)
       memset (buf, 0, sizeof (buf));
       char_len = g_unichar_to_utf8 (invisible_char, buf);
 
-      for (i = 0; i < priv->n_chars; i++)
+      if (priv->show_password_hint && priv->password_hint_visible)
-        g_string_append_len (str, buf, char_len);
+        {
+          char *last_char;
+
+          for (i = 0; i < priv->n_chars - 1; i++)
+            g_string_append_len (str, buf, char_len);
+
+          last_char = g_utf8_offset_to_pointer (priv->text, priv->n_chars - 1);
+          g_string_append (str, last_char);
+        }
+      else
+        {
+          for (i = 0; i < priv->n_chars; i++)
+            g_string_append_len (str, buf, char_len);
+        }
 
       return g_string_free (str, FALSE);
     }
@@ -557,15 +575,24 @@ clutter_text_set_font_description_internal (ClutterText          *self,
 }
 
 static void
-clutter_text_font_changed_cb (ClutterText *text)
+clutter_text_settings_changed_cb (ClutterText *text)
 {
-  if (text->priv->is_default_font)
+  ClutterTextPrivate *priv = text->priv;
+  guint password_hint_time = 0;
+  ClutterSettings *settings;
+
+  settings = clutter_settings_get_default ();
+
+  g_object_get (settings, "password-hint-time", &password_hint_time, NULL);
+
+  priv->show_password_hint = password_hint_time > 0;
+  priv->password_hint_timeout = password_hint_time;
+
+  if (priv->is_default_font)
     {
       PangoFontDescription *font_desc;
-      ClutterSettings *settings;
       gchar *font_name = NULL;
 
-      settings = clutter_settings_get_default ();
       g_object_get (settings, "font-name", &font_name, NULL);
 
       CLUTTER_NOTE (ACTOR, "Text[%p]: default font changed to '%s'",
@@ -1435,11 +1462,17 @@ clutter_text_dispose (GObject *gobject)
       priv->direction_changed_id = 0;
     }
 
-  if (priv->font_changed_id)
+  if (priv->settings_changed_id)
     {
       g_signal_handler_disconnect (clutter_get_default_backend (),
-                                   priv->font_changed_id);
+                                   priv->settings_changed_id);
-      priv->font_changed_id = 0;
+      priv->settings_changed_id = 0;
+    }
+
+  if (priv->password_hint_id)
+    {
+      g_source_remove (priv->password_hint_id);
+      priv->password_hint_id = 0;
     }
 
   G_OBJECT_CLASS (clutter_text_parent_class)->dispose (gobject);
@@ -1919,6 +1952,20 @@ clutter_text_button_release (ClutterActor       *actor,
   return FALSE;
 }
 
+static gboolean
+clutter_text_remove_password_hint (gpointer data)
+{
+  ClutterText *self = data;
+
+  self->priv->password_hint_visible = FALSE;
+  self->priv->password_hint_id = 0;
+
+  clutter_text_dirty_cache (data);
+  clutter_text_queue_redraw (data);
+
+  return FALSE;
+}
+
 static gboolean
 clutter_text_key_press (ClutterActor    *actor,
                         ClutterKeyEvent *event)
@@ -1976,6 +2023,18 @@ clutter_text_key_press (ClutterActor    *actor,
           clutter_text_delete_selection (self);
           clutter_text_insert_unichar (self, key_unichar);
 
+          if (priv->show_password_hint)
+            {
+              if (priv->password_hint_id != 0)
+                g_source_remove (priv->password_hint_id);
+
+              priv->password_hint_visible = TRUE;
+              priv->password_hint_id =
+                g_timeout_add (priv->password_hint_timeout,
+                               clutter_text_remove_password_hint,
+                               self);
+            }
+
           return TRUE;
         }
     }
@@ -3573,7 +3632,7 @@ clutter_text_init (ClutterText *self)
   ClutterSettings *settings;
   ClutterTextPrivate *priv;
   gchar *font_name;
-  int i;
+  int i, password_hint_time;
 
   self->priv = priv = CLUTTER_TEXT_GET_PRIVATE (self);
 
@@ -3605,7 +3664,10 @@ clutter_text_init (ClutterText *self)
    * the Text and we don't need notifications and sanity checks
    */
   settings = clutter_settings_get_default ();
-  g_object_get (settings, "font-name", &font_name, NULL);
+  g_object_get (settings,
+                "font-name", &font_name,
+                "password-hint-time", &password_hint_time,
+                NULL);
 
   priv->font_name = font_name; /* font_name is allocated */
   priv->font_desc = pango_font_description_from_string (font_name);
@@ -3625,6 +3687,8 @@ clutter_text_init (ClutterText *self)
   priv->preedit_set = FALSE;
 
   priv->password_char = 0;
+  priv->show_password_hint = password_hint_time > 0;
+  priv->password_hint_timeout = password_hint_time;
 
   priv->max_length = 0;
 
@@ -3633,10 +3697,10 @@ clutter_text_init (ClutterText *self)
   priv->cursor_size = DEFAULT_CURSOR_SIZE;
   memset (&priv->cursor_pos, 0, sizeof (ClutterGeometry));
 
-  priv->font_changed_id =
+  priv->settings_changed_id =
     g_signal_connect_swapped (clutter_get_default_backend (),
                               "settings-changed",
-                              G_CALLBACK (clutter_text_font_changed_cb),
+                              G_CALLBACK (clutter_text_settings_changed_cb),
                               self);
 
   priv->direction_changed_id =