[gnome-taquin] Update title on back.

[Arnaud B. <arnaudb src gnome org>]

commit 68dbe330a256502d8f471d8244b6cc62fed5f9e1
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Thu Dec 5 23:57:01 2019 +0100

    Update title on back.

 src/game-window.vala |  2 +-
 src/taquin-main.vala | 22 +++++++++++++++++-----
 2 files changed, 18 insertions(+), 6 deletions(-)
---
diff --git a/src/game-window.vala b/src/game-window.vala
index fcae467..5e4c430 100644
--- a/src/game-window.vala
+++ b/src/game-window.vala
@@ -132,7 +132,7 @@ private class GameWindow : BaseWindow, AdaptativeWidget
         back ();
     }
 
-    internal void set_title (string game_name)
+    internal void update_title (string game_name)
     {
         headerbar.update_title (game_name);
     }
diff --git a/src/taquin-main.vala b/src/taquin-main.vala
index 3d60cd3..2481f0c 100644
--- a/src/taquin-main.vala
+++ b/src/taquin-main.vala
@@ -199,6 +199,7 @@ private class Taquin : Gtk.Application, BaseApplication
                                  null,  // appearance menu
                                  night_light_monitor);
         window.play.connect (start_game);
+        window.back.connect (back_cb);
         window.undo.connect (undo_cb);
         window.restart.connect (restart_cb);
 
@@ -316,11 +317,7 @@ private class Taquin : Gtk.Application, BaseApplication
         GameType type = (GameType) settings.get_enum ("type");
         int8 size = (int8) settings.get_int ("size"); /* 2 <= size <= 9 */
         game = new Game (type, size);
-        /* Translators: name of one of the games, as displayed in the headerbar when playing */
-        window.set_title (type == GameType.FIFTEEN ? _("15-Puzzle")
-
-        /* Translators: name of one of the games, as displayed in the headerbar when playing */
-                                                   : _("16-Puzzle"));
+        set_window_title (type == GameType.FIFTEEN);
         view.game = (!) game;
         window.move_done (0);
         move_done = false;
@@ -342,6 +339,15 @@ private class Taquin : Gtk.Application, BaseApplication
         ((!) game).move.connect (move_cb);
     }
 
+    private void set_window_title (bool fifteen)
+    {
+        /* Translators: name of one of the games, as displayed in the headerbar when playing */
+        window.update_title (fifteen ? _("15-Puzzle")
+
+        /* Translators: name of one of the games, as displayed in the headerbar when playing */
+                                     : _("16-Puzzle"));
+    }
+
     /*\
     * * Signals from window
     \*/
@@ -354,6 +360,12 @@ private class Taquin : Gtk.Application, BaseApplication
         move_done = false;
     }
 
+    private void back_cb ()
+        requires (game != null)
+    {
+        set_window_title (((!) game).game_type == GameType.FIFTEEN);
+    }
+
     private void undo_cb ()
         requires (game != null)
     {