[gnome-chess] gnome-chess currently disables undo functionality when a game has ended. This commit keeps the undo

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 0ab9614e13f3df1c5ca24b6e83474bac7b616a38
Author: Amandeep Singh <newtodisworld gmail com>
Date:   Wed Oct 14 13:20:34 2020 +0530

    gnome-chess currently disables undo functionality when a game has ended.
    This commit keeps the undo button enabled even after end of a game.
    User can now undo a move even after a checkmate or a draw.
    
    Closes #44

 lib/chess-game.vala        | 11 ++++++++++-
 src/chess-engine-cecp.vala |  5 -----
 src/gnome-chess.vala       | 16 ++++------------
 3 files changed, 14 insertions(+), 18 deletions(-)
---
diff --git a/lib/chess-game.vala b/lib/chess-game.vala
index 528c9f5..d962238 100644
--- a/lib/chess-game.vala
+++ b/lib/chess-game.vala
@@ -216,8 +216,17 @@ public class ChessGame : Object
         if (move_stack.next == null)
             return;
 
-        /* Pop off the move state and notify */
+        /* Pop off the move state */
         move_stack.remove_link (move_stack);
+
+        /* Restart the game if undo was done after end of the game */
+        if (result != ChessResult.IN_PROGRESS)
+        {
+            result = ChessResult.IN_PROGRESS;
+            start ();
+        }
+
+        /* Notify */
         undo ();
     }
 
diff --git a/src/chess-engine-cecp.vala b/src/chess-engine-cecp.vala
index fe032c9..4e9b5b0 100644
--- a/src/chess-engine-cecp.vala
+++ b/src/chess-engine-cecp.vala
@@ -78,11 +78,6 @@ public class ChessEngineCECP : ChessEngine
                 stop ();
                 error ();
             }
-            else if (line.has_prefix ("1-0") || line.has_prefix ("0-1"))
-            {
-                /* The engine thinks the game is over and will not play on. */
-                stop ();
-            }
             else if (line == "game is a draw" ||
                      line == "draw" ||
                      line == "Draw" ||
diff --git a/src/gnome-chess.vala b/src/gnome-chess.vala
index 3e6cbfe..ca586e9 100644
--- a/src/gnome-chess.vala
+++ b/src/gnome-chess.vala
@@ -1163,6 +1163,7 @@ Copyright © 2015–2016 Sahil Sareen""";
 
         /* Remove from the PGN game */
         pgn_game.moves.remove_link (pgn_game.moves.last ());
+        pgn_game.result = PGNGame.RESULT_IN_PROGRESS;
 
         /* Remove from the history */
         var model = (Gtk.ListStore) history_combo.model;
@@ -1255,6 +1256,7 @@ Copyright © 2015–2016 Sahil Sareen""";
                 /* Window title on Black's turn if Black is a computer */
                 headerbar.set_title (_("Black is Thinking…"));
         }
+        headerbar.set_subtitle (null);
     }
 
     private void update_pause_resume_button ()
@@ -1281,7 +1283,6 @@ Copyright © 2015–2016 Sahil Sareen""";
     private void game_end_cb ()
     {
         disable_window_action (RESIGN_ACTION_NAME);
-        disable_window_action (UNDO_MOVE_ACTION_NAME);
         disable_window_action (PAUSE_RESUME_ACTION_NAME);
 
         /* In case of engine desync before the first move, or after undo */
@@ -1289,9 +1290,6 @@ Copyright © 2015–2016 Sahil Sareen""";
 
         game_needs_saving = false;
 
-        if (opponent_engine != null)
-            opponent_engine.stop ();
-
         string title = "";
         switch (game.result)
         {
@@ -1502,15 +1500,12 @@ Copyright © 2015–2016 Sahil Sareen""";
 
         var response = dialog.run ();
         dialog.destroy ();
+        game.unpause ();
 
         if (response == ResponseType.ACCEPT)
         {
             game.current_player.claim_draw ();
         }
-        else
-        {
-            game.unpause ();
-        }
     }
 
     public void new_game_cb ()
@@ -1540,6 +1535,7 @@ Copyright © 2015–2016 Sahil Sareen""";
 
         var response = dialog.run ();
         dialog.destroy ();
+        game.unpause ();
 
         if (response == ResponseType.ACCEPT)
         {
@@ -1548,10 +1544,6 @@ Copyright © 2015–2016 Sahil Sareen""";
             else
                 game.current_player.resign ();
         }
-        else
-        {
-            game.unpause ();
-        }
     }
 
     public void undo_move_cb ()