Locate corner piece in presence of DarkSquares

The 'Rook' move implied by a castling indicated through an obver-sized
King step uses the corner pieces. But the corner isn't necessarily
the edge file if the board is not rectangular, but irregularly shaped
like in Omega Chess. So we have to ignore the DarkSquares, which are
not caounted as belonging to the board.

diff --git a/backend.c b/backend.c
index 454d16b..857dcca 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -9889,7 +9889,7 @@ ParseGameHistory (char *game)
 void
 ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
 {
-  ChessSquare captured = board[toY][toX], piece, king; int p, oldEP = EP_NONE, berolina = 0;
+  ChessSquare captured = board[toY][toX], piece, king; int p, rookX, oldEP = EP_NONE, berolina = 0;
   int promoRank = gameInfo.variant == VariantMakruk || gameInfo.variant == VariantGrand || gameInfo.variant == VariantChuChess ? 3 : 1;
 
     /* [HGM] compute & store e.p. status and castling rights for new position */
@@ -10010,15 +10010,17 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
         && toY == fromY && toX > fromX+1) {
        board[fromY][fromX] = EmptySquare;
         board[toY][toX] = king;
-        board[toY][toX-1] = board[fromY][BOARD_RGHT-1];
-        board[fromY][BOARD_RGHT-1] = EmptySquare;
+       for(rookX=BOARD_RGHT-1; board[toY][rookX] == DarkSquare && rookX > toX + 1; rookX--);
+        board[toY][toX-1] = board[fromY][rookX];
+        board[fromY][rookX] = EmptySquare;
     } else if (board[fromY][fromX] == king
         && fromX != BOARD_LEFT && fromX != BOARD_RGHT-1 // [HGM] cylinder */
                && toY == fromY && toX < fromX-1) {
        board[fromY][fromX] = EmptySquare;
         board[toY][toX] = king;
-        board[toY][toX+1] = board[fromY][BOARD_LEFT];
-        board[fromY][BOARD_LEFT] = EmptySquare;
+       for(rookX=BOARD_LEFT; board[toY][rookX] == DarkSquare && rookX < toX - 1; rookX++);
+        board[toY][toX+1] = board[fromY][rookX];
+        board[fromY][rookX] = EmptySquare;
     } else if ((board[fromY][fromX] == WhitePawn && gameInfo.variant != VariantXiangqi ||
                 board[fromY][fromX] == WhiteLance && gameInfo.variant != VariantSuper && gameInfo.variant != VariantChu)
                && toY >= BOARD_HEIGHT-promoRank && promoChar // defaulting to Q is done elsewhere
@@ -10057,15 +10059,17 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
                && toY == fromY && toX > fromX+1) {
        board[fromY][fromX] = EmptySquare;
         board[toY][toX] = king;
-        board[toY][toX-1] = board[fromY][BOARD_RGHT-1];
-        board[fromY][BOARD_RGHT-1] = EmptySquare;
+       for(rookX=BOARD_RGHT-1; board[toY][rookX] == DarkSquare && rookX > toX + 1; rookX--);
+        board[toY][toX-1] = board[fromY][rookX];
+        board[fromY][rookX] = EmptySquare;
     } else if (board[fromY][fromX] == king
         && fromX != BOARD_LEFT && fromX != BOARD_RGHT-1 // [HGM] cylinder */
                && toY == fromY && toX < fromX-1) {
        board[fromY][fromX] = EmptySquare;
         board[toY][toX] = king;
-        board[toY][toX+1] = board[fromY][BOARD_LEFT];
-        board[fromY][BOARD_LEFT] = EmptySquare;
+       for(rookX=BOARD_LEFT; board[toY][rookX] == DarkSquare && rookX < toX - 1; rookX++);
+        board[toY][toX+1] = board[fromY][rookX];
+        board[fromY][rookX] = EmptySquare;
     } else if (fromY == 7 && fromX == 3
               && board[fromY][fromX] == BlackKing
               && toY == 7 && toX == 5) {