Fix gating at Rook on castling in holdingless seirawan

Castling must gate what is under the Rook if there is nothing under
the King. ApplyMove() must know this when it gets a move with gating
suffix, while UserMoveEvent() should be smart enough to add that suffix
when the user castles.

diff --git a/backend.c b/backend.c
index e152081..c0e4139 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -7284,6 +7284,20 @@ UserMoveEvent (int fromX, int fromY, int toX, int toY, int promoChar)
        return;
     }
 
+    if(gameInfo.variant == VariantSChess && !gameInfo.holdingsSize && !promoChar) {
+       int piece, rank, file;
+       switch(moveType) { // detect castlings
+           case WhiteKingSideCastle:  file = BOARD_RGHT-1; rank = 0; break;
+           case WhiteQueenSideCastle: file = BOARD_LEFT;   rank = 0; break;
+           case BlackKingSideCastle:  file = BOARD_RGHT-1; rank = BOARD_HEIGHT-1; break;
+           case BlackQueenSideCastle: file = BOARD_LEFT;   rank = BOARD_HEIGHT-1; break;
+           default: file = -1;
+       }
+       if(file >= 0 && (piece = boards[currentMove][rank][file]) != DarkSquare) { // castling that should have gated at Rook
+           promoChar = ToLower(PieceToChar(piece));
+       }
+    }
+
     FinishMove(moveType, fromX, fromY, toX, toY, promoChar);
 }
 
@@ -10776,9 +10790,15 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
     }
 
     if(gameInfo.variant == VariantSChess && promoChar != NULLCHAR && promoChar != '=' && piece != WhitePawn && piece != BlackPawn) {
-        board[fromY][fromX] = CharToPiece(piece < BlackPawn ? ToUpper(promoChar) : ToLower(promoChar)); // S-Chess gating
-       int white = (piece < BlackPawn);
-       if(!gameInfo.holdingsSize) board[fromY-2*white+1][fromX] = DarkSquare;
+       int file = fromX, white = (piece < BlackPawn);
+       if(!gameInfo.holdingsSize) {
+           int rank = fromY-2*white+1;
+           if(rank >= 0 && rank < BOARD_HEIGHT) {
+               if(board[rank][file] == DarkSquare) file = (toX > fromX ? BOARD_RGHT -1 : BOARD_LEFT); // must be castling
+               board[rank][file] = DarkSquare;
+           }
+       }
+        board[fromY][file] = CharToPiece(piece < BlackPawn ? ToUpper(promoChar) : ToLower(promoChar)); // S-Chess gating
     } else
     if(promoChar == '+') {
         /* [HGM] Shogi-style promotions, to piece implied by original (Might overwrite ordinary Pawn promotion) */