From: H.G.Muller <hgm@hgm-xboard.(none)>
Date: Sun, 2 Nov 2014 14:31:34 +0000 (+0100)
Subject: Implement non-royal castling
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=3808a80498c0347b4ad4c52c4c1d7e93bcf57c1f;p=xboard.git

Implement non-royal castling

The Betza move generator allows castlings to be specified on non-royal
pieces, and indeed the Omega-Chess 'guarding' castles Q with R. To
prevent ambiguity this is implemented as a two-leg move QxR-s (with 's'
the target square specified in the O atom). This automatically takes care
of removal of the 'Rook', so that in ApplyMove() we only have to put it
back on the proper side of the 'King'.
---

diff --git a/backend.c b/backend.c
index 3e432ae..dd8bbb1 100644
--- a/backend.c
+++ b/backend.c
@@ -7501,6 +7501,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
 	toP = boards[currentMove][y][x];
 	frc = appData.fischerCastling || gameInfo.variant == VariantSChess;
  	if( (killX < 0 || x != fromX || y != fromY) && // [HGM] lion: do not interpret igui as deselect!
+	    legal[y][x] == 0 && // if engine told we can move to here, do it even if own piece
 	   ((WhitePawn <= fromP && fromP <= WhiteKing &&
 	     WhitePawn <= toP && toP <= WhiteKing &&
 	     !(fromP == WhiteKing && toP == WhiteRook && frc) &&
@@ -9889,7 +9890,7 @@ 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, rookX, oldEP = EP_NONE, berolina = 0;
+  ChessSquare captured = board[toY][toX], piece, king, killed; 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 */
@@ -9913,6 +9914,7 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
 
       if( killX >= 0 && killY >= 0 ) // [HGM] lion: Lion trampled over something
 //           victim = board[killY][killX],
+           killed = board[killY][killX],
            board[killY][killX] = EmptySquare,
            board[EP_STATUS] = EP_CAPTURE;
 
@@ -9984,6 +9986,12 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
      if(gameInfo.variant == VariantKnightmate)
          king += (int) WhiteUnicorn - (int) WhiteKing;
 
+    if(piece != WhiteKing && piece != BlackKing && pieceDesc[piece] && killX >= 0 && strchr(pieceDesc[piece], 'O') // Betza castling-enabled
+       && (piece < BlackPawn ? killed < BlackPawn : killed >= BlackPawn)) {    // and captures own
+	board[toY][toX] = piece; board[fromY][fromX] = EmptySquare;
+	board[toY][toX + (killX < fromX ? 1 : -1)] = killed;
+        board[EP_STATUS] = EP_NONE; // capture was fake!
+    } else
     /* Code added by Tord: */
     /* FRC castling assumed when king captures friendly rook. [HGM] or RxK for S-Chess */
     if (board[fromY][fromX] == WhiteKing && board[toY][toX] == WhiteRook ||
diff --git a/moves.c b/moves.c
index b4edc45..dbc8f41 100644
--- a/moves.c
+++ b/moves.c
@@ -433,10 +433,20 @@ MovesFromString (Board board, int flags, int f, int r, int tx, int ty, int angle
 		if(mode & 1024) {            // castling
 		    i = 2;                   // kludge to elongate move indefinitely
 		    if(occup == 4) continue; // skip empty squares
-		    if((x == BOARD_LEFT || vx < 0 && board[y][x-1] == DarkSquare)  && board[y][x] == initialPosition[y][x]) // reached initial corner piece
+		    if((x == BOARD_LEFT || vx < 0 && board[y][x-1] == DarkSquare)  && board[y][x] == initialPosition[y][x]) { // reached initial corner piece
+		      if(pc != WhiteKing && pc != BlackKing) { // non-royal castling (to be entered as two-leg move via 'Rook')
+			if(killX < 0) cb(board, flags, FirstLeg,   r, f, y, x, cl);
+			legNr <<= 1;  cb(board, flags, NormalMove, r, f, y, f - expo, cl); legNr >>= 1;
+		      } else
 			cb(board, flags, mine == 1 ? WhiteQueenSideCastle : BlackQueenSideCastle, r, f, y, f - expo, cl);
-		    if((x == BOARD_RGHT-1 || vx > 0 && board[y][x+1] == DarkSquare) && board[y][x] == initialPosition[y][x])
+		    }
+		    if((x == BOARD_RGHT-1 || vx > 0 && board[y][x+1] == DarkSquare) && board[y][x] == initialPosition[y][x]) {
+		      if(pc != WhiteKing && pc != BlackKing) {
+			if(killX < 0) cb(board, flags, FirstLeg,   r, f, y, x, cl);
+			legNr <<= 1;  cb(board, flags, NormalMove, r, f, y, f + expo, cl); legNr >>= 1;
+		      } else
 			cb(board, flags, mine == 1 ? WhiteKingSideCastle : BlackKingSideCastle, r, f, y, f + expo, cl);
+		    }
 		    break;
 		}
 		if(mode & 16 && (board[y][x] == WhiteKing || board[y][x] == BlackKing)) break; // tame piece, cannot capture royal