Allow definition of castling in piece command

Castling is defined by the O atom, with a suffix indicating the number
of steps the King must step in the direction of the corner. Kings keep
their normal castling unless overruled by this. Can currently only be
used on the variant's royal piece, as XBoard's ApplyMove() is not smart
enough to understand displacing the corner piece is implied when it is
used on other pieces.

diff --git a/moves.c b/moves.c
index 9700dbf..e3afe36 100644 (file)
--- a/moves.c
+++ b/moves.c
@@ -256,6 +256,9 @@ MovesFromString (Board board, int flags, int f, int r, char *desc, MoveCallback
        if(expo > 9) p++;                             // allow double-digit
        desc = p;                                     // this is start of next move
        if(initial && board[r][f] != initialPosition[r][f]) continue;
+       if(expo > 1 && dx == 0 && dy == 0) {          // castling indicated by O + number
+           mode |= 16; dy = 1;
+       }
         do {
          for(dir=0, bit=1; dir<8; dir++, bit += bit) { // loop over directions
            int i = expo, vx, vy;
@@ -274,6 +277,15 @@ MovesFromString (Board board, int flags, int f, int r, char *desc, MoveCallback
                if(mode & 8 && y == board[EP_RANK] && occup == 4 && board[EP_FILE] == x) { // to e.p. square
                    cb(board, flags, mine == 1 ? WhiteCapturesEnPassant : BlackCapturesEnPassant, r, f, y, x, cl);
                }
+               if(mode & 16) {              // castling
+                   i = 2;                   // kludge to elongate move indefinitely
+                   if(occup == 4) continue; // skip empty squares
+                   if(x == BOARD_LEFT   && board[y][x] == initialPosition[y][x]) // reached initial corner piece
+                       cb(board, flags, mine == 1 ? WhiteQueenSideCastle : BlackQueenSideCastle, r, f, y, f - expo, cl);
+                   if(x == BOARD_RGHT-1 && board[y][x] == initialPosition[y][x])
+                       cb(board, flags, mine == 1 ? WhiteKingSideCastle : BlackKingSideCastle, r, f, y, f + expo, cl);
+                   break;
+               }
                if(occup & mode) cb(board, flags, NormalMove, r, f, y, x, cl); // allowed, generate
                if(occup != 4) break; // not valid transit square
            } while(--i);
@@ -1218,6 +1230,7 @@ GenLegal (Board board, int  flags, MoveCallback callback, VOIDSTAR closure, Ches
     int ignoreCheck = (flags & F_IGNORE_CHECK) != 0;
     ChessSquare wKing = WhiteKing, bKing = BlackKing, *castlingRights = board[CASTLING];
     int inCheck = !ignoreCheck && CheckTest(board, flags, -1, -1, -1, -1, FALSE); // kludge alert: this would mark pre-existing checkers if status==1
+    char *p;
 
     cl.cb = callback;
     cl.cl = closure;
@@ -1232,6 +1245,9 @@ GenLegal (Board board, int  flags, MoveCallback callback, VOIDSTAR closure, Ches
         wKing = WhiteUnicorn; bKing = BlackUnicorn;
     }
 
+    p = (flags & F_WHITE_ON_MOVE ? pieceDesc[wKing] : pieceDesc[bKing]);
+    if(p && strchr(p, 'O')) return FALSE; // [HGM] gen: castlings were already generated from string
+
     for (ff = BOARD_WIDTH>>1; ff >= (BOARD_WIDTH-1)>>1; ff-- /*ics wild 1*/) {
        if ((flags & F_WHITE_ON_MOVE) &&
            (flags & F_WHITE_KCASTLE_OK) &&