From c31e4039f0f464ea750bf68835c707338f25a90a Mon Sep 17 00:00:00 2001
From: H.G.Muller <hgm@hgm-xboard.(none)>
Date: Wed, 1 Jan 2020 19:56:28 +0100
Subject: [PATCH] Fix promotions in holdingless seirawan

When the extreme ranks are really holdings, promotion should take place on
the penultimate ranks. So a zone width of 2 is now specified in that case.
---
 backend.c |    4 +++-
 moves.c   |    1 +
 2 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/backend.c b/backend.c
index 7c9bcfb..e152081 100644
--- a/backend.c
+++ b/backend.c
@@ -6767,7 +6767,7 @@ HasPromotionChoice (int fromX, int fromY, int toX, int toY, char *promoChoice, i
         if(PieceToChar(piece) != '+' && PieceToChar(CHUPROMOTED(piece)) == '+') highestPromotingPiece = piece;
     } else if(gameInfo.variant == VariantMakruk || gameInfo.variant == VariantGrand || gameInfo.variant == VariantChuChess) {
         promotionZoneSize = 3;
-    }
+    } else if(gameInfo.variant == VariantSChess && !gameInfo.holdingsSize) promotionZoneSize = 2;
 
     // Treat Lance as Pawn when it is not representing Amazon or Lance
     if(gameInfo.variant != VariantSuper && gameInfo.variant != VariantChu) {
@@ -7576,6 +7576,7 @@ CanPromote (ChessSquare piece, int y)
         int zone = (gameInfo.variant == VariantChuChess ? 3 : 1);
 	if(gameMode == EditPosition) return FALSE; // no promotions when editing position
 	// some variants have fixed promotion piece, no promotion at all, or another selection mechanism
+	if(gameInfo.variant == VariantSChess && !gameInfo.holdingsSize) zone = 2;
 	if(IS_SHOGI(gameInfo.variant)          || gameInfo.variant == VariantXiangqi ||
 	   gameInfo.variant == VariantSuper    || gameInfo.variant == VariantGreat   ||
 	  (gameInfo.variant == VariantShatranj || gameInfo.variant == VariantCourier ||
@@ -10428,6 +10429,7 @@ ApplyMove (int fromX, int fromY, int toX, int toY, int promoChar, Board board)
     /* we can always do that 'in place', now pointers to these rights are passed to ApplyMove */
 
       if(gameInfo.variant == VariantBerolina) berolina = EP_BEROLIN_A;
+      if(gameInfo.variant == VariantSChess && !gameInfo.holdingsSize) promoRank = 2;
       oldEP = (signed char)board[EP_STATUS]; epRank = board[EP_RANK]; epFile = board[EP_FILE]; lastFile = board[LAST_TO] & 255,lastRank = board[LAST_TO] >> 8;
       board[EP_STATUS] = EP_NONE;
       board[EP_FILE] = board[EP_RANK] = 100, board[LAST_TO] = toX + 256*toY;
diff --git a/moves.c b/moves.c
index 50a049b..5c708cd 100644
--- a/moves.c
+++ b/moves.c
@@ -759,6 +759,7 @@ GenPseudoLegal (Board board, int flags, MoveCallback callback, VOIDSTAR closure,
     int epfile = (signed char)board[EP_STATUS]; // [HGM] gamestate: extract ep status from board
     int promoRank = gameInfo.variant == VariantMakruk || gameInfo.variant == VariantGrand || gameInfo.variant == VariantChuChess ? 3 : 1;
 
+    if(gameInfo.variant == VariantSChess && !gameInfo.holdingsSize) promoRank = 2;
     for (rf = 0; rf < BOARD_HEIGHT; rf++)
       for (ff = BOARD_LEFT; ff < BOARD_RGHT; ff++) {
           ChessSquare piece;
-- 
1.7.0.4