Implement 'choice' engine->GUI command

A new CECP command is implemented: With 'choice XYZ' in reply to a
'lift' or 'put' command an engine can redefine the promotion choice
of the promotion move that emitted these to X, Y or Z. (Always capitals!)
For now only affects sweep & detour promotions, not the promotion
popup.

diff --git a/backend.c b/backend.c
index e5a79a3..8831176 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -443,6 +443,7 @@ char *currentDebugFile; // [HGM] debug split: to remember name
 char cmailMove[CMAIL_MAX_GAMES][MOVE_LEN], cmailMsg[MSG_SIZ];
 char bookOutput[MSG_SIZ*10], thinkOutput[MSG_SIZ*10], lastHint[MSG_SIZ];
 char thinkOutput1[MSG_SIZ*10];
+char promoRestrict[MSG_SIZ];
 
 ChessProgramState first, second, pairing;
 
@@ -5408,8 +5409,10 @@ Sweep (int step)
        else if(promoSweep == BlackPawn && step < 0 && !toggleFlag) promoSweep = WhitePawn;
        else if(promoSweep == WhiteKing && step > 0 && !toggleFlag) promoSweep = BlackKing;
        if(!step) step = -1;
-    } while(PieceToChar(promoSweep) == '.' || PieceToChar(promoSweep) == '~' || promoSweep == pawn ||
+    } while(PieceToChar(promoSweep) == '.' || PieceToChar(promoSweep) == '~' ||
            !toggleFlag && PieceToChar(promoSweep) == '+' || // skip promoted versions of other
+           promoRestrict[0] ? !strchr(promoRestrict, ToUpper(PieceToChar(promoSweep))) : // if choice set available, use it 
+           promoSweep == pawn ||
            appData.testLegality && (promoSweep == king || gameInfo.variant != VariantChuChess &&
             (promoSweep == WhiteLion || promoSweep == BlackLion)));
     if(toX >= 0) {
@@ -7564,7 +7567,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
                DragPieceBegin(xPix, yPix, FALSE); dragging = 1;
                if(appData.sweepSelect && CanPromote(piece = boards[currentMove][fromY][fromX], fromY)) {
                    promoSweep = defaultPromoChoice;
-                   selectFlag = 0; lastX = xPix; lastY = yPix;
+                   selectFlag = 0; lastX = xPix; lastY = yPix; *promoRestrict = 0;
                    Sweep(0); // Pawn that is going to promote: preview promotion piece
                    DisplayMessage("", _("Pull pawn backwards to under-promote"));
                }
@@ -7629,7 +7632,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
                DragPieceBegin(xPix, yPix, FALSE);
                if(appData.sweepSelect && CanPromote(piece = boards[currentMove][y][x], y)) {
                    promoSweep = defaultPromoChoice;
-                   selectFlag = 0; lastX = xPix; lastY = yPix;
+                   selectFlag = 0; lastX = xPix; lastY = yPix; *promoRestrict = 0;
                    Sweep(0); // Pawn that is going to promote: preview promotion piece
                }
            }
@@ -7717,6 +7720,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
            promoSweep = defaultPromoChoice;
            if(gameInfo.variant != VariantChuChess && PieceToChar(CHUPROMOTED piece) == '+') promoSweep = CHUPROMOTED piece;
            selectFlag = 0; lastX = xPix; lastY = yPix;
+           ReportClick("put", x, y); // extra put to prompt engine for 'choice' command
            Sweep(0); // Pawn that is going to promote: preview promotion piece
            sweepSelecting = 1;
            DisplayMessage("", _("Pull pawn backwards to under-promote"));
@@ -7732,6 +7736,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
        }
     } else if(sweepSelecting) { // this must be the up-click corresponding to the down-click that started the sweep
        sweepSelecting = 0; appData.animate = FALSE; // do not animate, a selected piece already on to-square
+        *promoRestrict = 0;
        if (appData.animate || appData.highlightLastMove) {
            SetHighlights(fromX, fromY, toX, toY);
        } else {
@@ -9040,6 +9045,11 @@ FakeBookMove: // [HGM] book: we jump here to simulate machine moves after book h
       }
       return;
     }
+    if(sscanf(message, "choice %s", promoRestrict) == 1 && promoSweep != EmptySquare) {
+      promoSweep = PieceToChar(forwardMostMove&1 ? ToLower(*promoRestrict) : ToUpper(*promoRestrict));
+      Sweep(0);
+      return;
+    }
     /* [HGM] Allow engine to set up a position. Don't ask me why one would
      * want this, I was asked to put it in, and obliged.
      */