Fix spurious undo at game start

[xboard.git] / backend.c

diff --git a/backend.c b/backend.c
index 233fb8d..174b2a2 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -8551,7 +8551,7 @@ DeferredBookMove (void)
 
 static int savedWhitePlayer, savedBlackPlayer, pairingReceived;
 static ChessProgramState *stalledEngine;
-static char stashedInputMove[MSG_SIZ];
+static char stashedInputMove[MSG_SIZ], abortEngineThink;
 
 void
 HandleMachineMove (char *message, ChessProgramState *cps)
@@ -8634,24 +8634,27 @@ FakeBookMove: // [HGM] book: we jump here to simulate machine moves after book h
            return;
        }
 
+      if(cps->usePing) {
+
         /* This method is only useful on engines that support ping */
+        if(abortEngineThink) {
+           if (appData.debugMode) {
+               fprintf(debugFP, "Undoing move from aborted think of %s\n", cps->which);
+           }
+            SendToProgram("undo\n", cps);
+           return;
+       }
+
         if (cps->lastPing != cps->lastPong) {
-         if (gameMode == BeginningOfGame) {
            /* Extra move from before last new; ignore */
            if (appData.debugMode) {
                fprintf(debugFP, "Ignoring extra move from %s\n", cps->which);
            }
-         } else {
-           if (appData.debugMode) {
-               fprintf(debugFP, "Undoing extra move from %s, gameMode %d\n",
-                       cps->which, gameMode);
-           }
-
-            SendToProgram("undo\n", cps);
-         }
          return;
        }
 
+      } else {
+
        switch (gameMode) {
          case BeginningOfGame:
            /* Extra move from before last reset; ignore */
@@ -8697,6 +8700,7 @@ FakeBookMove: // [HGM] book: we jump here to simulate machine moves after book h
            }
            return;
        }
+      }
 
         if(cps->alphaRank) AlphaRank(machineMove, 4);
 
@@ -9115,6 +9119,11 @@ FakeBookMove: // [HGM] book: we jump here to simulate machine moves after book h
            }
            initPing = -1;
         }
+       if(cps->lastPing == cps->lastPong && abortEngineThink) {
+           abortEngineThink = FALSE;
+           DisplayMessage("", "");
+           ThawUI();
+       }
        return;
     }
     if(!strncmp(message, "highlight ", 10)) {
@@ -14974,10 +14983,15 @@ EditGameEvent ()
       case MachinePlaysBlack:
       case BeginningOfGame:
        SendToProgram("force\n", &first);
-       if (first.usePing) { // [HGM] always send ping when we might interrupt machine thinking
-         char buf[MSG_SIZ];
-         snprintf(buf, MSG_SIZ, "ping %d\n", initPing = ++first.lastPing);
-         SendToProgram(buf, &first);
+       if(gameMode == (forwardMostMove & 1 ? MachinePlaysBlack : MachinePlaysWhite)) { // engine is thinking
+           if (first.usePing) { // [HGM] always send ping when we might interrupt machine thinking
+               char buf[MSG_SIZ];
+               abortEngineThink = TRUE;
+               snprintf(buf, MSG_SIZ, "ping %d\n", initPing = ++first.lastPing);
+               SendToProgram(buf, &first);
+               DisplayMessage("Aborting engine think", "");
+               FreezeUI();
+           }
        }
        SetUserThinkingEnables();
        break;