fix for bug #8847: moving backward while examining on FICS not reported to engine

I moved Daniel's code that backs up the engine when a bord with a lower number is received to a place where it is always done in zippy mode, rather than only when the engine is analyzing.

Apart from taking back moves, there was also the case where the
user moves forward by more than one move (usually immediately to
end-of-game). In this case a new movelist is fetched from the ICS
to recover the moves that were skipped. But this assumes that the
engine is at the start of the game and feeds all these moves to the
engine. So the engine had to be reset in this case to stay in sync.

diff --git a/backend.c b/backend.c
index 860a160..c6eedec 100755 (executable)
--- a/backend.c
+++ b/backend.c
@@ -3720,15 +3720,6 @@ ParseBoard12(string)
     /* Update currentMove and known move number limits */
     newMove = newGame || moveNum > forwardMostMove;
 
-    /* [DM] If we found takebacks during icsEngineAnalyze try send to engine */
-    if (!newGame && appData.icsEngineAnalyze && moveNum < forwardMostMove) {
-        takeback = forwardMostMove - moveNum;
-        for (i = 0; i < takeback; i++) {
-             if (appData.debugMode) fprintf(debugFP, "take back move\n");
-             SendToProgram("undo\n", &first);
-        }
-    }
-
     if (newGame) {
        forwardMostMove = backwardMostMove = currentMove = moveNum;
        if (gameMode == IcsExamining && moveNum == 0) {
@@ -3741,6 +3732,20 @@ ParseBoard12(string)
        }
     } else if (moveNum == forwardMostMove + 1 || moveNum == forwardMostMove
               || (moveNum < forwardMostMove && moveNum >= backwardMostMove)) {
+#if ZIPPY
+       /* [DM] If we found takebacks during icsEngineAnalyze try send to engine */
+       /* [HGM] applied this also to an engine that is silently watching        */
+       if (appData.zippyPlay && moveNum < forwardMostMove && first.initDone &&
+           (gameMode == IcsObserving || gameMode == IcsExamining) &&
+           gameInfo.variant == currentlyInitializedVariant) {
+         takeback = forwardMostMove - moveNum;
+         for (i = 0; i < takeback; i++) {
+           if (appData.debugMode) fprintf(debugFP, "take back move\n");
+           SendToProgram("undo\n", &first);
+         }
+       }
+#endif
+
        forwardMostMove = moveNum;
        if (!pausing || currentMove > forwardMostMove)
          currentMove = forwardMostMove;
@@ -3751,12 +3756,20 @@ ParseBoard12(string)
            forwardMostMove = pauseExamForwardMostMove;
            return;
        }
-       forwardMostMove = backwardMostMove = currentMove = moveNum;
        if (gameMode == IcsExamining && moveNum > 0 && appData.getMoveList) {
+#if ZIPPY
+           if(appData.zippyPlay && forwardMostMove > 0 && first.initDone) {
+               // [HGM] when we will receive the move list we now request, it will be
+               // fed to the engine from the first move on. So if the engine is not
+               // in the initial position now, bring it there.
+               InitChessProgram(&first, 0);
+           }
+#endif
            ics_getting_history = H_REQUESTED;
            sprintf(str, "%smoves %d\n", ics_prefix, gamenum);
            SendToICS(str);
        }
+       forwardMostMove = backwardMostMove = currentMove = moveNum;
     }
     
     /* Update the clocks */