Fix PV walking in analysis mode

ParsePV assumed that the PV would always have been produced by an engin
thinking about the final position of the game (or the one before it). In
analysismode, however, the engine can be analysing positions internal to
the game, and the PV would be considered invalid. This is fixed by
cutting of the tail off the game (shelving it in variation fashion)
before starting the PV walk, and reverting afterwards.
  For this the PushTail and PopTail routines had to be split into an
'inner' part, doing the pushing and popping, and an outer part, handling
menu graying and popdowns (which is undesirable in in this application).

diff --git a/backend.c b/backend.c
index 466809b..6101165 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -506,6 +506,8 @@ ChessMove savedResult[MAX_VARIATIONS];
 
 void PushTail P((int firstMove, int lastMove));
 Boolean PopTail P((Boolean annotate));
+void PushInner P((int firstMove, int lastMove));
+void PopInner P((Boolean annotate));
 void CleanupTail P((void));
 
 ChessSquare  FIDEArray[2][BOARD_FILES] = {
@@ -5221,6 +5223,7 @@ ParseOneMove(move, moveNum, moveType, fromX, fromY, toX, toY, promoChar)
     }
 }
 
+Boolean pushed = FALSE;
 
 void
 ParsePV(char *pv, Boolean storeComments)
@@ -5230,6 +5233,10 @@ ParsePV(char *pv, Boolean storeComments)
   Boolean valid;
   int nr = 0;
 
+  if (gameMode == AnalyzeMode && currentMove < forwardMostMove) {
+    PushInner(currentMove, forwardMostMove); // [HGM] engine might not be thinking on forwardMost position!
+    pushed = TRUE;
+  }
   endPV = forwardMostMove;
   do {
     while(*pv == ' ' || *pv == '\n' || *pv == '\t') pv++; // must still read away whitespace
@@ -5326,6 +5333,7 @@ UnLoadPV()
   if(endPV < 0) return;
   endPV = -1;
   currentMove = forwardMostMove;
+  if(pushed) { PopInner(0); pushed = FALSE; } // restore shelved game contnuation
   ClearPremoveHighlights();
   DrawPosition(TRUE, boards[currentMove]);
 }
@@ -16059,16 +16067,10 @@ int wrap(char *dest, char *src, int count, int width, int *lp)
 // [HGM] vari: routines for shelving variations
 
 void
-PushTail(int firstMove, int lastMove)
+PushInner(int firstMove, int lastMove)
 {
        int i, j, nrMoves = lastMove - firstMove;
 
-       if(appData.icsActive) { // only in local mode
-               forwardMostMove = currentMove; // mimic old ICS behavior
-               return;
-       }
-       if(storedGames >= MAX_VARIATIONS-1) return;
-
        // push current tail of game on stack
        savedResult[storedGames] = gameInfo.result;
        savedDetails[storedGames] = gameInfo.resultDetails;
@@ -16093,19 +16095,27 @@ PushTail(int firstMove, int lastMove)
 
        storedGames++;
        forwardMostMove = firstMove; // truncate game so we can start variation
+}
+
+void
+PushTail(int firstMove, int lastMove)
+{
+       if(appData.icsActive) { // only in local mode
+               forwardMostMove = currentMove; // mimic old ICS behavior
+               return;
+       }
+       if(storedGames >= MAX_VARIATIONS-2) return; // leave one for PV-walk
+
+       PushInner(firstMove, lastMove);
        if(storedGames == 1) GreyRevert(FALSE);
 }
 
-Boolean
-PopTail(Boolean annotate)
+void
+PopInner(Boolean annotate)
 {
        int i, j, nrMoves;
        char buf[8000], moveBuf[20];
 
-       if(appData.icsActive) return FALSE; // only in local mode
-       if(!storedGames) return FALSE; // sanity
-       CommentPopDown(); // make sure no stale variation comments to the destroyed line can remain open
-
        storedGames--;
        ToNrEvent(savedFirst[storedGames]); // sets currentMove
        nrMoves = savedLast[storedGames] - currentMove;
@@ -16145,6 +16155,17 @@ PopTail(Boolean annotate)
       }
        gameInfo.resultDetails = savedDetails[storedGames];
        forwardMostMove = currentMove + nrMoves;
+}
+
+Boolean
+PopTail(Boolean annotate)
+{
+       if(appData.icsActive) return FALSE; // only in local mode
+       if(!storedGames) return FALSE; // sanity
+       CommentPopDown(); // make sure no stale variation comments to the destroyed line can remain open
+
+       PopInner(annotate);
+
        if(storedGames == 0) GreyRevert(TRUE);
        return TRUE;
 }