From b7bf5d068c672d4356bc94711364c03e3d83d6e9 Mon Sep 17 00:00:00 2001
From: H.G.Muller <hgm@hgm-xboard.(none)>
Date: Sun, 6 Mar 2016 23:52:06 +0100
Subject: [PATCH] Fix spurious clearing of Engine Output during PV walk

Due to messing with forwardMostMove during PV walking the Engine Output
panes couldbe cleared when a new PV arrived.
---
 engineoutput.c |    4 ++--
 engineoutput.h |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/engineoutput.c b/engineoutput.c
index 2d0bd06..4e00960 100644
--- a/engineoutput.c
+++ b/engineoutput.c
@@ -222,7 +222,7 @@ SetProgramStats (FrontEndProgramStats * stats) // now directly called by back-en
         clearMemo = TRUE;
     }
 
-    if( lastForwardMostMove[which] != forwardMostMove ) {
+    if( lastForwardMostMove[which] != forwardMostMove && endPV < 0) {
         clearMemo = TRUE;
     }
 
@@ -257,7 +257,7 @@ SetProgramStats (FrontEndProgramStats * stats) // now directly called by back-en
 
     /* Update */
     lastDepth[which] = depth == 1 && ed.nodes == 0 ? 0 : depth; // [HGM] info-line kudge
-    lastForwardMostMove[which] = forwardMostMove;
+    if(endPV < 0) lastForwardMostMove[which] = forwardMostMove; // not during PV walk!
 
     UpdateControls( &ed );
 }
diff --git a/engineoutput.h b/engineoutput.h
index b3015a5..21bb6d1 100644
--- a/engineoutput.h
+++ b/engineoutput.h
@@ -56,7 +56,7 @@ enum ENGINE_STATE { STATE_UNKNOWN, STATE_THINKING, STATE_IDLE, STATE_PONDERING,
 
 extern int  windowMode;
 extern char exclusionHeader[];
-extern int highTextStart[2], highTextEnd[2];
+extern int highTextStart[2], highTextEnd[2], endPV;
 
 // back-end called by front-end
 void SetEngineState( int which, enum ENGINE_STATE state, char * state_data );
-- 
1.7.0.4