From a360a8beeeff933c8517413eace57a144362df65 Mon Sep 17 00:00:00 2001
From: H.G.Muller <hgm@hgm-xboard.(none)>
Date: Mon, 21 Mar 2016 12:25:02 +0100
Subject: [PATCH] Repair flashing of moved piece (XB)

The flashing was not working (at least in GTK), because the redraw of
the square needed even processing to show something. So the draw/erase
loop that does the flashing needs to call DoEvents() to make things
visible. This however could lead to recursive processing of LeftClick,
as the press of a click-click move already enters the move and starts
the flashing, so that the release usually comes before the press
processing has finished. Which would cause it to be interpreted as
a second move identical to the first. A static flag inside LeftClick
now makes it ignore clicks during flashing, which is just what we had
to do with the release anyway. Flashing should be suppressed during
sweep-selection under-promotion.
---
 backend.c |    9 +++++++--
 board.c   |    8 ++++++--
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/backend.c b/backend.c
index 5a1780d..9b81c39 100644
--- a/backend.c
+++ b/backend.c
@@ -7525,11 +7525,13 @@ LeftClick (ClickType clickType, int xPix, int yPix)
 {
     int x, y;
     Boolean saveAnimate;
-    static int second = 0, promotionChoice = 0, clearFlag = 0, sweepSelecting = 0;
+    static int second = 0, promotionChoice = 0, clearFlag = 0, sweepSelecting = 0, flashing = 0, saveFlash;
     char promoChoice = NULLCHAR;
     ChessSquare piece;
     static TimeMark lastClickTime, prevClickTime;
 
+    if(flashing) return;
+
     x = EventToSquare(xPix, BOARD_WIDTH);
     y = EventToSquare(yPix, BOARD_HEIGHT);
     if (!flipView && y >= 0) {
@@ -7788,6 +7790,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
 	    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
+	    saveFlash = appData.flashCount; appData.flashCount = 0;
 	    Sweep(0); // Pawn that is going to promote: preview promotion piece
 	    sweepSelecting = 1;
 	    DisplayMessage("", _("Pull pawn backwards to under-promote"));
@@ -7804,7 +7807,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
 	MarkTargetSquares(1);
     } 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;
+        *promoRestrict = 0; appData.flashCount = saveFlash;
 	if (appData.animate || appData.highlightLastMove) {
 	    SetHighlights(fromX, fromY, toX, toY);
 	} else {
@@ -7898,6 +7901,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
 	PromotionPopUp(promoChoice);
     } else {
 	int oldMove = currentMove;
+	flashing = 1; // prevent recursive calling (by release of to-click) while flashing piece
 	UserMoveEvent(fromX, fromY, toX, toY, promoChoice);
 	if (!appData.highlightLastMove || gotPremove) ClearHighlights();
 	if (gotPremove) SetPremoveHighlights(fromX, fromY, toX, toY);
@@ -7905,6 +7909,7 @@ LeftClick (ClickType clickType, int xPix, int yPix)
 	   Explode(boards[currentMove-1], fromX, fromY, toX, toY))
 	    DrawPosition(TRUE, boards[currentMove]);
 	fromX = fromY = -1;
+	flashing = 0;
     }
     appData.animate = saveAnimate;
     if (appData.animate || appData.animateDragging) {
diff --git a/board.c b/board.c
index cb6ae94..000af83 100644
--- a/board.c
+++ b/board.c
@@ -821,9 +821,11 @@ DrawSquare (int row, int column, ChessSquare piece, int do_flash)
 	for (i=0; i<appData.flashCount; ++i) {
 	    DrawOneSquare(x, y, piece, square_color, 0, tString, bString, 0);
 	    GraphExpose(currBoard, x, y, squareSize, squareSize);
+	    DoEvents(); // requires event processing to actually update screen :-(
 	    FlashDelay(flash_delay);
 	    DrawOneSquare(x, y, EmptySquare, square_color, 0, tString, bString, 0);
 	    GraphExpose(currBoard, x, y, squareSize, squareSize);
+	    DoEvents();
 	    FlashDelay(flash_delay);
 	}
     }
@@ -950,8 +952,10 @@ DrawPosition (int repaint, Board board)
 	/* Special check for castling so we don't flash both the king
 	   and the rook (just flash the king). */
 	if (do_flash) {
-	    /* Mark rook for drawing with NO flashing. */
-	    check_castle_draw(board, lastBoard[nr], &rrow, &rcol);
+	    if(check_castle_draw(board, lastBoard[nr], &rrow, &rcol)) {
+		/* Mark rook for drawing with NO flashing. */
+		damage[nr][rrow][rcol] |= 1;
+	    }
 	}
 
 	/* First pass -- Erase arrow and grid highlights, but keep square content unchanged. Except for new markers. */
-- 
1.7.0.4