Alter treatment of moves with empty squares

[xboard.git] / backend.c

diff --git a/backend.c b/backend.c
index b1df197..1165932 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -6445,7 +6445,7 @@ void LeftClick(ClickType clickType, int xPix, int yPix)
 {
     int x, y;
     Boolean saveAnimate;
-    static int second = 0, promotionChoice = 0;
+    static int second = 0, promotionChoice = 0, clearFlag = 0;
     char promoChoice = NULLCHAR;
     ChessSquare piece;
 
@@ -6602,6 +6602,14 @@ void LeftClick(ClickType clickType, int xPix, int yPix)
 
     if (clickType == Release && x == fromX && y == fromY) {
        DragPieceEnd(xPix, yPix); dragging = 0;
+       if(clearFlag) {
+           // a deferred attempt to click-click move an empty square on top of a piece
+           boards[currentMove][y][x] = EmptySquare;
+           ClearHighlights();
+           DrawPosition(FALSE, boards[currentMove]);
+           fromX = fromY = -1; clearFlag = 0;
+           return;
+       }
        if (appData.animateDragging) {
            /* Undo animation damage if any */
            DrawPosition(FALSE, NULL);
@@ -6621,12 +6629,20 @@ void LeftClick(ClickType clickType, int xPix, int yPix)
        return;
     }
 
+    clearFlag = 0;
+
     /* we now have a different from- and (possibly off-board) to-square */
     /* Completed move */
     toX = x;
     toY = y;
     saveAnimate = appData.animate;
     if (clickType == Press) {
+       if(gameMode == EditPosition && boards[currentMove][fromY][fromX] == EmptySquare) {
+           // must be Edit Position mode with empty-square selected
+           fromX = x; fromY = y; DragPieceBegin(xPix, yPix); dragging = 1; // consider this a new attempt to drag
+           if(x >= BOARD_LEFT && x < BOARD_RGHT) clearFlag = 1; // and defer click-click move of empty-square to up-click
+           return;
+       }
        /* Finish clickclick move */
        if (appData.animate || appData.highlightLastMove) {
            SetHighlights(fromX, fromY, toX, toY);