Let -sweepPromotions also work for click-click moves

A click-click promotion no longer causes auto-queening, but the down-click
on the to-square causes a Queen to stick to the mouse pointer, and then
allows the user to change it through dragging backwards before releasing it
with an up-click.
  In WinBoard this required a slight change in DragPieceBegin, because
the dragged piece there only was made visible when the mouse pointer
actually started moving (and dragInfo.pos was set), presumably under the
assumption that before mouse move the piece was already on the clicked
square. Which in the case of a to-square was of course not true. (Because
a piece jumps to the mouse pointer when the click is not centered on a
square, this gives less jittery static clicks.) So DragPieceBegin has
been given an extra argument now, to indicate whether it should attach
the piece to the mouse pointer immediately.
  To make the click-click sweepPromotions work in Shogi (for which the
drag-drop sweepPromotions could never work, because it is not clear the
piece has a posibility to promote when you pick it up), translation of
the sweep-selected piece to a Shogi promoChar had to e added.

backend.c

@@ -6080,7 +6080,7 @@ DefaultPromoChoice(int white)
 static int autoQueen; // [HGM] oneclick
 
 int
-HasPromotionChoice(int fromX, int fromY, int toX, int toY, char *promoChoice)
+HasPromotionChoice(int fromX, int fromY, int toX, int toY, char *promoChoice, int sweepSelect)
 {
     /* [HGM] rewritten IsPromotion to only flag promotions that offer a choice */
     /* [HGM] add Shogi promotions */
@@ -6162,9 +6162,9 @@ HasPromotionChoice(int fromX, int fromY, int toX, int toY, char *promoChoice)
     }
     // give caller the default choice even if we will not make it
     *promoChoice = ToLower(PieceToChar(defaultPromoChoice));
-    if(gameInfo.variant == VariantShogi) *promoChoice = '+';
-    if(appData.sweepSelect && gameInfo.variant != VariantGreat
-			   && gameInfo.variant != VariantShogi
+    if(gameInfo.variant == VariantShogi) *promoChoice = (defaultPromoChoice == piece ? '=' : '+');
+    if(        sweepSelect && gameInfo.variant != VariantGreat
+			   && gameInfo.variant != VariantGrand
 			   && gameInfo.variant != VariantSuper) return FALSE;
     if(autoQueen) return FALSE; // predetermined
 
@@ -6819,7 +6819,7 @@ void LeftClick(ClickType clickType, int xPix, int yPix)
 	defaultPromoChoice = promoSweep;
 	promoSweep = EmptySquare;   // terminate sweep
 	promoDefaultAltered = TRUE;
-	if(!selectFlag) x = fromX, y = fromY; // and fake up-click on same square if we were still selecting
+	if(!selectFlag && (x != toX || y != toY)) x = fromX, y = fromY; // and fake up-click on same square if we were still selecting
     }
 
     if(promotionChoice) { // we are waiting for a click to indicate promotion piece
@@ -6872,15 +6872,15 @@ void LeftClick(ClickType clickType, int xPix, int yPix)
 	}
 	return;
       }
-      fromX = x; fromY = y;
+      fromX = x; fromY = y; toX = toY = -1;
       if(!appData.oneClick || !OnlyMove(&x, &y, FALSE) ||
 	 // even if only move, we treat as normal when this would trigger a promotion popup, to allow sweep selection
 	 appData.sweepSelect && CanPromote(boards[currentMove][fromY][fromX], fromY) && originalY != y) {
 	    /* First square */
 	    if (OKToStartUserMove(fromX, fromY)) {
 		second = 0;
 		MarkTargetSquares(0);
-		DragPieceBegin(xPix, yPix); dragging = 1;
+		DragPieceBegin(xPix, yPix, FALSE); dragging = 1;
 		if(appData.sweepSelect && CanPromote(piece = boards[currentMove][fromY][fromX], fromY)) {
 		    promoSweep = defaultPromoChoice;
 		    selectFlag = 0; lastX = xPix; lastY = yPix;
@@ -6935,7 +6935,7 @@ void LeftClick(ClickType clickType, int xPix, int yPix)
 		fromX = x;
 		fromY = y; dragging = 1;
 		MarkTargetSquares(0);
-		DragPieceBegin(xPix, yPix);
+		DragPieceBegin(xPix, yPix, FALSE);
 		if(appData.sweepSelect && CanPromote(piece = boards[currentMove][y][x], y)) {
 		    promoSweep = defaultPromoChoice;
 		    selectFlag = 0; lastX = xPix; lastY = yPix;
@@ -6990,10 +6990,21 @@ void LeftClick(ClickType clickType, int xPix, int yPix)
     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
+	    fromX = x; fromY = y; DragPieceBegin(xPix, yPix, FALSE); 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;
 	}
+	if(appData.sweepSelect && HasPromotionChoice(fromX, fromY, toX, toY, &promoChoice, FALSE)) {
+	    ChessSquare piece = boards[currentMove][fromY][fromX];
+	    DragPieceBegin(xPix, yPix, TRUE); dragging = 1;
+	    promoSweep = defaultPromoChoice;
+	    if(PieceToChar(PROMOTED piece) == '+') promoSweep = PROMOTED piece;
+	    selectFlag = 0; lastX = xPix; lastY = yPix;
+	    Sweep(0); // Pawn that is going to promote: preview promotion piece
+	    DisplayMessage("", _("Pull pawn backwards to under-promote"));
+	    DrawPosition(FALSE, boards[currentMove]);
+	    return;
+	}
 	/* Finish clickclick move */
 	if (appData.animate || appData.highlightLastMove) {
 	    SetHighlights(fromX, fromY, toX, toY);
@@ -7044,7 +7055,7 @@ void LeftClick(ClickType clickType, int xPix, int yPix)
 
     if(gatingPiece != EmptySquare) promoChoice = ToLower(PieceToChar(gatingPiece));
 
-    if (HasPromotionChoice(fromX, fromY, toX, toY, &promoChoice)) {
+    if (HasPromotionChoice(fromX, fromY, toX, toY, &promoChoice, appData.sweepSelect)) {
 	SetHighlights(fromX, fromY, toX, toY);
 	if(gameInfo.variant == VariantSuper || gameInfo.variant == VariantGreat || gameInfo.variant == VariantGrand) {
 	    // [HGM] super: promotion to captured piece selected from holdings

backend.h

@@ -126,7 +126,7 @@ void SetBlackToPlayEvent P((void));
 void UploadGameEvent P((void));
 void InitBackEnd1 P((void));
 void InitBackEnd2 P((void));
-int HasPromotionChoice P((int fromX, int fromY, int toX, int toY, char *choice));
+int HasPromotionChoice P((int fromX, int fromY, int toX, int toY, char *choice, int sweep));
 int InPalace P((int row, int column));
 int PieceForSquare P((int x, int y));
 int OKToStartUserMove P((int x, int y));

frontend.h

@@ -135,7 +135,7 @@ void CancelDelayedEvent P((void));
 extern int fromX, fromY, toX, toY;
 typedef enum { Press, Release } ClickType;
 void PromotionPopUp P((void));
-void DragPieceBegin P((int x, int y));
+void DragPieceBegin P((int x, int y, Boolean instantly));
 void DragPieceEnd P((int x, int y));
 void LeftClick P((ClickType c, int x, int y));
 int  RightClick P((ClickType c, int x, int y, int *col, int *row));

winboard/winboard.c

@@ -4067,10 +4067,11 @@ SetupDropMenu(HMENU hmenu)
   }
 }
 
-void DragPieceBegin(int x, int y)
+void DragPieceBegin(int x, int y, Boolean instantly)
 {
       dragInfo.lastpos.x = boardRect.left + x;
       dragInfo.lastpos.y = boardRect.top + y;
+      if(instantly) dragInfo.pos = dragInfo.lastpos;
       dragInfo.from.x = fromX;
       dragInfo.from.y = fromY;
       dragInfo.piece = boards[currentMove][fromY][fromX];

xboard.c

@@ -8644,8 +8644,8 @@ AnimateMove(board, fromX, fromY, toX, toY)
 }
 
 void
-DragPieceBegin(x, y)
-     int x; int y;
+DragPieceBegin(x, y, instantly)
+     int x; int y; Boolean instantly;
 {
     int	 boardX, boardY, color;
     XPoint corner;