disallow dropping a card onto another

cockatrice/src/carddragitem.cpp

@@ -5,12 +5,21 @@
 #include <QGraphicsScene>
 #include <QGraphicsSceneMouseEvent>
 #include <QCursor>
+#include <QPainter>
 
 CardDragItem::CardDragItem(CardItem *_item, int _id, const QPointF &_hotSpot, bool _faceDown, AbstractCardDragItem *parentDrag)
-	: AbstractCardDragItem(_item, _hotSpot, parentDrag), id(_id), faceDown(_faceDown), currentZone(0)
+	: AbstractCardDragItem(_item, _hotSpot, parentDrag), id(_id), faceDown(_faceDown), occupied(false), currentZone(0)
 {
 }
 
+void CardDragItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
+{
+	AbstractCardDragItem::paint(painter, option, widget);
+	
+	if (occupied)
+		painter->fillRect(boundingRect(), QColor(200, 0, 0, 100));
+}
+
 void CardDragItem::updatePosition(const QPointF &cursorScenePos)
 {
 	QList<QGraphicsItem *> colliding = scene()->items(cursorScenePos);
@@ -36,12 +45,23 @@ void CardDragItem::updatePosition(const QPointF &cursorScenePos)
 	QPointF zonePos = currentZone->scenePos();
 	QPointF cursorPosInZone = cursorScenePos - zonePos;
 	QPointF cardTopLeft = cursorPosInZone - hotSpot;
-	QPointF newPos = zonePos + cursorZone->closestGridPoint(cardTopLeft);
+	QPointF closestGridPoint = cursorZone->closestGridPoint(cardTopLeft);
+	QPointF newPos = zonePos + closestGridPoint;
 	
 	if (newPos != pos()) {
 		for (int i = 0; i < childDrags.size(); i++)
 			childDrags[i]->setPos(newPos + childDrags[i]->getHotSpot());
 		setPos(newPos);
+		
+		bool newOccupied = false;
+		TableZone *table = qobject_cast<TableZone *>(cursorZone);
+		if (table)
+			if (table->getCardFromCoords(closestGridPoint))
+				newOccupied = true;
+		if (newOccupied != occupied) {
+			occupied = newOccupied;
+			update();
+		}
 	}
 }
 
@@ -54,10 +74,11 @@ void CardDragItem::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
 
 	CardZone *startZone = static_cast<CardItem *>(item)->getZone();
 	if (currentZone && !(static_cast<CardItem *>(item)->getAttachedTo() && (startZone == currentZone))) {
-		currentZone->handleDropEvent(id, startZone, (sp - currentZone->scenePos()).toPoint(), faceDown);
+		if (!occupied)
+			currentZone->handleDropEvent(id, startZone, (sp - currentZone->scenePos()).toPoint(), faceDown);
 		for (int i = 0; i < childDrags.size(); i++) {
 			CardDragItem *c = static_cast<CardDragItem *>(childDrags[i]);
-			if (!(static_cast<CardItem *>(c->item)->getAttachedTo() && (startZone == currentZone)))
+			if (!(static_cast<CardItem *>(c->item)->getAttachedTo() && (startZone == currentZone)) && !c->occupied)
 				currentZone->handleDropEvent(c->id, startZone, (sp - currentZone->scenePos() + c->getHotSpot()).toPoint(), faceDown);
 			sc->removeItem(c);
 		}

cockatrice/src/carddragitem.h

@@ -9,9 +9,11 @@ class CardDragItem : public AbstractCardDragItem {
 private:
 	int id;
 	bool faceDown;
+	bool occupied;
 	CardZone *currentZone;
 public:
 	CardDragItem(CardItem *_item, int _id, const QPointF &_hotSpot, bool _faceDown, AbstractCardDragItem *parentDrag = 0);
+	void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
 	void updatePosition(const QPointF &cursorScenePos);
 protected:
 	void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);

cockatrice/src/tablezone.cpp

@@ -202,6 +202,13 @@ CardItem *TableZone::getCardFromGrid(const QPoint &gridPoint) const
 	return 0;
 }
 
+CardItem *TableZone::getCardFromCoords(const QPointF &point) const
+{
+	QPoint gridPoint = mapToGrid(point);
+	return getCardFromGrid(gridPoint);
+}
+
+	
 QPointF TableZone::mapFromGrid(const QPoint &gridPoint) const
 {
 	if ((gridPoint.y() == 3) && (settingsCache->getEconomicGrid()))

cockatrice/src/tablezone.h

@@ -30,6 +30,7 @@ public:
 	void handleDropEvent(int cardId, CardZone *startZone, const QPoint &dropPoint, bool faceDown = false);
 	void handleDropEventByGrid(int cardId, CardZone *startZone, const QPoint &gridPoint, bool faceDown = false, bool tapped = false);
 	CardItem *getCardFromGrid(const QPoint &gridPoint) const;
+	CardItem *getCardFromCoords(const QPointF &point) const;
 	QPointF mapFromGrid(const QPoint &gridPoint) const;
 	QPoint mapToGrid(const QPointF &mapPoint) const;
 	QPointF closestGridPoint(const QPointF &point);

common/server_protocolhandler.cpp

@@ -512,6 +512,12 @@ ResponseCode Server_ProtocolHandler::moveCard(Server_Game *game, Server_Player *
 	if ((!startzone) || (!targetzone))
 		return RespNameNotFound;
 
+	// Collision detection
+	if (targetzone->hasCoords())
+		for (int i = 0; i < targetzone->cards.size(); ++i)
+			if ((targetzone->cards[i]->getX() == x) && (targetzone->cards[i]->getY() == y))
+				return RespContextError;
+		
 	int position = -1;
 	Server_Card *card = startzone->getCard(_cardId, true, &position);
 	if (!card)