Add function to get item id at grid coords

Also introduced a few helper types and values to hopefully help document behaviour

correct spelling in comment

Co-authored-by: qndel <stefan551@o2.pl>

Source/controls/plrctrls.cpp

@@ -688,13 +688,13 @@ int FindFirstSlotOnItem(int8_t itemInvId)
 	return -1;
 }
 
-Point FindFirstStashSlotOnItem(uint16_t itemInvId)
+Point FindFirstStashSlotOnItem(StashStruct::StashCell itemInvId)
 {
-	if (itemInvId == 0)
+	if (itemInvId == StashStruct::EmptyCell)
 		return InvalidStashPoint;
 
 	for (auto point : PointsInRectangleRange({ { 0, 0 }, { 10, 10 } })) {
-		if (Stash.stashGrids[Stash.GetPage()][point.x][point.y] == itemInvId)
+		if (Stash.GetItemIdAtPosition(point) == itemInvId)
 			return point;
 	}
 
@@ -1772,17 +1772,17 @@ void PerformPrimaryAction()
 			const Size cursorSizeInCells = MyPlayer->HoldItem.isEmpty() ? Size { 1, 1 } : GetInventorySize(MyPlayer->HoldItem);
 
 			// Find any item occupying a slot that is currently under the cursor
-			uint16_t itemUnderCursor = [](Point stashSlot, Size cursorSizeInCells) -> uint16_t {
+			StashStruct::StashCell itemUnderCursor = [](Point stashSlot, Size cursorSizeInCells) -> StashStruct::StashCell {
 				if (stashSlot != InvalidStashPoint)
-					return 0;
+					return StashStruct::EmptyCell;
 				for (Point slotUnderCursor : PointsInRectangleRange { { stashSlot, cursorSizeInCells } }) {
 					if (slotUnderCursor.x >= 10 || slotUnderCursor.y >= 10)
 						continue;
-					uint16_t itemId = Stash.stashGrids[Stash.GetPage()][slotUnderCursor.x][slotUnderCursor.y];
-					if (itemId != 0)
+					StashStruct::StashCell itemId = Stash.GetItemIdAtPosition(slotUnderCursor);
+					if (itemId != StashStruct::EmptyCell)
 						return itemId;
 				}
-				return 0;
+				return StashStruct::EmptyCell;
 			}(stashSlot, cursorSizeInCells);
 
 			// The cursor will need to be shifted to

Source/qol/stash.cpp

@@ -107,14 +107,14 @@ void CheckStashPaste(Point cursorPosition)
 		return; // Item does not fit
 	}
 
-	// Check that no more then 1 item is replaced by the move
-	uint16_t it = 0;
+	// Check that no more than 1 item is replaced by the move
+	StashStruct::StashCell stashIndex = StashStruct::EmptyCell;
 	for (auto point : PointsInRectangleRange({ firstSlot, itemSize })) {
-		uint16_t iv = Stash.stashGrids[Stash.GetPage()][point.x][point.y];
-		if (iv == 0 || it == iv)
+		StashStruct::StashCell iv = Stash.GetItemIdAtPosition(point);
+		if (iv == StashStruct::EmptyCell || stashIndex == iv)
 			continue;
-		if (it == 0) {
-			it = iv; // Found first item
+		if (stashIndex == StashStruct::EmptyCell) {
+			stashIndex = iv; // Found first item
 			continue;
 		}
 		return; // Found a second item
@@ -125,16 +125,16 @@ void CheckStashPaste(Point cursorPosition)
 	player.HoldItem.position = firstSlot + Displacement { 0, itemSize.height - 1 };
 
 	int cn = CURSOR_HAND;
-	uint16_t stashIndex;
-	if (it == 0) {
+	if (stashIndex == StashStruct::EmptyCell) {
 		Stash.stashList.push_back(player.HoldItem);
-		stashIndex = Stash.stashList.size() - 1;
+		// stashList will have at most 10 000 items, up to 65 535 are supported with uint16_t indexes
+		stashIndex = static_cast<uint16_t>(Stash.stashList.size() - 1);
 	} else {
-		stashIndex = it - 1;
+		// remove item from stash grid
 		cn = SwapItem(Stash.stashList[stashIndex], player.HoldItem);
 		for (auto &row : Stash.GetCurrentGrid()) {
 			for (auto &itemId : row) {
-				if (itemId == it)
+				if (itemId - 1 == stashIndex)
 					itemId = 0;
 			}
 		}
@@ -185,10 +185,8 @@ void CheckStashCut(Point cursorPosition, bool automaticMove)
 	bool automaticallyMoved = false;
 	bool automaticallyEquipped = false;
 
-	uint16_t ii = Stash.stashGrids[Stash.GetPage()][slot.x][slot.y];
-	if (ii != 0) {
-		uint16_t iv = ii - 1;
-
+	StashStruct::StashCell iv = Stash.GetItemIdAtPosition(slot);
+	if (iv != StashStruct::EmptyCell) {
 		holdItem = Stash.stashList[iv];
 		if (automaticMove) {
 			if (CanBePlacedOnBelt(holdItem)) {
@@ -343,18 +341,17 @@ void DrawStash(const Surface &out)
 	constexpr Displacement offset { 0, INV_SLOT_SIZE_PX - 1 };
 
 	for (auto slot : PointsInRectangleRange({ { 0, 0 }, { 10, 10 } })) {
-		if (Stash.stashGrids[Stash.GetPage()][slot.x][slot.y] != 0) {
+		if (Stash.IsItemAtPosition(slot)) {
 			InvDrawSlotBack(out, GetStashSlotCoord(slot) + offset, InventorySlotSizeInPixels);
 		}
 	}
 
 	for (auto slot : PointsInRectangleRange({ { 0, 0 }, { 10, 10 } })) {
-		uint16_t itemId = Stash.stashGrids[Stash.GetPage()][slot.x][slot.y];
-		if (itemId == 0) {
+		StashStruct::StashCell itemId = Stash.GetItemIdAtPosition(slot);
+		if (itemId == StashStruct::EmptyCell) {
 			continue; // No item in the given slot
 		}
 
-		itemId -= 1;
 		Item &item = Stash.stashList[itemId];
 		if (item.position != slot) {
 			continue; // Not the first slot of the item
@@ -414,12 +411,11 @@ uint16_t CheckStashHLight(Point mousePosition)
 
 	ClearPanel();
 
-	uint16_t itemId = Stash.stashGrids[Stash.GetPage()][slot.x][slot.y];
-	if (itemId == 0) {
+	StashStruct::StashCell itemId = Stash.GetItemIdAtPosition(slot);
+	if (itemId == StashStruct::EmptyCell) {
 		return -1;
 	}
 
-	itemId -= 1;
 	Item &item = Stash.stashList[itemId];
 	if (item.isEmpty()) {
 		return -1;
@@ -499,11 +495,11 @@ bool UseStashItem(uint16_t c)
 	return true;
 }
 
-void StashStruct::RemoveStashItem(uint16_t iv)
+void StashStruct::RemoveStashItem(StashStruct::StashCell iv)
 {
 	// Iterate through stashGrid and remove every reference to item
 	for (auto &row : Stash.GetCurrentGrid()) {
-		for (uint16_t &itemId : row) {
+		for (StashStruct::StashCell &itemId : row) {
 			if (itemId - 1 == iv) {
 				itemId = 0;
 			}
@@ -515,14 +511,14 @@ void StashStruct::RemoveStashItem(uint16_t iv)
 	}
 
 	// If the item at the end of stash array isn't the one we removed, we need to swap its position in the array with the removed item
-	std::size_t lastItemIndex = stashList.size() - 1;
+	StashStruct::StashCell lastItemIndex = static_cast<StashStruct::StashCell>(stashList.size() - 1);
 	if (lastItemIndex != iv) {
 		stashList[iv] = stashList[lastItemIndex];
 
 		for (auto &pair : Stash.stashGrids) {
 			auto &grid = pair.second;
 			for (auto &row : grid) {
-				for (uint16_t &itemId : row) {
+				for (StashStruct::StashCell &itemId : row) {
 					if (itemId == lastItemIndex + 1) {
 						itemId = iv + 1;
 					}
@@ -689,7 +685,7 @@ bool AutoPlaceItemInStash(Player &player, const Item &item, bool persistItem)
 				continue;
 			if (persistItem) {
 				Stash.stashList.push_back(item);
-				uint16_t stashIndex = Stash.stashList.size() - 1;
+				uint16_t stashIndex = static_cast<uint16_t>(Stash.stashList.size() - 1);
 				Stash.stashList[stashIndex].position = stashPosition + Displacement { 0, itemSize.height - 1 };
 				AddItemToStashGrid(pageIndex, stashPosition, stashIndex, itemSize);
 				Stash.dirty = true;

Source/qol/stash.h

@@ -16,8 +16,11 @@ namespace devilution {
 
 class StashStruct {
 public:
-	void RemoveStashItem(uint16_t iv);
-	using StashGrid = std::array<std::array<uint16_t, 10>, 10>;
+	using StashCell = uint16_t;
+	using StashGrid = std::array<std::array<StashCell, 10>, 10>;
+	static constexpr StashCell EmptyCell = -1;
+
+	void RemoveStashItem(StashCell iv);
 	std::map<unsigned, StashGrid> stashGrids;
 	std::vector<Item> stashList;
 	int gold;
@@ -33,6 +36,22 @@ public:
 		return stashGrids[GetPage()];
 	}
 
+	/**
+	 * @brief Returns the 0-based index of the item at the specified position, or EmptyCell if no item occupies that slot
+	 * @param gridPosition x,y coordinate of the current stash page
+	 * @return a value which can be used to index into stashList or StashStruct::EmptyCell
+	 */
+	StashCell GetItemIdAtPosition(Point gridPosition)
+	{
+		// Because StashCell is an unsigned type we can let this underflow
+		return GetCurrentGrid()[gridPosition.x][gridPosition.y] - 1;
+	}
+
+	bool IsItemAtPosition(Point gridPosition)
+	{
+		return GetItemIdAtPosition(gridPosition) != EmptyCell;
+	}
+
 	void SetPage(unsigned newPage);
 	void NextPage(unsigned offset = 1);
 	void PreviousPage(unsigned offset = 1);