sacred_k/docs/item-stacks.md

Item stacks (potions, combat-art runes)

Requests (2026-10-17)

1. The potion selector on the bottom bar always shows how many potions of each kind the hero carries (only when there are any).
2. Potions of the same type stack in one inventory cell, up to 20 per stack. Every potion entering the inventory tries to stack. Drag, sell and drop move a whole stack. The inventory's sort button stacks first, then sorts. A stack dropped on the ground splits into single potions (agreed for now).

Measured (diagnostic log, 2026-10-17)

Action	Calls
Drink (potion key)	cEngine::UseActionSlot 0x613040 → cCreature::UseItem 0x54a8f0 → RemoveItem (from 0x54aa20) → DestroyObject (from 0x54aa30); then UseActionSlot calls RemoveItem again (0x6130d8, not found)
Drag in the inventory	RemoveAt from 0x6c06fb (cell → cursor), PlaceItem from 0x6c0583 (cursor → cell)
Buy	trader grid (inventory 22) RemoveItem 0x6d96f5 → hero grid PlaceItem 0x6d98e8
Pick up from the ground	PlaceItem from 0x558db6
Trader restock	RemoveItem 0x6d9973 + DestroyObject 0x6d99cc, new items PlaceItem 0x6d9bdf
Sort	cInventoryEntry::Sort 0x5db670: all items removed (0x5db8a5) and placed again (0x5dbb4c, notify 0)

Not seen yet: a sale, a right-click drink.

Game side

• Potion kinds: ItemPotionKind 0x43f630 (ecx = item type table *0xaa9564) maps an item type to kind 1..5 (the bottom bar's potion slots); GetPotionRef 0x5da880 picks the potion a slot drinks.
• Bottom bar: cUI_Taskbar2::RenderPotionSlots 0x6e39e0 draws the 5 slot controls (embedded at +0x258, stride 0xbc).
• Inventory grid (cInventoryEntry, docs/skill-slots.md): cells of 0xc bytes at +0x18; an item's id only in its first cell, covered cells flagged. CellRect 0x5dd530 gives a cell's screen rect (32x32 from the origin +0x1164 / +0x1166, which the window sets before DrawItems 0x5dc3f0).
• Drinking: cPotion3D::vf18 0x5ca9d0 applies the effect and sets object flag +0x14 bit 0x8000000 (used up); UseItem then removes and destroys.
• Sort button: cUI_Inventory3::HandleEvent 0x6c5f40, button control at +0x158, mode from bit 4 of +0x168.
• Hero files map saved item ids to new objects with ReplaceItemId 0x5d80e0.

Mods

• src/mods/potioncounts.cpp: counts per kind (stacks added up), drawn bottom-right on each potion slot after RenderPotionSlots.
• src/mods/itemstack.cpp: stack counts by item id (with the item type), saved as "count" on the grid cell in the JSON inventories (inventory_save.cpp); entry pours into stacks with room on the next tick; Sort stacks the hero's potions first; a drink from a stack of more than one takes one off the count and keeps the object; the count is drawn on the cell after DrawItems.

Open

• Selling a stack: the price is for one potion so far (sale path not measured).
• Dropping a stack on the ground: it should split into single potions; for now the count stays with the object while the game runs, but a save keeps only the object (one potion).

Chest and other inventories (2026-10-17)

Asked: potions stack in every kind of inventory; traders only sell single potions. Measured: the chest is inventory 0x11 (cUI_Chest draws window +0x158), saved with the hero as chunk 0xc6 and in save games, both through the JSON path already (stack sizes survived a reload). Stacking now applies to all inventories below 0x12 (players and the chest); trader stock (0x12 and up) never stacks. Selling a stack to a trader still has to be handled (pay count x price, the trader keeps singles).

Runes (request 2026-10-17: "also allow stacking for combat arts")

• Measured (sort button log of a Rucksack with runes): runes are item class 0x1c (type table +0x2e), 1x1. Two runes of type 0x1517 serialize the same past the object part (id, flags, world position differ), so the type alone identifies a rune.
• The game's own ItemIsConsumable (0x43f5f0, class 9 or 0x1c) now decides what stacks (was: ItemPotionKind). The module was renamed src/mods/itemstack.cpp.
• Reading a rune goes through cCreature::UseItem like a potion (class 0x1c is one of the three classes it uses), so a stack loses one per read.

Rune master (request 2026-10-17: one rune per drop)

(See docs/rune-master.md for the window.) cUI_MasterLotto::HandleEvent (0x6d54e0, read): a left press over one of its four slots (controls at +0x154 + i * 0x114) puts the slot's old rune on the cursor and, if the cursor carries a rune (descriptor at cursor +0x68: {u16 kind 1, u16 class 0x1c, u32 id, ...}), copies the descriptor into the slot (+0x24c + i * 0x114) and clears the cursor. src/mods/runetrade.cpp (owns the event hook; hud.cpp centres it through hud::HandleCentred): for a stack, a single copy (game::CloneItem, serializer round trip) goes into the slot, the stack keeps count - 1 and stays on the cursor; if the slot held a rune (it comes onto the cursor), the rest goes to the backpack instead, and without room the click does nothing.