Item Overrides

The randomizer primitive: replace the item a given chest yields. JS registers (room, chestSlot) → newItem mappings; the game core consults the table when a chest opens. The slot is the chest's ordinal within its room (the Nth chest-table entry for that room), so two chests in one room with identical vanilla contents can carry two different overrides.

Source: core/game-hooks/item_overrides.c · Bridge: lib/game/randomizer.ts

Function	Signature	Effect
WasmSetChestSlotOverride	void(int room_id, int slot, int new_item)	Add or update an override. Matches on (room_id, slot); updates new_item if the pair already exists. Table holds up to 256 entries.
WasmClearItemOverrides	void(void)	Empty the override table.

How it's applied (C → C, no JS event)

When a chest opens, the vendored game code calls the callback GameHook_OverrideChestItem(room_id, slot, original_item). It scans the override table and returns the replacement item id, or the original if none matches. A refused open (the chest stayed locked) passes through untouched. This is a pure C→C hook; see Callbacks for the full callback surface.

flowchart TD
    JS["JS: WasmSetChestSlotOverride(room, slot, new)"] --> T["g_overrides[] table"]
    CHEST["chest opens in core"] --> HOOK["GameHook_OverrideChestItem(room, slot, orig)"]
    HOOK -->|"looks up"| T
    HOOK --> RET["returns new (or orig)"]