# D.2b toolbar shortcut drag interactivity (Stream B.2) — design

**Date:** 2026-06-20
**Phase:** D.2b retail-UI → D.5 core panels. Stream **B.2** of the 2026-06-18 handoff — make the
toolbar shortcut drag *functional* (reorder / remove) and *retail-faithful*, on top of the B.1
spine (`9d48346..acdefc2`, shipped + visually confirmed this session).
**Branch:** `claude/hopeful-maxwell-214a12`.
**Driver:** user visual-gate feedback 2026-06-20 (6 points) + the retail research below.

**Read alongside:**
- `docs/research/2026-06-16-action-bar-toolbar-deep-dive.md` §5 (HandleDropRelease/RemoveShortcut/wire).
- `docs/research/2026-06-16-ui-item-slot-icon-dragdrop-spine-deep-dive.md` §5 (the cell drag chain).
- `docs/superpowers/specs/2026-06-20-d2b-drag-drop-spine-design.md` (B.1 — what this extends).
- `claude-memory/project_d2b_retail_ui.md`.

---

## 1. Goal & non-goals

**Goal.** A player drags a hotbar shortcut, sees the item icon lift off the slot (slot empties) and
follow the cursor at full opacity with a green-cross drop indicator; dropping on another slot moves
it there (reordering, bumping any occupant back to the source slot); dropping anywhere else removes
it from the bar. All changes are sent to the server (`AddShortcut 0x019C` / `RemoveShortcut 0x019D`)
so they persist. This realizes the user's 6 visual-gate points as retail's single **remove-on-lift /
place-on-drop / no-restore** mechanism.

**In scope:**
1. **Spine extensions** (small, to the B.1 toolkit): a drag-LIFT hook to the source's handler;
   full-opacity ghost snapshotted at drag-begin (survives the source emptying); `FinishDrag`
   delivers a drop only when released on a real element (off-bar = no drop fires).
2. **`ShortcutStore`** — a mutable 18-slot model (port of retail `ShortCutManager::shortCuts_[18]`).
3. **`ToolbarController` as the live drag handler** — `OnDragLift` removes; `HandleDropRelease`
   places + bumps displaced → source; both drive the store, the wire, and a re-`Populate()`.
4. **The wire** — fix `BuildAddShortcut` param names; add `WorldSession.SendAddShortcut` /
   `SendRemoveShortcut`.
5. **Green-cross accept overlay** (`0x060011FA`) on toolbar cells (verified against the dat).

**Out of scope (later streams):**
- **Drag FROM inventory onto the bar** (the `flags & 0xE == 0` "fresh-from-inventory" branch) — needs
  the inventory window as a drag source (Stream C). This spec is reorder-within-bar + remove only
  (the `flags & 4` branch).
- Spell shortcuts (the `SpellId|Layer` payload) — items only (`spellId=layer=0`); the store carries a
  spell field for forward-compat but the toolbar binds item guids.
- Server-pushed shortcut mutations after login (the store is client-authoritative post-`Load`).
- The selected-object mana meter / stack-split UI (issue #141 deferred bits).

---

## 2. Retail grounding (the model — CONFIRMED by research 2026-06-20)

Retail's toolbar drag is **remove-on-lift, place-on-drop, no-restore** (decomp trace, this session):

- **On drag-begin** (`UIElement_ItemList::ItemList_BeginDrag` 0x004e32d0 → broadcasts msg `0x21` →
  `gmToolbarUI::RecvNotice_ItemListBeginDrag` 0x004bd930): `PrepareDragIcon` makes the **full icon**
  the cursor ghost (m_dragIcon), then `gmToolbarUI::RemoveShortcut` (0x004bd450) **removes the
  shortcut**: `ItemList_Flush` → cell → empty state `0x1000001c`, `Event_RemoveShortCut` sends
  `0x019D`, and `m_lastShortcutNumDragged` = the source slot. The slot is now empty; the item is "in
  hand."
- **On mouse-up over a slot** (`UIElementManager::StopDragandDrop` 0x00459810 → success →
  `gmToolbarUI::HandleDropRelease` 0x004be7c0): within-bar reorder branch (`flags & 4`):
  `RemoveShortcutInSlotNum(target)` (evict the occupant, get its objId) → `AddShortcut(draggedObjId,
  target)` (`0x019C`); if an item was displaced and the source slot is free, `AddShortcut(displaced,
  m_lastShortcutNumDragged)` — the bumped item lands in the vacated source slot. (deep-dive §5.)
- **On mouse-up over nothing** (`m_pElementLastDragCursorOver == null` → success=0): no
  `HandleDropRelease`, no re-add — the shortcut stays gone (already removed + `0x019D` sent at lift).
- **No cancel/restore path.** `gmToolbarUI` has no end-drag/restore vtable entry. Lifted-then-not-
  landed = permanently removed (server already told).
- **Drop indicator** is a per-slot OVERLAY sprite on `m_elem_Icon_DragAccept` (`0x1000045A`), NOT a
  cursor change (`UpdateCursorState` is combat/target-only). The toolbar accept sprite is the **green
  cross `0x060011FA`** (verified by exporting the `0x060011F7..FA` family from `client_portal.dat`:
  F7=green move-arrow, F8=red ∅ reject, F9=green **ring** [inventory], FA=green **cross** [toolbar]);
  reject = `0x060011F8`.

**Wire (`ShortCutData`, CONFIRMED 3 refs — deep-dive §131-145):**
- `AddShortCut 0x019C` body after the 12-byte GameAction envelope: `Index(u32), ObjectId(u32),
  SpellId(u16), Layer(u16)` (item → `ObjectId=guid, SpellId=Layer=0`).
- `RemoveShortCut 0x019D` body: `Index(u32)`.
- ACE handles the remove-then-add reorder pattern (`Player_Character.cs:254`).

---

## 3. Architecture — components & boundaries

```
 press+move on OCCUPIED slot ─► UiRoot.BeginDrag
   │  snapshot ghost (full icon) BEFORE the lift clears the source cell
   │  fire DragBegin on the source cell
   ▼
 UiItemSlot.OnEvent(DragBegin) ─► FindList().DragHandler.OnDragLift(list, cell, payload)
   ▼
 ToolbarController.OnDragLift ─► ShortcutStore.Remove(srcSlot); SendRemoveShortcut(srcSlot); Populate()
                                  (source slot now empty; ghost still shows the snapshot)
 drag-over target slot ─► UiItemSlot DragEnter ─► handler.OnDragOver → green-cross accept overlay (FA)
 release ─► UiRoot.FinishDrag:
   ├─ over a slot  ─► that cell.OnEvent(DropReleased) ─► handler.HandleDropRelease(target, payload)
   │                    ShortcutStore place + bump displaced→srcSlot; SendAddShortcut×N; Populate()
   └─ over nothing ─► no DropReleased delivered → lift's removal stands (item gone)
```

**Boundaries:** `UiRoot`/`UiElement`/`UiItemSlot`/`UiItemList` stay item-agnostic — they gain a lift
*hook* and a ghost snapshot, nothing item-specific. `ShortcutStore` is pure logic in `AcDream.Core`
(testable, no GL). The wire lives in `AcDream.Core.Net`. `ToolbarController` (App) orchestrates.
Honors structure Rules 1/2/3/6.

---

## 4. New & changed types (precise)

### 4.1 Spine — `IItemListDragHandler` gains the lift hook (`UI/IItemListDragHandler.cs`)
```csharp
public interface IItemListDragHandler
{
    /// <summary>The drag STARTED from a cell in this list — retail's
    /// RecvNotice_ItemListBeginDrag → RemoveShortcut (decomp 0x004bd930/0x004bd450): the handler
    /// removes the lifted item from its model + wire, so the source slot empties immediately. The
    /// item is "in hand" until HandleDropRelease (place) or the drag ends off-target (stays removed).</summary>
    void OnDragLift(UiItemList sourceList, UiItemSlot sourceCell, ItemDragPayload payload);

    bool OnDragOver(UiItemList targetList, UiItemSlot targetCell, ItemDragPayload payload);
    void HandleDropRelease(UiItemList targetList, UiItemSlot targetCell, ItemDragPayload payload);
}
```

### 4.2 Spine — `UiItemSlot` (`UI/UiItemSlot.cs`)
- `OnEvent` `DragBegin` case changes from `return true` (no-op) to: notify the list's handler so it
  can lift:
  ```csharp
  case UiEventType.DragBegin:
      if (FindList() is { DragHandler: { } h } list && e.Payload is ItemDragPayload p)
          h.OnDragLift(list, this, p);
      return true;
  ```
- `DropReleased` case: drop the `e.Data0 == 1` gate — reaching the cell means a real slot was hit
  (`FinishDrag` only delivers on a hit). The handler is authoritative (place; drop-on-self re-adds):
  ```csharp
  case UiEventType.DropReleased:
      _dragAccept = DragAcceptState.None;
      if (FindList() is { DragHandler: { } dh } dl && e.Payload is ItemDragPayload dp)
          dh.HandleDropRelease(dl, this, dp);
      return true;
  ```
  (`DragEnter`/`DragOver` overlay handling unchanged from B.1.)

### 4.3 Spine — `UiRoot` (`UI/UiRoot.cs`)
- Add `private (uint tex, int w, int h)? _dragGhost;`. In `BeginDrag`, **snapshot the ghost before
  firing `DragBegin`** (the lift will empty the source cell, so a live re-read would vanish):
  ```csharp
  private void BeginDrag(UiElement source)
  {
      var payload = source.GetDragPayload();
      if (payload is null) { _dragCandidate = false; return; }
      DragSource  = source;
      DragPayload = payload;
      _dragGhost  = source.GetDragGhost();      // snapshot NOW — survives the source emptying
      var e = new UiEvent(source.EventId, source, UiEventType.DragBegin, Payload: payload);
      source.OnEvent(in e);                      // → cell → handler.OnDragLift (clears the source slot)
  }
  ```
- `DrawDragGhost` uses the snapshot, not a live read; `GhostAlpha` → **1.0** (full opacity, retail
  m_dragIcon):
  ```csharp
  private const float GhostAlpha = 1.0f;
  private void DrawDragGhost(UiRenderContext ctx)
  {
      if (_dragGhost is not { } g || g.tex == 0) return;
      ctx.DrawSprite(g.tex, MouseX - g.w / 2f, MouseY - g.h / 2f, g.w, g.h,
                     0f, 0f, 1f, 1f, new Vector4(1f, 1f, 1f, GhostAlpha));
  }
  ```
- `FinishDrag` delivers a drop ONLY to a real hit element; off-bar (null hit) fires nothing; clear
  the ghost:
  ```csharp
  private void FinishDrag(int x, int y)
  {
      var (t, lx, ly) = HitTestTopDown(x, y);
      if (t is not null)
      {
          var e = new UiEvent(DragSource!.EventId, t, UiEventType.DropReleased,
                              Data1: (int)lx, Data2: (int)ly, Payload: DragPayload);
          t.OnEvent(in e);   // the hit cell's handler places; a non-item target ignores it → item stays removed
      }
      // else: dropped off any element — no drop fires; the lift's removal stands (retail).
      DragSource = null; DragPayload = null; _dragGhost = null; _lastDragHoverTarget = null;
  }
  ```
  (`GetDragGhost()` on `UiElement`/`UiItemSlot` stays as-is — `BeginDrag` calls it once.)

### 4.4 NEW — `ShortcutStore` (`src/AcDream.Core/Items/ShortcutStore.cs`)
Port of retail `ShortCutManager::shortCuts_[18]` (`acclient.h:36492`). Pure logic.
```csharp
public sealed class ShortcutStore
{
    public const int SlotCount = 18;
    private readonly uint[] _objIds = new uint[SlotCount];   // 0 = empty

    /// <summary>Replace all slots from the login PlayerDescription shortcut list.</summary>
    public void Load(IReadOnlyList<PlayerDescriptionParser.ShortcutEntry> entries)
    {
        System.Array.Clear(_objIds);
        foreach (var e in entries)
            if (e.Index < SlotCount && e.ObjectGuid != 0) _objIds[e.Index] = e.ObjectGuid;
    }

    public uint Get(int slot) => (uint)slot < SlotCount ? _objIds[slot] : 0u;
    public bool IsEmpty(int slot) => Get(slot) == 0u;
    public void Set(int slot, uint objId) { if ((uint)slot < SlotCount) _objIds[slot] = objId; }
    public void Remove(int slot) { if ((uint)slot < SlotCount) _objIds[slot] = 0u; }
}
```

### 4.5 Wire — `InventoryActions.BuildAddShortcut` rename (`Core.Net/Messages/InventoryActions.cs`)
Byte layout is already correct; FIX the misleading param names (handoff §B.2; deep-dive §131-145):
```csharp
/// <summary>Pin an item/spell to a quickbar slot. ShortCutData = Index(u32),ObjectId(u32),
/// SpellId(u16),Layer(u16). For an item: objectGuid + spellId=layer=0.</summary>
public static byte[] BuildAddShortcut(uint seq, uint index, uint objectGuid, ushort spellId, ushort layer)
{
    byte[] body = new byte[24];
    BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
    BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  seq);
    BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  AddShortcutOpcode);   // 0x019C
    BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), index);
    BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(16), objectGuid);
    BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(20), spellId);
    BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(22), layer);
    return body;
}
```
(`BuildRemoveShortcut(seq, slotIndex)` is correct — unchanged.) Any existing caller of the old
4-arg `BuildAddShortcut` must be updated; grep first (likely none wired today).

### 4.6 Wire — `WorldSession` sends (`Core.Net/WorldSession.cs`, mirror `SendChangeCombatMode` :1134)
```csharp
public void SendAddShortcut(uint index, uint objectGuid, ushort spellId = 0, ushort layer = 0)
{
    uint seq = NextGameActionSequence();
    SendGameAction(InventoryActions.BuildAddShortcut(seq, index, objectGuid, spellId, layer));
}
public void SendRemoveShortcut(uint index)
{
    uint seq = NextGameActionSequence();
    SendGameAction(InventoryActions.BuildRemoveShortcut(seq, index));
}
```

### 4.7 `ToolbarController` — the live handler (`UI/Layout/ToolbarController.cs`)
- Holds a `ShortcutStore _store`. `Populate()` reads `_store` (18 slots → `repo.Get(objId)` → icon)
  INSTEAD of the read-only `_shortcuts()` provider. **Lazy-load-once:** the PlayerDescription shortcut
  list arrives AFTER Bind (at login), so load the store the first time `_shortcuts()` is non-empty,
  then treat it as authoritative:
  ```csharp
  // top of Populate(), before rendering:
  if (!_storeLoaded && _shortcuts().Count > 0) { _store.Load(_shortcuts()); _storeLoaded = true; }
  ```
  Bind's initial `Populate` (pre-login) sees an empty list and skips the load; the existing
  `repo.ObjectAdded → Populate` path (shortcut items arriving via `CreateObject`, by which time the PD
  shortcut list is set) triggers the one-time load. After load, drag ops mutate `_store` directly and
  it is never reloaded within the session (a relog = a fresh process → `_storeLoaded` resets). No
  GameWindow change is needed for loading.
- `IsShortcutGuid(guid)` (the repo-event gate) checks `_store` (any slot holds `guid`) rather than
  `_shortcuts()`, so an item dragged ONTO the bar (a new guid) still gets its later updates rendered.
- Each toolbar cell: `DragAcceptSprite = 0x060011FAu` (green cross). (`DragRejectSprite` stays
  `0x060011F8`.)
- Inject two `Action`s for the wire (so the controller stays testable without a live session):
  `Action<uint,uint> sendAdd` = `(index, objId) => session.SendAddShortcut(index, objId)`,
  `Action<uint> sendRemove` = `index => session.SendRemoveShortcut(index)`. Null in tests.
- `OnDragLift(sourceList, sourceCell, payload)` — retail `RemoveShortcut`:
  ```csharp
  _store.Remove(payload.SourceSlot);
  _sendRemove?.Invoke((uint)payload.SourceSlot);
  Populate();
  ```
- `HandleDropRelease(targetList, targetCell, payload)` — retail reorder branch (deep-dive §5):
  ```csharp
  int target = targetCell.SlotIndex;
  uint evicted = _store.Get(target);                       // RemoveShortcutInSlotNum
  if (evicted != 0) { _store.Remove(target); _sendRemove?.Invoke((uint)target); }
  _store.Set(target, payload.ObjId); _sendAdd?.Invoke((uint)target, payload.ObjId);   // AddShortcut
  if (evicted != 0 && evicted != payload.ObjId && _store.IsEmpty(payload.SourceSlot))
  {                                                        // bump displaced → vacated source slot
      _store.Set(payload.SourceSlot, evicted);
      _sendAdd?.Invoke((uint)payload.SourceSlot, evicted);
  }
  Populate();
  ```
- `OnDragOver` unchanged from B.1 (accept any real item → green-cross overlay).

---

## 5. Data flow — frame by frame (reorder slot 3 → occupied slot 5)

1. Press+move on slot 3 (objId A). `BeginDrag`: snapshot ghost = A's icon; fire `DragBegin`.
2. Cell 3 → `OnDragLift`: `_store.Remove(3)` + `SendRemoveShortcut(3)` (0x019D) + `Populate()` →
   slot 3 shows empty. Ghost (A's full icon) follows the cursor.
3. Drag over slot 5 (objId B) → green-cross accept overlay on slot 5.
4. Release on slot 5 → `FinishDrag` delivers `DropReleased` to cell 5 → `HandleDropRelease`:
   `evicted=B`; `Remove(5)`+`SendRemoveShortcut(5)`; `Set(5,A)`+`SendAddShortcut(5,A)`; source slot 3
   is empty → `Set(3,B)`+`SendAddShortcut(3,B)`; `Populate()` → slot 5 = A, slot 3 = B (swapped).
5. (Off-bar variant) release over the 3D world → no `DropReleased` → A stays removed → slot 3 empty,
   A gone from the bar (server already told at step 2).

---

## 6. Edge cases

- **Drop on self (slot 3 → slot 3):** at lift slot 3 emptied; at drop `evicted=0`, `Set(3,A)` +
  `SendAddShortcut(3,A)` → A back at 3. Net no-op (2 wire msgs — retail does the same).
- **Drop on a non-item element** (chrome / another window): `FinishDrag` delivers `DropReleased` to
  it; its `OnEvent` doesn't handle it → no place → A stays removed (off-bar). Correct.
- **Ghost lifetime:** snapshotted at `BeginDrag`, cleared in `FinishDrag` — independent of the source
  cell emptying. A cancelled drag (mouse-up off-bar) still clears `_dragGhost`.
- **Empty-slot lift:** an empty slot is not a drag source (`IsDragSource => ItemId != 0` from B.1) →
  no drag arms → no lift. (And empty slots still move the window — IA-12, from B.1.)
- **Spell shortcuts in the loaded list** (`ObjectGuid == 0`, a spell): `ShortcutStore.Load` skips
  them (item-only this stream); they neither render nor drag. Forward-compat: the store could hold
  spell entries later.

---

## 7. Divergence register (update in the implementation commits)

- **AP-47 (amend):** the ghost is now **full opacity** (retail m_dragIcon) — retire the
  `GhostAlpha=0.6` reduced-alpha approximation. The row's REMAINING approximation: the ghost reuses
  the full composited `m_pIcon` (which includes the type-default underlay) rather than retail's
  dedicated underlay-less `m_pDragIcon`. Reword AP-47 to drop the alpha claim, keep the underlay note.
- **TS-33 (retire):** the toolbar `HandleDropRelease` logging stub is replaced by the real
  store-mutation + `AddShortcut`/`RemoveShortcut` wire. Delete the row.
- **No new row** for remove-on-lift / off-bar-remove — it is the faithful retail mechanism (it
  *reduces* divergence). The store being client-authoritative post-login matches retail's
  `ShortCutManager` (client owns the array; server is notified via the wire).

---

## 8. Testing (conformance)

Core tests (`tests/AcDream.Core.Tests/`):
1. `ShortcutStore`: `Load` maps Index→ObjId (skips ObjectGuid==0 + out-of-range); `Set`/`Remove`/
   `Get`/`IsEmpty`; bounds-safe.
2. `BuildAddShortcut`: 24-byte body, envelope+seq+`0x019C`+index+objectGuid+spellId(u16)+layer(u16) at
   the right offsets (golden bytes). `BuildRemoveShortcut`: 16 bytes, index at +12.

App tests (`tests/AcDream.App.Tests/`):
3. Spine: `BeginDrag` snapshots the ghost so it survives the source cell being cleared mid-drag (clear
   the source cell after begin; assert the drawn ghost source is still the snapshot — assert via a
   testable `UiRoot` accessor for `_dragGhost`).
4. Spine: `FinishDrag` over null delivers NO `DropReleased` (a spy cell/handler isn't called); over a
   real cell, delivers it (drop the Data0 gate — drop-on-self now dispatches).
5. `ToolbarController.OnDragLift`: removes the source slot from the store, invokes `sendRemove(src)`,
   and the source cell empties after `Populate`.
6. `ToolbarController.HandleDropRelease` reorder onto an OCCUPIED target: store ends with dragged@target
   + displaced@source; `sendRemove`+`sendAdd` called with the retail sequence/args. Onto an EMPTY
   target: dragged@target, source stays empty, displaced-branch not taken. Drop-on-self: re-adds to
   source.
7. Update the B.1 tests changed by §4.2/§4.3: `DropReleased_notAccepted_skipsDispatch` →
   `DropReleased_alwaysDispatchesToHandler` (the cell dispatches whenever it receives a DropReleased);
   the full-chain drag tests still pass (a completed reorder fires `HandleDropRelease`, not `Clicked`).

---

## 9. Acceptance criteria

- [ ] `dotnet build` + `dotnet test` green (Core + App).
- [ ] AP-47 reworded (no alpha); TS-33 deleted; wire builder renamed; no stray old-signature callers.
- [ ] `UiRoot`/`UiElement`/`UiItemSlot` remain item-agnostic (the lift hook is generic; only
      `ToolbarController` knows shortcuts).
- [ ] **Visual (user), `ACDREAM_RETAIL_UI=1`, in-world:** lift a hotbar item → **slot empties
      immediately**, **full-opacity** icon follows the cursor with a **green cross** over hovered
      slots; drop on another slot → it **moves there** (occupant bumps to the source slot); drop
      off-bar → it's **removed**; a single click still **uses** the item. Changes **persist after
      relog** (the wire reached ACE).
- [ ] Memory crib + roadmap/ISSUES updated; #141's note refreshed if relevant.

---

## 10. Subagent task slices

1. **Core: `ShortcutStore` + wire** — `ShortcutStore.cs` + `BuildAddShortcut` rename +
   `WorldSession.SendAddShortcut`/`SendRemoveShortcut` + Core tests (§8.1-2).
2. **Spine extensions** — `IItemListDragHandler.OnDragLift`; `UiItemSlot` DragBegin→lift + DropReleased
   ungate; `UiRoot` ghost snapshot + full opacity + `FinishDrag` deliver-on-hit-only; update the B.1
   tests (§8.3-4, §8.7).
3. **ToolbarController handler** — `_store` + `Load` + `Populate`-from-store; green-cross sprite;
   `OnDragLift`/`HandleDropRelease`; wire `Action`s; GameWindow injects the session sends; controller
   tests (§8.5-6). Update AP-47, delete TS-33.

(1 and 2 are independent; 3 depends on both.)