609ed8bfc2
Port ItemList_BeginDrag's select-before-waiting order so a direct press-drag shows the selection indicator on its first frame across inventory, paperdoll, and toolbar item lists. Co-Authored-By: Codex <codex@openai.com>
121 lines
5 KiB
Markdown
121 lines
5 KiB
Markdown
# Retail item drag visuals — pseudocode
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Date: 2026-07-13
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Scope: the cursor graphic and source-cell visual while dragging an item from an
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item list. This is a focused continuation of
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`2026-06-16-ui-item-slot-icon-dragdrop-spine-deep-dive.md`.
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## Retail anchors
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- `IconData::RenderIcons` @ `0x0058d180`
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(`named-retail/acclient_2013_pseudo_c.txt:407524`)
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- `UIElement_ItemList::PrepareDragIcon` @ `0x004e2a50`
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(`named-retail/acclient_2013_pseudo_c.txt:230765`)
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- `UIElement_ItemList::ItemList_BeginDrag` @ `0x004e32d0`
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(`named-retail/acclient_2013_pseudo_c.txt:231350`)
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- `UIElement_UIItem::SetWaitingState` @ `0x004e11b0`
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(`named-retail/acclient_2013_pseudo_c.txt:229190`)
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- `ACCWeenieObject::SetWaitingState` @ `0x0058c0d0`
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(`named-retail/acclient_2013_pseudo_c.txt:406260`)
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- `UIElement_UIItem` layout child `m_elem_Icon_Ghosted = 0x10000349`;
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the shared UIItem catalog `0x21000037` gives it DirectState surface
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`0x0600109A`.
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The live DAT catalog and the named retail code agree. The in-tree WorldBuilder
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reference has no retained UI/item-list implementation to compare for this path.
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## Literal pseudocode
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```text
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IconData.RenderIcons(item):
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destroy old m_pIcon and m_pDragIcon
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dragSurface = transparent 32 x 32
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blit item.baseIcon onto dragSurface using normal blit
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blit item.customOverlay onto dragSurface using alpha blit
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replace pure-white dragSurface pixels from the effect-color surface
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m_pDragIcon = Graphic(dragSurface)
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cellSurface = transparent 32 x 32
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blit typeDefaultUnderlay onto cellSurface using normal blit
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blit item.customUnderlay onto cellSurface using alpha blit
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blit dragSurface onto cellSurface using alpha blit
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m_pIcon = Graphic(cellSurface)
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ItemList.PrepareDragIcon(cell):
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clear cell.m_dragIcon image
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object = GetWeenieObject(cell.itemID)
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set cell.m_dragIcon image to object.GetDragIcon() # m_pDragIcon, not m_pIcon
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ItemList.ItemList_BeginDrag(cell):
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if PrepareDragIcon(cell) failed:
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return
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if cell is not selected:
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SetSelectedObject(cell.itemID, false)
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if list is not vendor, salvage, or shortcut list:
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cell.SetWaitingState(true)
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StartDragAndDrop(cell.m_dragIcon, hotspot = 16,16)
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UIItem.SetWaitingState(waiting):
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object.SetWaitingState(waiting)
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if cell is not unghostable:
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set m_elem_Icon_Ghosted visible = waiting
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on drag release/cancel:
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clear source waiting state
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hide m_elem_Icon_Ghosted
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```
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## Destination feedback and source overlay order
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`UIElement_ItemList::ItemList_DragOver @ 0x004e3400` distinguishes an ordinary
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slot insertion from dropping into a container:
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```text
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if target list is a container selector
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and target cell is occupied by a container
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and that container has an empty item slot:
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target.SetDragAcceptState(0x10000046) # ItemSlot_DragOver_DropIn
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# 0x060011F7 green arrow
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else if target accepts an ordinary item-list placement:
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target.SetDragAcceptState(0x10000041) # ItemSlot_DragOver_Accept
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# 0x060011F9 green circle
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else:
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target.SetDragAcceptState(0x10000040) # 0x060011F8 reject
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```
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Therefore the backpack contents grid uses the green circle; the side-bag column
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and main-pack container cell use the green drop-in arrow. The selected/open
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indicators remain visible while `m_elem_Icon_Ghosted` is active, so the
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procedural leaf draws the waiting mesh before those persistent indicators and
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keeps drag-accept feedback topmost.
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## Port mapping
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- `IconComposer` caches the underlay-free composite separately and exposes
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`GetDragIcon`; the ordinary `GetIcon` still layers the two underlays beneath
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the same cached drag pixels.
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- `UiItemSlot` stores `IconTexture` and `DragIconTexture` separately.
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`GetDragGhost` returns the latter, while `OnDraw` keeps the former in the
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source cell.
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- `UiRoot` owns the generic source-active lifecycle, including release outside
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UI and source-subtree removal. It dispatches `DragBegin` before enabling the
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source-active mesh, matching retail's select-then-waiting order. The inventory,
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paperdoll, and toolbar handlers select an unselected dragged item synchronously.
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`UiItemSlot` maps the lifecycle to the retail waiting visual for physical lists;
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shortcut aliases remain unghosted.
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- `UiItemSlot.WaitingSprite` is the authored `0x0600109A` mesh, not a procedural
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tint.
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## Conformance coverage
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- `DragDropSpineTests.GetDragGhost_prefersDedicatedUnderlayFreeTexture`
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- `DragDropSpineTests.InventoryDrag_ghostsSourceUntilRelease`
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- `InventoryControllerTests.OnDragLift_selectsItem_butKeepsItUntilServerConfirms`
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- `PaperdollControllerTests.DragLift_selectsEquippedItem_beforeWaitingVisual`
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- `DragDropSpineTests.ShortcutDrag_doesNotGhostSource`
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- `UiItemSlotTests.DefaultWaitingSprite_isRetailGhostMesh`
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- `InventoryControllerTests.Empty_sprites_and_drop_feedback_are_applied_per_list_role`
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- Existing `IconComposerTests.TwoStageWithEffect_copiesTilePixelBeforeUnderlay`
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locks the two-stage composition order.
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