# Retail inventory listbox scrolling pseudocode

## Named-retail anchors

- `UIElement_ListBox::ScrollToY @ 0x0046D550`
- `UIElement_ListBox::InqScrollDelta @ 0x0046DC10`
- `UIElement_ListBox::ScrollToView @ 0x0046E9F0`
- `UIElement_Scrollable::SetScrollableXY @ 0x004740C0`
- `UIElement_ItemList::ItemList_SetParentContainer @ 0x004E49D0`
- `UIElement_ItemList::RefreshList @ 0x004E4C00`

## Scroll model

```text
ScrollToY(pixelY):
    SetScrollableXY(currentX, pixelY, false)

InqScrollDelta(vertical, negativeDirection, page):
    if page:
        delta = viewportHeight
    else if rowCount != 0:
        delta = min(scrollableHeight / rowCount, viewportHeight)
    else:
        delta = 0
    return negativeDirection ? -delta : delta
```

The stored position is an integer pixel coordinate, not a row index. Scrollbar
thumb movement can therefore stop with a row partially visible. Wheel/arrow line
steps remain one row high because `InqScrollDelta` derives the line delta from
`scrollableHeight / rowCount`.

`ScrollToView(index)` sums preceding row heights and compares that pixel rectangle
against `[scrollY, scrollY + viewportHeight]`; it adjusts only when the item lies
outside the visible pixel interval.

## Refresh behavior

```text
RefreshList():
    ItemList_SetParentContainer(parentContainerID, refresh=true, notify=true)

ItemList_SetParentContainer(...):
    update capacity
    flush item elements
    add current contained objects in order
    // no ScrollToHome / SetScrollableXY(0) in this path
```

The item-element rebuild does not explicitly home the list. A client-side retained
rebuild must therefore preserve `m_iScrollableY` and clamp it only after the complete
replacement content establishes its final extent.

## acdream port shape

- `UiItemList.DeferLayout` prevents transient one-cell extents from clamping the
  retained pixel offset during `InventoryController.Populate`.
- Intersecting edge cells remain visible at their true `rowY - ScrollY` coordinate.
- `UiElement.ClipsChildren` pushes a nested screen-space clip; `UiRenderContext`
  crops sprite geometry and matching UVs, so a partial row paints only inside the
  contents viewport and cannot receive input outside it.
- The inventory window's maximum height is the available screen height rather than
  the former arbitrary 560 px cap. Exact keystone resize bounds remain AP-54.