15aa3b9aff
Preserve pixel scroll offsets across inventory rebuilds, crop partially visible rows with nested geometry/UV clips, and replace the obsolete 560px resize ceiling with available screen height. Keep retail's row-sized wheel step while allowing continuous scrollbar thumb positions. Co-Authored-By: Codex <codex@openai.com>
63 lines
2.3 KiB
Markdown
63 lines
2.3 KiB
Markdown
# Retail inventory listbox scrolling pseudocode
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## Named-retail anchors
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- `UIElement_ListBox::ScrollToY @ 0x0046D550`
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- `UIElement_ListBox::InqScrollDelta @ 0x0046DC10`
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- `UIElement_ListBox::ScrollToView @ 0x0046E9F0`
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- `UIElement_Scrollable::SetScrollableXY @ 0x004740C0`
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- `UIElement_ItemList::ItemList_SetParentContainer @ 0x004E49D0`
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- `UIElement_ItemList::RefreshList @ 0x004E4C00`
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## Scroll model
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```text
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ScrollToY(pixelY):
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SetScrollableXY(currentX, pixelY, false)
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InqScrollDelta(vertical, negativeDirection, page):
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if page:
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delta = viewportHeight
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else if rowCount != 0:
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delta = min(scrollableHeight / rowCount, viewportHeight)
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else:
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delta = 0
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return negativeDirection ? -delta : delta
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```
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The stored position is an integer pixel coordinate, not a row index. Scrollbar
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thumb movement can therefore stop with a row partially visible. Wheel/arrow line
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steps remain one row high because `InqScrollDelta` derives the line delta from
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`scrollableHeight / rowCount`.
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`ScrollToView(index)` sums preceding row heights and compares that pixel rectangle
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against `[scrollY, scrollY + viewportHeight]`; it adjusts only when the item lies
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outside the visible pixel interval.
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## Refresh behavior
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```text
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RefreshList():
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ItemList_SetParentContainer(parentContainerID, refresh=true, notify=true)
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ItemList_SetParentContainer(...):
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update capacity
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flush item elements
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add current contained objects in order
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// no ScrollToHome / SetScrollableXY(0) in this path
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```
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The item-element rebuild does not explicitly home the list. A client-side retained
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rebuild must therefore preserve `m_iScrollableY` and clamp it only after the complete
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replacement content establishes its final extent.
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## acdream port shape
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- `UiItemList.DeferLayout` prevents transient one-cell extents from clamping the
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retained pixel offset during `InventoryController.Populate`.
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- Intersecting edge cells remain visible at their true `rowY - ScrollY` coordinate.
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- `UiElement.ClipsChildren` pushes a nested screen-space clip; `UiRenderContext`
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crops sprite geometry and matching UVs, so a partial row paints only inside the
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contents viewport and cannot receive input outside it.
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- The inventory window's maximum height is the available screen height rather than
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the former arbitrary 560 px cap. Exact keystone resize bounds remain AP-54.
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