VirtualGrid

VirtualGrid virtualizes a vertically scrolling grid.

Resolve columns from available width

VirtualGrid(items, [](const Item& item) {
  return ItemCard(item).Key(item.id);
})
    .Columns(GridColumns::Adaptive(220.0F))
    .EstimatedRowExtent(180.0F)
    .ColumnSpacing(16.0F)
    .RowSpacing(16.0F)
    .CacheExtent(320.0F)

Choose GridColumns::Fixed(count) for a stable column count or GridColumns::Adaptive(minimum_width) to resolve as many columns as available width can support.

Tune rows and spans

.RowExtent(...) describes fixed-height rows. Use .EstimatedRowExtent(...) when rows can vary. .ItemSpans(...) supplies the number of columns consumed by each corresponding item.

The same range, state range, and count-factory constructors as VirtualList are available. .Controller(...) supports metrics and indexed scrolling.

Preserve grid semantics

VirtualGrid publishes grid, row and column counts, and realized cell coordinates through accessibility semantics.

API

• Constructors inherited from VirtualLayout.
• Fluent methods: .Columns, .RowExtent, .EstimatedRowExtent, .RowSpacing, .ColumnSpacing, .CacheExtent, .ItemSpans, .Controller.
• Column model: GridColumns::Fixed or GridColumns::Adaptive.

Use Flow for a small wrapping collection that should mount every child.

Every sizing operation

Method	Contract
Columns(GridColumns)	Fixed(count) requires a positive count; Adaptive(minimum_width) requires positive width.
RowExtent(float)	Positive fixed row height.
EstimatedRowExtent(float)	Positive initial estimate when measured row heights vary.
RowSpacing(float), ColumnSpacing(float)	Nonnegative logical-pixel gaps.
CacheExtent(float)	Nonnegative offscreen realization distance.
ItemSpans(vector<size_t>)	Positive spans corresponding to logical items; each clamps to the resolved column count.
Controller(ScrollController)	Stable metrics and item-targeted scrolling.

GridColumns::Resolve(available_width, spacing) returns the resolved count for a proposed width; ordinary applications can let the grid perform this calculation. Adaptive columns respond to the grid’s actual constrained width, so the same declaration works inside a drawer or a main content area.

VirtualGrid scrolls vertically; it does not expose ScrollAxis. Supply a bounded height. A row is measured as a row, so a tall cell affects its neighboring cells’ vertical placement. Use a fixed RowExtent only when that rule matches every cell. Application data and persistent selection should live outside evictable cell scopes, as with VirtualList.