Crate virtualizer 

A headless virtualization engine inspired by TanStack Virtual.

For adapter-level utilities (anchoring, tweens), see the virtualizer-adapter crate.

This crate focuses on the core algorithms needed to render massive lists at interactive frame rates: prefix sums over item sizes, fast offset → index lookup, overscanned visible ranges, and optional dynamic measurement.

It is UI-agnostic. A TUI/GUI layer is expected to provide:

• viewport size (height/width)
• scroll offset
• item size estimates and (optionally) dynamic measurements

Feature flags

• std (default): Enables std support.
• serde: Adds serde::Serialize/Deserialize for the public data types (ranges/items/state).
• tracing: Emits internal trace/debug/warn events via tracing (requires std).

Structs

FrameState

A combined snapshot of viewport + scroll state.

IndexEmitter

Helper to build correct range_extractor implementations without allocations.

Range

The input range passed to a crate::RangeExtractor.

Rect

A platform-agnostic viewport rect.

ScrollState

A lightweight, serializable snapshot of the current scroll state.

ViewportState

A lightweight, serializable snapshot of the current viewport geometry.

VirtualItem

A virtual item produced for rendering.

VirtualItemKeyed

A virtual item that carries its stable key.

VirtualRange

A half-open range of virtual item indexes: [start_index, end_index).

Virtualizer

A headless virtualization engine.

VirtualizerOptions

Configuration for crate::Virtualizer.

Enums

Align

Alignment used by scroll-to helpers.

InitialOffset

Initial scroll offset configuration.

ScrollDirection

Scroll direction derived from the latest scroll offset update.

Type Aliases

ItemKey

Default item key type (index-based).

OnChangeCallback

A callback fired when a virtualizer state update occurs.

RangeExtractor

A callback that emits virtual item indexes for a given visible range.

ShouldAdjustScrollPositionOnItemSizeChangeCallback

A hook that decides whether to adjust scroll position when an item size changes.