Virtualize

1export type MeasureStrategy =
2  | FixedStrategy
3  | CappedStrategy
4  | ComputedStrategy
5 
6// Height is always the same regardless of content or width.
7// Examples: buttons, pills, status indicators, headers.
8export type FixedStrategy = {
9  kind: 'fixed'
10  height: number
11}
12 
13// Content scrolls inside a capped container.
14// Height is min(estimatedContent, maxHeight).
15// Examples: JSON preview, log viewer, reasoning block.
16export type CappedStrategy = {
17  kind: 'capped'
18  maxHeight: number
19  // If you can estimate content height cheaply (e.g. lineCount * lineHeight),
20  // provide it. Otherwise the cap is used as the height.
21  estimateContent?: number
22}
23 
24// Height is deterministic from props — pure arithmetic, no DOM.
25// Examples: list of N items × row height, grid of N columns.
26export type ComputedStrategy = {
27  kind: 'computed'
28  measure: (width: number) => number
29}
30 
31// --- Virtualisable item ---
32 
33export type VirtualItem<T = unknown> = {
34  id: string | number
35  strategy: MeasureStrategy
36  data: T
37}
38 
39// --- Resolved item (after measurement) ---
40 
41export type PositionedItem<T = unknown> = {
42  id: string | number
43  data: T
44  height: number
45  y: number
46}