Flyweight grid: 20,000,000 cells
Ground truth lives in columnar typed arrays; rendered cells are disposable flyweight facades created per render pass; a sparse reactive overlay materializes per observation and evicts with the viewport. ~55% of cells hold real Excel-syntax formulas. Everything costs proportional to what is observed — never to what exists.
Nothing downloads until you click — the model code and the formula parser load on demand, then one more click creates all 20,000,000 cells in your browser.
What to notice
- Creation fills ~95 MB of typed arrays — not 20 million objects. The reactive layer allocates only for cells something actually observes.
- Edit a cell at row 1,000,000 and the column totals react — the dependency graph is discovered per observation, not precomputed.
- The measured protocol, numbers and design live in
RESULTS.mdandDESIGN.md; the deeper story is in Flyweight Pattern guide.
Related guide pages
- Flyweight Pattern — ground truth in plain storage, reactivity as an overlay.
- Keyed Version Signals — invalidation by key at scale.
- Static() — Capability Classes — capability classes,
$-cached statics, the anchor. - Performance by Design — what the shape costs and does not.
The source
The heart of the pattern — the sheet (columnar ground truth + sparse overlay) and the cell facade:
ts
/**
* FlyweightCell — the disposable facade. THREE fields; everything else is
* plain getters delegating to the sheet's tracked accessors, so:
*
* - construction allocates one near-empty object (ivue runs nothing at
* `new`, and plain getters de-optimize to native prototype getters);
* - reads are tracked through whatever effect performs them — a facade in
* a template subscribes the component exactly like a real cell would;
* - the reactive state lives on the SHEET's sparse overlay, so facades are
* created per render and dropped on scroll with zero loss.
*
* The reference `FormulaCell` (demo/formula) holds its own ref + computed;
* this holds NOTHING — that is the flyweight move.
*/
import { Reactive } from '../../../ivue';
import { FlyweightLogic } from '../FlyweightLogic';
import type { FlyweightSheet } from './FlyweightSheet';
class $FlyweightCell {
constructor(sheet: FlyweightSheet.Model, row: number, col: number) {
this.sheet = sheet;
this.row = row;
this.col = col;
}
readonly sheet: FlyweightSheet.Model;
readonly row: number;
readonly col: number;
/** Resolved value — tracked point read through the sheet. */
get value(): FlyweightLogic.CellValue {
return this.sheet.valueAt(this.row, this.col);
}
/** The literal text (formula source / number text). */
get source(): string {
return this.sheet.sourceAt(this.row, this.col);
}
get isFormula(): boolean {
return this.sheet.kindAt(this.row, this.col) === FlyweightLogic.Kind.Formula;
}
get display(): string {
return FlyweightLogic.Class.displayOf(this.value);
}
get cssClass(): string {
return FlyweightLogic.Class.cssOf(this.value, this.isFormula);
}
write(input: string): void {
this.sheet.write(this.row, this.col, input);
}
}
export namespace FlyweightCell {
export const $Class = $FlyweightCell;
export let Class = Reactive($Class);
export type Model = InstanceType<typeof Class>; // raw-instance type — collections, parameters, returns
export type Instance = typeof Class.Instance;
}ts
/**
* FlyweightSheet — 20M cells with NO cell objects at rest.
*
* Ground truth is columnar (`kind` Uint8Array + lazily-allocated Float64Array
* per column + a sparse Map for text/edited-formula sources). Reactivity is a
* SPARSE OVERLAY that materializes per observation:
*
* - fine tier — a version ref per OBSERVED cell (rendered / onCell /
* small range). Precise: conditional dependencies shift.
* - coarse tier — a version ref per 4,096-row BLOCK, subscribed only by
* LARGE ranges. =SUM(A1:A1000000) costs 245 edges, not 1M.
* - formula computeds — cached on demand; each carries ONE sync watcher
* (the derived-write bridge) that bumps its own block when
* its value changes, so coarse subscribers see through
* formulas — including their out-of-range inputs.
*
* Writes are O(observers-of-that-cell): update the arrays, bump the fine ref
* IF IT EXISTS and the block ref IF IT EXISTS (peek-only). A write to a
* never-observed cell allocates nothing and notifies no one.
*
* The dependency graph is still DISCOVERED, never hand-built — the same
* onCell/onRange seam as the formula grid (reference: demo/formula/Sheet.ts),
* with the parser reading through this sheet's tracked accessors.
*/
import FormulaParser from 'fast-formula-parser';
import { pauseTracking, resetTracking } from '@vue/reactivity';
import { computed, ref, watch, type ComputedRef, type Ref, type WatchStopHandle } from 'vue';
import { Reactive } from '../../../ivue';
import { Static } from '../../../Static';
import { FlyweightLogic } from '../FlyweightLogic';
class $FlyweightSheet {
/** The parser's error class, read off the parser module once per class —
* a static so a subclass can substitute the error shape it evaluates to. */
protected static get $FormulaError() {
return (
FormulaParser as unknown as {
FormulaError: new (error: string, details?: unknown) => FlyweightLogic.CellValue;
}
).FormulaError;
}
constructor(rows: number, cols: number = FlyweightLogic.Class.COLS) {
this.rows = rows;
this.cols = cols;
this.blockCount = Math.ceil(rows / this.Logic.BLOCK_ROWS);
// Hoist the METHODS once for the seeding loop (a late read of the
// mutable slot, so a subclass swap is still honored). Static()'s
// bound functions are exactly plain-function speed — the per-call
// cost is the ACCESSOR, so read it once per method, not 9M times.
// Measured in-browser on this loop (fresh-page medians):
// hoisted bound methods ......... plain-function speed (~30ms/9M)
// Logic.method() per call ....... ~85ms/9M (accessor each call)
const { isDataCol, numDataValue } = this.Logic;
// Seed the columnar ground truth. Data columns fill Float64Arrays
// numerically (no string round-trips — this is the whole creation cost);
// formula columns are a single Uint8Array.fill.
const columns: FlyweightSheet.Column[] = new Array(cols);
for (let col = 0; col < cols; col++) {
const kind = new Uint8Array(rows);
let numbers: Float64Array | null = null;
if (isDataCol(col)) {
numbers = new Float64Array(rows);
for (let row = 0; row < rows; row++) {
const value = numDataValue(row, col);
if (value !== null) {
kind[row] = FlyweightLogic.Kind.Number;
numbers[row] = value;
} // blanks stay FlyweightLogic.Kind.Blank
}
} else {
kind.fill(FlyweightLogic.Kind.Formula);
}
columns[col] = { kind, numbers, text: new Map() };
}
this.columns = columns;
this.parser = new FormulaParser({
onCell: (cellRef) => this.pointValue(cellRef.row, cellRef.col),
onRange: (rangeRef) => this.rangeValues(rangeRef as FlyweightSheet.RangeRef)
});
}
readonly rows: number;
readonly cols: number;
// --- ground truth (plain, non-reactive) ---
protected readonly columns: FlyweightSheet.Column[];
// --- the sparse reactive overlay (empty until observed) ---
protected readonly cellVersions = new Map<number, Ref<number>>();
protected readonly blockVersions = new Map<number, Ref<number>>();
protected readonly formulaCache = new Map<number, FlyweightSheet.FormulaEntry>();
protected readonly adHocCache = new Map<string, ComputedRef<FlyweightLogic.CellValue>>();
/** Blocks per column (fine↔coarse key math). */
protected readonly blockCount: number;
/** ONE parser for the whole sheet (reference: formula grid). */
protected readonly parser: FormulaParser;
/** Cycle guard — a cell re-entered mid-evaluation is a cycle → #REF!. */
protected readonly evaluating = new Set<number>();
/** When non-null, tracked reads record (row,col) — dep tracing. */
protected readonly trace = { recording: null as Array<[number, number]> | null };
/** The logic seam. A subclass overrides THIS to swap the whole config/
* mapping layer (`protected override get Logic() { return
* WideGridLogic.Class }`) — every read below, including the seeding
* loop's one-time destructure, follows the override. A single read
* costs one tracked getter call; only PER-CALL reads in the 9M-loop
* were ever a cost, and the destructure below avoids exactly that. */
protected get Logic() {
return FlyweightLogic.Class;
}
/** The one cast per class: instance code reads its own statics here. */
protected get self() {
return this.constructor as typeof $FlyweightSheet;
}
// --- keys ---
protected cellKey(row: number, col: number): number {
return col * this.rows + row;
}
protected blockKey(row: number, col: number): number {
return col * this.blockCount + (row >> this.Logic.BLOCK_SHIFT);
}
// --- version-ref plumbing ---
/** Subscribe the current effect to a cell (get-OR-CREATE — observation). */
protected trackCell(row: number, col: number): void {
const cellKey = this.cellKey(row, col);
let versionRef = this.cellVersions.get(cellKey);
if (!versionRef) {
versionRef = ref(0);
this.cellVersions.set(cellKey, versionRef);
}
void versionRef.value;
}
/** Subscribe the current effect to a block (get-or-create — observation). */
protected trackBlock(blockKey: number): void {
let versionRef = this.blockVersions.get(blockKey);
if (!versionRef) {
versionRef = ref(0);
this.blockVersions.set(blockKey, versionRef);
}
void versionRef.value;
}
/** Notify a cell's observers — PEEK-ONLY (unobserved cells cost nothing). */
protected bumpCell(row: number, col: number): void {
const versionRef = this.cellVersions.get(this.cellKey(row, col));
if (versionRef) versionRef.value++;
}
/** Notify a block's observers — peek-only. */
protected bumpBlock(row: number, col: number): void {
const versionRef = this.blockVersions.get(this.blockKey(row, col));
if (versionRef) versionRef.value++;
}
// --- raw reads ---
/** UNTRACKED ground-truth value (blank→null). No refs, no observation. */
rawAt(row: number, col: number): FlyweightLogic.CellValue {
const column = this.columns[col];
switch (column.kind[row]) {
case FlyweightLogic.Kind.Number:
return column.numbers![row];
case FlyweightLogic.Kind.Text:
return column.text.get(row) ?? '';
case FlyweightLogic.Kind.Formula:
return this.sourceAt(row, col); // raw view of a formula = its source
default:
return null;
}
}
/** The literal text of a cell (formula source / number text / text). */
sourceAt(row: number, col: number): string {
const column = this.columns[col];
const override = column.text.get(row);
if (override !== undefined) return override;
switch (column.kind[row]) {
case FlyweightLogic.Kind.Number:
return String(column.numbers![row]);
case FlyweightLogic.Kind.Formula:
return this.Logic.patternSource(row, col) ?? '';
default:
return '';
}
}
kindAt(row: number, col: number): FlyweightLogic.Kind {
return this.columns[col].kind[row] as FlyweightLogic.Kind;
}
// --- tracked reads ---
/**
* The TRACKED point read — what rendered cells, facades and onCell use.
* Formula cells resolve through their cached computed (which carries its
* own fine ref for source edits); everything else takes a fine ref here.
*/
valueAt(row: number, col: number): FlyweightLogic.CellValue {
if (row < 0 || row >= this.rows || col < 0 || col >= this.cols) return null;
if (this.columns[col].kind[row] === FlyweightLogic.Kind.Formula) {
return this.formulaValue(row, col).value;
}
this.trackCell(row, col);
return this.rawAt(row, col);
}
/** onCell seam (1-based, like the parser). */
protected pointValue(oneBasedRow: number, oneBasedCol: number): FlyweightLogic.CellValue {
if (this.trace.recording) this.trace.recording.push([oneBasedRow, oneBasedCol]);
return this.valueAt(oneBasedRow - 1, oneBasedCol - 1);
}
/**
* onRange seam. Small ranges read per-cell (fine tier — precise).
* Large ranges subscribe BLOCKS, then read ground truth with tracking
* PAUSED; formula cells inside resolve through their cached computeds
* (transitive observation, priced) whose derived-write watchers keep the
* block tier truthful.
*/
protected rangeValues(range: FlyweightSheet.RangeRef): FlyweightLogic.CellValue[][] {
const startRow = range.from.row - 1;
const startCol = range.from.col - 1;
const endRow = Math.min(range.to.row - 1, this.rows - 1);
const endCol = Math.min(range.to.col - 1, this.cols - 1);
const cellCount = (endRow - startRow + 1) * (endCol - startCol + 1);
if (this.trace.recording) {
for (let row = startRow; row <= endRow; row++)
for (let col = startCol; col <= endCol; col++)
this.trace.recording.push([row + 1, col + 1]);
}
const values: FlyweightLogic.CellValue[][] = [];
if (cellCount <= this.Logic.FINE_RANGE_LIMIT) {
for (let row = startRow; row <= endRow; row++) {
const rowValues: FlyweightLogic.CellValue[] = [];
for (let col = startCol; col <= endCol; col++) rowValues.push(this.valueAt(row, col));
values.push(rowValues);
}
return values;
}
// Coarse tier: subscribe every covered block (tracked), …
const firstBlock = startRow >> this.Logic.BLOCK_SHIFT;
const lastBlock = endRow >> this.Logic.BLOCK_SHIFT;
for (let col = startCol; col <= endCol; col++) {
for (let block = firstBlock; block <= lastBlock; block++) {
this.trackBlock(col * this.blockCount + block);
}
}
// …then read with tracking paused (no fine edges from this range).
pauseTracking();
try {
for (let row = startRow; row <= endRow; row++) {
const rowValues: FlyweightLogic.CellValue[] = [];
for (let col = startCol; col <= endCol; col++) {
rowValues.push(
this.columns[col].kind[row] === FlyweightLogic.Kind.Formula
? this.formulaValue(row, col).value
: this.rawAt(row, col)
);
}
values.push(rowValues);
}
} finally {
resetTracking();
}
return values;
}
// --- formulas ---
/**
* The cached computed for a formula cell — created on first observation.
* THIN on purpose: the computed and watcher bodies are small pointers to
* named, directly testable methods on the prototype.
*/
protected formulaValue(row: number, col: number): ComputedRef<FlyweightLogic.CellValue> {
const cellKey = this.cellKey(row, col);
let entry = this.formulaCache.get(cellKey);
if (!entry) {
const value = computed<FlyweightLogic.CellValue>(() => this.evaluateCell(row, col));
const stopBridge = watch(
value,
(newValue, oldValue) => this.onFormulaValueChanged(row, col, newValue, oldValue),
{ flush: 'sync' }
);
entry = { value, stopBridge };
this.formulaCache.set(cellKey, entry);
}
return entry.value;
}
/**
* The DERIVED-WRITE BRIDGE: when a formula's value changes, bump the
* cell's block so coarse subscribers invalidate even though the
* underlying write happened somewhere else entirely.
*/
protected onFormulaValueChanged(
row: number,
col: number,
newValue: FlyweightLogic.CellValue,
oldValue: FlyweightLogic.CellValue
): void {
if (newValue !== oldValue) this.bumpBlock(row, col);
}
/** Evaluate a cell by its CURRENT kind (formulas through the parser). */
protected evaluateCell(row: number, col: number): FlyweightLogic.CellValue {
// Source edits / kind flips invalidate this computed via the fine ref.
this.trackCell(row, col);
const kind = this.columns[col].kind[row];
if (kind !== FlyweightLogic.Kind.Formula) return this.rawAt(row, col);
const source = this.sourceAt(row, col);
const body = this.Logic.stripFormula(source);
if (body.trim().length === 0) return null;
const cellKey = this.cellKey(row, col);
if (this.evaluating.has(cellKey)) return new this.self.$FormulaError('#REF!');
this.evaluating.add(cellKey);
try {
// COLUMNAR FAST PATH: a bare aggregate over one range is computed
// linearly over ground truth with the SAME reactive semantics (fine
// tier small / block tier large, formulas via cached computeds). The
// general parser's range aggregation is O(n²) in range size —
// measured 27ms @ 10k cells → 40s @ 200k — so bulk aggregation
// belongs to the columnar layer, exactly as desktop engines
// special-case their range ops.
const aggregate = this.Logic.matchSimpleAggregate(body);
if (aggregate) return this.fastAggregate(aggregate);
return this.parser.parse(body, {
row: row + 1,
col: col + 1,
sheet: 'Sheet1'
}) as FlyweightLogic.CellValue;
} catch (error) {
return error instanceof (this.self.$FormulaError as unknown as Function)
? (error as FlyweightLogic.CellValue)
: new this.self.$FormulaError('#ERROR!');
} finally {
this.evaluating.delete(cellKey);
}
}
/**
* A live ad-hoc formula over the sheet (the demo's totals bar) — a cached
* computed evaluating `body` through the same parser/seams, so a large
* range inside it costs blocks, not cells. Thin: the computed is a pointer
* to the named, directly testable evaluateAdHocFormula method.
*/
liveFormula(body: string): ComputedRef<FlyweightLogic.CellValue> {
let cached = this.adHocCache.get(body);
if (!cached) {
cached = computed<FlyweightLogic.CellValue>(() => this.evaluateAdHocFormula(body));
this.adHocCache.set(body, cached);
}
return cached;
}
protected evaluateAdHocFormula(body: string): FlyweightLogic.CellValue {
try {
const aggregate = this.Logic.matchSimpleAggregate(body);
if (aggregate) return this.fastAggregate(aggregate);
return this.parser.parse(body, {
row: 1,
col: 1,
sheet: 'Sheet1'
}) as FlyweightLogic.CellValue;
} catch (error) {
return error instanceof (this.self.$FormulaError as unknown as Function)
? (error as FlyweightLogic.CellValue)
: new this.self.$FormulaError('#ERROR!');
}
}
/**
* Linear aggregation over a range with the same observation semantics as
* rangeValues: small ranges take fine per-cell tracking, large ranges take
* block subscriptions + paused reads (formula cells through their cached
* computeds; the derived-write bridge keeps blocks truthful). Numbers
* aggregate; blanks/text are skipped (COUNT counts numbers, Excel-style);
* an error value propagates.
*/
protected fastAggregate(aggregate: FlyweightLogic.SimpleAggregate): FlyweightLogic.CellValue {
const startRow = aggregate.startRow - 1;
const startCol = aggregate.startCol - 1;
const endRow = Math.min(aggregate.endRow - 1, this.rows - 1);
const endCol = Math.min(aggregate.endCol - 1, this.cols - 1);
const cellCount = (endRow - startRow + 1) * (endCol - startCol + 1);
const isFineTier = cellCount <= this.Logic.FINE_RANGE_LIMIT;
if (!isFineTier) {
const firstBlock = startRow >> this.Logic.BLOCK_SHIFT;
const lastBlock = endRow >> this.Logic.BLOCK_SHIFT;
for (let col = startCol; col <= endCol; col++) {
for (let block = firstBlock; block <= lastBlock; block++) {
this.trackBlock(col * this.blockCount + block);
}
}
pauseTracking();
}
try {
let sum = 0;
let count = 0;
let min = Infinity;
let max = -Infinity;
for (let col = startCol; col <= endCol; col++) {
const column = this.columns[col];
for (let row = startRow; row <= endRow; row++) {
let cellValue: FlyweightLogic.CellValue;
if (isFineTier) {
cellValue = this.valueAt(row, col);
} else if (column.kind[row] === FlyweightLogic.Kind.Formula) {
cellValue = this.formulaValue(row, col).value;
} else {
cellValue = this.rawAt(row, col);
}
if (typeof cellValue === 'number') {
sum += cellValue;
count++;
if (cellValue < min) min = cellValue;
if (cellValue > max) max = cellValue;
} else if (this.Logic.isFormulaError(cellValue)) {
return cellValue; // errors propagate, Excel-style
}
}
}
switch (aggregate.fn) {
case 'SUM':
return sum;
case 'AVERAGE':
return count === 0 ? new this.self.$FormulaError('#DIV/0!') : sum / count;
case 'COUNT':
return count;
case 'MIN':
return count === 0 ? 0 : min;
case 'MAX':
return count === 0 ? 0 : max;
default:
return new this.self.$FormulaError('#VALUE!'); // unreachable — union is exhaustive
}
} finally {
if (!isFineTier) resetTracking();
}
}
// --- writes ---
/**
* THE single write path. O(1) storage update + O(observers) notification.
* Never allocates reactive state (peek-only bumps).
*/
write(row: number, col: number, input: string): void {
const column = this.columns[col];
const trimmed = input.trim();
if (this.Logic.isFormulaText(input)) {
column.kind[row] = FlyweightLogic.Kind.Formula;
column.text.set(row, input);
} else if (trimmed.length === 0) {
column.kind[row] = FlyweightLogic.Kind.Blank;
column.text.delete(row);
} else {
const numeric = Number(trimmed);
if (!Number.isNaN(numeric) && Number.isFinite(numeric)) {
if (!column.numbers) column.numbers = new Float64Array(this.rows);
column.kind[row] = FlyweightLogic.Kind.Number;
column.numbers[row] = numeric;
column.text.delete(row);
} else {
column.kind[row] = FlyweightLogic.Kind.Text;
column.text.set(row, input);
}
}
this.bumpCell(row, col);
this.bumpBlock(row, col);
}
// --- diagnostics ---
/**
* Which cells does (row,col)'s formula CURRENTLY read? Re-parses once with
* the read-tap on — it walks the same onCell/onRange path Vue tracks, so
* the set IS the live dependency set (and visibly SHIFTS across an IF's
* branch boundary). 1-based in/out, like the formula grid's traceDeps.
*/
traceDeps(oneBasedRow: number, oneBasedCol: number): Array<[number, number]> {
const row = oneBasedRow - 1;
const col = oneBasedCol - 1;
if (this.columns[col]?.kind[row] !== FlyweightLogic.Kind.Formula) return [];
const body = this.Logic.stripFormula(this.sourceAt(row, col));
if (body.trim().length === 0) return [];
const previousTracer = this.trace.recording;
this.trace.recording = [];
pauseTracking();
try {
this.parser.parse(body, {
row: oneBasedRow,
col: oneBasedCol,
sheet: 'Sheet1'
});
} catch {
/* keep whatever reads happened before the error */
} finally {
resetTracking();
}
const recorded = this.trace.recording;
this.trace.recording = previousTracer;
const seenKeys = new Set<number>();
const dependencies: Array<[number, number]> = [];
for (const [row1, col1] of recorded) {
const dedupeKey = row1 * (this.cols + 1) + col1;
if (!seenKeys.has(dedupeKey)) {
seenKeys.add(dedupeKey);
dependencies.push([row1, col1]);
}
}
return dependencies;
}
/** The observation census — the law, measurable. */
stats() {
return {
fineRefs: this.cellVersions.size,
blockRefs: this.blockVersions.size,
formulaComputeds: this.formulaCache.size,
adHocFormulas: this.adHocCache.size
};
}
/**
* Release a formula cell's cached computed (stops its derived-write
* watcher). Production ties this to viewport/refcount eviction — see
* DESIGN.md honest boundaries.
*/
releaseFormula(row: number, col: number): void {
const cellKey = this.cellKey(row, col);
const entry = this.formulaCache.get(cellKey);
if (entry) {
entry.stopBridge();
this.formulaCache.delete(cellKey);
}
}
/**
* Viewport-tied eviction: release overlay entries (fine refs + formula
* computeds) for all rows OUTSIDE [keepStart, keepEnd]. Row-scoped and
* column-agnostic. Block refs are kept (bounded: ≤ blockCount × cols).
*
* SAFETY relies on dependency LOCALITY: a released fine ref / computed
* must not have live dependents outside the kept range. In this layout
* the longest dependency reach is the running-sum chain (RUNSUM_BLOCK =
* 50 rows), so callers must keep a margin ≥ that around the viewport.
* A production impl replaces this with refcounts; documented boundary.
*
* Correctness after release is by re-materialization: the next
* observation of a released cell creates a fresh ref/computed over the
* unchanged ground truth.
*/
evictOutsideRows(keepStart: number, keepEnd: number): number {
let released = 0;
for (const [cellKey, entry] of this.formulaCache) {
const row = cellKey % this.rows;
if (row < keepStart || row > keepEnd) {
entry.stopBridge();
this.formulaCache.delete(cellKey);
released++;
}
}
for (const cellKey of this.cellVersions.keys()) {
const row = cellKey % this.rows;
if (row < keepStart || row > keepEnd) {
this.cellVersions.delete(cellKey);
released++;
}
}
return released;
}
/** Drop the entire overlay (watchers stopped). Ground truth untouched. */
releaseAll(): void {
for (const entry of this.formulaCache.values()) entry.stopBridge();
this.formulaCache.clear();
this.cellVersions.clear();
this.blockVersions.clear();
this.adHocCache.clear();
}
}
export namespace FlyweightSheet {
export const $Class = Static($FlyweightSheet); // anchor — it declares statics
export let Class = Reactive($Class);
export type Model = InstanceType<typeof Class>; // raw-instance type — collections, parameters, returns
export type Instance = typeof Class.Instance;
/* Types */
export interface RangeRef {
from: { row: number; col: number };
to: { row: number; col: number };
}
export interface Column {
kind: Uint8Array;
/** Allocated on the first numeric write — formula columns never pay. */
numbers: Float64Array | null;
/** Sparse: typed text AND user-edited formula sources (pattern overrides). */
text: Map<number, string>;
}
export interface FormulaEntry {
value: ComputedRef<FlyweightLogic.CellValue>;
/** Stops the derived-write bridge watcher (see formulaValue). */
stopBridge: WatchStopHandle;
}
}ts
/**
* Page controller for the flyweight grid, authored per the ivue operating
* manual. The composition-API version of this logic carried seven
* `computed()`s; under the doctrine exactly ONE survives (`visibleRows`,
* render suppression) — every other derivation is a plain getter at zero
* bytes per instance. The one computed is THIN: its body delegates to the
* directly testable `buildVisibleRows()` method.
*/
import {
computed,
getCurrentScope,
onMounted,
onScopeDispose,
ref,
shallowRef,
watch,
type ComputedRef
} from 'vue';
import { Reactive } from '../../ivue';
import { Static } from '../../Static';
import { FlyweightLogic } from './FlyweightLogic';
import { FlyweightCell } from './model/FlyweightCell';
import { FlyweightSheet } from './model/FlyweightSheet';
class $FlyweightGridPage {
/**
* Scroll has physical walls: Chrome's compositor does scroll math in
* FLOAT32 (dead past 2^24 = 16,777,216 px — a 28M px scroller stops at
* ~row 599,186); Firefox caps element height at ~17.9M px. Cap the
* physical height under both and map scroll ratio → virtual offset (the
* scaled scrollbar every big-grid engine uses; ~2.4:1 at 1M rows).
*/
protected static readonly MAX_SCROLL_HEIGHT = 12_000_000;
/** Eviction margin ≫ the 50-row running-sum reach (dependency locality). */
protected static readonly EVICT_MARGIN_ROWS = 512;
constructor() {
// Viewport-tied eviction, debounced so a fast flick doesn't thrash.
// Plain watch: the constructor runs in setup() context, so the
// component scope owns and stops it on unmount.
watch(
() => this.startRow,
() => this.scheduleEviction()
);
onMounted(() => {
this.timers.census = setInterval(() => this.pollCensus(), 500);
this.installHarness();
});
// Timers die with the component (watchers are component-scoped already).
if (getCurrentScope()) {
onScopeDispose(() => {
if (this.timers.census) clearInterval(this.timers.census);
if (this.timers.evict) clearTimeout(this.timers.evict);
});
}
}
/** The one cast per class: instance code reads its own statics here. */
protected get self() {
return this.constructor as typeof $FlyweightGridPage;
}
// --- state ---
get sheet() {
return shallowRef<FlyweightSheet.Model | null>(null);
}
get creationMs() {
return ref(0);
}
get scrollTop() {
return ref(0);
}
/** Template-ref target — destructured by the SFC for ref="scrollEl". */
get scrollEl() {
return ref<HTMLElement | null>(null);
}
get editing() {
return ref<{ row: number; col: number } | null>(null);
}
get draft() {
return ref('');
}
/** Polled diagnostics, not model state — refreshed on an interval. */
get census() {
return ref({
fineRefs: 0,
blockRefs: 0,
formulaComputeds: 0,
adHocFormulas: 0
});
}
// --- non-reactive infra (timers) ---
protected readonly timers = {
census: null as ReturnType<typeof setInterval> | null,
evict: null as ReturnType<typeof setTimeout> | null
};
// --- derived (plain getters) ---
get hasModel() {
return this.sheet.value !== null;
}
get modelCells() {
return this.sheet.value ? this.sheet.value.rows * FlyweightLogic.Class.COLS : 0;
}
get naturalHeight() {
return this.sheet.value ? this.sheet.value.rows * FlyweightLogic.Class.ROW_HEIGHT : 0;
}
get totalHeight() {
return Math.min(this.naturalHeight, this.self.MAX_SCROLL_HEIGHT);
}
get scrollScale() {
return this.naturalHeight > this.totalHeight
? (this.naturalHeight - FlyweightLogic.Class.VIEWPORT_HEIGHT) /
(this.totalHeight - FlyweightLogic.Class.VIEWPORT_HEIGHT)
: 1;
}
/** Position in CONTENT space (0 … naturalHeight − viewport). */
get virtualTop() {
return this.scrollTop.value * this.scrollScale;
}
get startRow() {
return Math.max(
0,
Math.floor(this.virtualTop / FlyweightLogic.Class.ROW_HEIGHT) - FlyweightLogic.Class.OVERSCAN
);
}
get endRow() {
const visibleCount = Math.ceil(
FlyweightLogic.Class.VIEWPORT_HEIGHT / FlyweightLogic.Class.ROW_HEIGHT
);
return this.sheet.value
? Math.min(
this.sheet.value.rows,
this.startRow + visibleCount + FlyweightLogic.Class.OVERSCAN * 2
)
: 0;
}
/** Pin the window band under the physical scroll position (degenerates
* to startRow × FlyweightLogic.Class.ROW_HEIGHT when scale = 1). */
get offsetY() {
return (
this.scrollTop.value - (this.virtualTop - this.startRow * FlyweightLogic.Class.ROW_HEIGHT)
);
}
/**
* The ONLY cell objects in existence — facades for the visible window.
* The one surgical computed() on this page: without the cache, the
* 500ms census poll would re-render the component and a plain getter
* would rebuild ~520 facades per poll; cached, an unchanged window
* returns the same array instance and the v-for never re-patches.
*/
// computed: render-suppression — see above
get visibleRows(): ComputedRef<FlyweightGridPage.PageRow[]> {
return computed(() => this.buildVisibleRows());
}
/** Live full-column totals (block tier: 245 edges each). liveFormula is
* cached on the sheet, so rebuilding this array per render is pointer
* work — a plain getter suffices. */
get totals(): { label: string; total: ComputedRef<FlyweightLogic.CellValue> }[] {
const sheet = this.sheet.value;
if (!sheet) return [];
const lastRow = sheet.rows;
return [
{
label: `SUM(A1:A${lastRow})`,
total: sheet.liveFormula(`SUM(A1:A${lastRow})`)
},
{
label: `AVERAGE(B1:B${lastRow})`,
total: sheet.liveFormula(`AVERAGE(B1:B${lastRow})`)
},
{
label: `SUM(D1:D${lastRow})`,
total: sheet.liveFormula(`SUM(D1:D${lastRow})`)
}
];
}
get activeRef() {
const editing = this.editing.value;
return editing ? FlyweightLogic.Class.colLabel(editing.col) + (editing.row + 1) : '';
}
get activeSource() {
const editing = this.editing.value;
return editing && this.sheet.value ? this.sheet.value.sourceAt(editing.row, editing.col) : '';
}
get activeRefLabel() {
return this.activeRef || 'fx';
}
get activeSourceLabel() {
return this.activeSource || 'click a cell to see + edit its formula';
}
get viewportStyle() {
return { height: `${this.totalHeight}px` };
}
get rowsStyle() {
return { transform: `translateY(${this.offsetY}px)` };
}
// --- methods ---
protected buildVisibleRows(): FlyweightGridPage.PageRow[] {
const sheet = this.sheet.value;
if (!sheet) return [];
const pageRows: FlyweightGridPage.PageRow[] = [];
for (let row = this.startRow; row < this.endRow; row++) {
const cells: FlyweightCell.Model[] = new Array(FlyweightLogic.Class.COLS);
for (let col = 0; col < FlyweightLogic.Class.COLS; col++)
cells[col] = new FlyweightCell.Class(sheet, row, col);
pageRows.push({ row, cells });
}
return pageRows;
}
createModel() {
this.editing.value = null;
const startedAt = performance.now();
const sheet = new FlyweightSheet.Class(FlyweightLogic.Class.ROWS_1M, FlyweightLogic.Class.COLS);
this.creationMs.value = performance.now() - startedAt;
this.sheet.value = sheet;
this.pollCensus();
// eslint-disable-next-line no-console
console.log(
`[flyweight] created ${(FlyweightLogic.Class.ROWS_1M * FlyweightLogic.Class.COLS).toLocaleString()} cells in ${this.creationMs.value.toFixed(1)}ms`
);
}
onScroll(event: Event) {
this.scrollTop.value = (event.target as HTMLElement).scrollTop;
}
/** Header label for a 1-based `v-for="column in COLS"` column. */
headerLabel(columnNumber: number) {
return FlyweightLogic.Class.colLabel(columnNumber - 1);
}
/** The 1-based, thousands-grouped row number the gutter shows. */
rowNumber(row: number) {
return (row + 1).toLocaleString();
}
isEditing(row: number, col: number) {
const editing = this.editing.value;
return !!editing && editing.row === row && editing.col === col;
}
edit(cell: FlyweightCell.Model) {
this.editing.value = { row: cell.row, col: cell.col };
this.draft.value = cell.source;
}
commitEdit() {
const editing = this.editing.value;
if (editing && this.sheet.value)
this.sheet.value.write(editing.row, editing.col, this.draft.value);
this.editing.value = null;
}
/** The edit's blur commits — its own handler, so a subclass can treat a
* blur apart from an Enter. */
onEditBlur() {
this.commitEdit();
}
/** Enter in the edit commits. */
onEditEnter() {
this.commitEdit();
}
pollCensus() {
const sheet = this.sheet.value;
if (sheet) this.census.value = sheet.stats();
}
scheduleEviction() {
if (this.timers.evict) clearTimeout(this.timers.evict);
this.timers.evict = setTimeout(() => {
const sheet = this.sheet.value;
if (!sheet) return;
sheet.evictOutsideRows(
Math.max(0, this.startRow - this.self.EVICT_MARGIN_ROWS),
this.endRow + this.self.EVICT_MARGIN_ROWS
);
this.pollCensus();
}, 300);
}
scrollToRow(row: number) {
const scrollEl = this.scrollEl.value;
if (!this.sheet.value || !scrollEl) return;
const targetPx =
(row * FlyweightLogic.Class.ROW_HEIGHT - FlyweightLogic.Class.VIEWPORT_HEIGHT / 2) /
this.scrollScale;
const clamped = Math.max(
0,
Math.min(targetPx, this.totalHeight - FlyweightLogic.Class.VIEWPORT_HEIGHT)
);
scrollEl.scrollTop = clamped;
this.scrollTop.value = clamped;
}
/** Measurement/verification harness (same idea as the reference grids). */
protected installHarness() {
(window as unknown as { __fw: unknown }).__fw = {
rows: () => (this.sheet.value ? this.sheet.value.rows : 0),
cols: FlyweightLogic.Class.COLS,
createModel: () => this.createModel(),
hasModel: () => this.hasModel,
creationMs: () => this.creationMs.value,
stats: () => (this.sheet.value ? this.sheet.value.stats() : null),
scrollToRow: (row: number) => this.scrollToRow(row),
editCell: (row: number, col: number, input: string) =>
this.sheet.value?.write(row, col, input),
cellText: (row: number, col: number) => {
const cellEl = document.querySelector(
`[data-grid-cell][data-row="${row}"][data-col="${col}"]`
);
return cellEl ? (cellEl.textContent || '').trim() : null;
},
cellValue: (row: number, col: number) => {
const value = this.sheet.value?.valueAt(row, col);
return value && typeof value === 'object' ? String(value) : (value ?? null);
},
startRow: () => this.startRow
};
}
}
export namespace FlyweightGridPage {
/* Identity */
export const $Class = Static($FlyweightGridPage); // anchor — it declares statics
export let Class = Reactive($Class);
export type Instance = typeof Class.Instance;
/* Types */
/** One rendered row: its index plus the flyweight cells leased to it. */
export interface PageRow {
row: number;
cells: FlyweightCell.Model[];
}
}vue
<script setup lang="ts">
/**
* Standalone demo: 20 columns × 1,000,000 rows (20,000,000 cells).
*
* The SFC is now a thin shell per the ivue operating manual: ONE raw
* `FlyweightGridPage` instance drives the template; only the template-ref
* target is destructured. All logic lives as named methods on the class.
*/
import './grid.css';
import { FlyweightLogic } from './FlyweightLogic';
const Logic = FlyweightLogic.Class;
import { FlyweightGridPage } from './FlyweightGridPage';
const page = new FlyweightGridPage.Class();
// THE STATE DESTRUCTURE — every Ref/Computed the template touches, grouped.
// Plain getters (hasModel, modelCells, totals, offsets…) and methods stay
// dotted on the instance.
const {
// state refs
creationMs,
census,
draft,
// computed refs
visibleRows,
// element refs
scrollEl
} = page;
</script>
<template>
<section class="fw-page">
<header>
<h1>Flyweight Grid — 20 × 1,000,000 <small>(20,000,000 cells)</small></h1>
<p class="fw-sub">
Columnar ground truth · flyweight cell facades · two-tier discovered dependency graph.
Google Sheets caps at 10M cells — this document cannot exist there. The census below is the
law, live:
<em>cost ∝ observed, never ∝ existing.</em>
</p>
</header>
<div class="fw-controls">
<button class="fw-btn" @click="page.createModel()">create model (20M cells)</button>
<template v-if="page.hasModel">
<span class="fw-stat"
><b>{{ page.modelCells.toLocaleString() }}</b> cells</span
>
<span class="fw-stat"
><b>{{ creationMs.toFixed(1) }}</b> ms create</span
>
<span class="fw-stat"
><b>{{ census.fineRefs.toLocaleString() }}</b> fine refs</span
>
<span class="fw-stat"
><b>{{ census.blockRefs.toLocaleString() }}</b> block refs</span
>
<span class="fw-stat"
><b>{{ census.formulaComputeds.toLocaleString() }}</b> formula computeds</span
>
</template>
</div>
<template v-if="page.hasModel">
<!-- Live totals over the FULL million rows (block tier: 245 edges each) -->
<div class="fw-totals">
<span v-for="entry in page.totals" :key="entry.label" class="fw-total">
<code>{{ entry.label }}</code> =
<b>{{ Logic.displayOf(entry.total.value) }}</b>
</span>
</div>
<div class="fx-bar">
<span class="fx-name">{{ page.activeRefLabel }}</span>
<span class="fx-val">{{ page.activeSourceLabel }}</span>
</div>
<div ref="scrollEl" class="gc-grid-scroll" @scroll="page.onScroll">
<div class="gc-inner">
<div class="gc-head">
<div class="gc-rownum gc-head-cell">#</div>
<div v-for="col in Logic.COLS" :key="col" class="gc-cell gc-head-cell">
{{ page.headerLabel(col) }}
</div>
</div>
<div class="gc-viewport" :style="page.viewportStyle">
<div class="gc-rows" :style="page.rowsStyle">
<div v-for="pageRow in visibleRows" :key="pageRow.row" class="gc-row">
<div class="gc-rownum">
{{ page.rowNumber(pageRow.row) }}
</div>
<div
v-for="cell in pageRow.cells"
:key="cell.col"
class="gc-cell"
:class="cell.cssClass"
data-grid-cell
:data-row="cell.row"
:data-col="cell.col"
:title="cell.source"
@click="page.edit(cell)"
>
<input
v-if="page.isEditing(cell.row, cell.col)"
class="gc-edit"
v-model="draft"
autofocus
@blur="page.onEditBlur()"
@keyup.enter="page.onEditEnter()"
/>
<template v-else>{{ cell.display }}</template>
</div>
</div>
</div>
</div>
</div>
</div>
</template>
<div v-else class="fw-empty">
No model yet — click <b>create model (20M cells)</b>. Creation fills ~95 MB of typed
arrays and allocates <b>zero</b> reactive state.
</div>
</section>
</template>ts
import { Static } from '../../Static';
/**
* Config, column layout and value mapping for the flyweight grid — a
* static capability class rather than a bag of exports, so a variant
* grid EXTENDS it (`class $WideGrid extends FlyweightLogic.$Class`
* overriding COLS or patternSource) instead of forking the file.
* Nothing here is reactive and nothing imports the parser — the same
* division of labor as the formula grid's `FormulaLogic`
* (reference, not imported).
*
* Layout — 20 columns × 1,000,000 rows = 20,000,000 cells, ~55% formulas
* (matching the formula grid's density story), expressed as per-column
* PATTERNS so formula sources cost 20 closures instead of 11M strings:
*
* A–D (0–3) numeric source data (deterministic, ~7.7% blanks)
* E (4) =A{r}+B{r} point arithmetic
* F (5) =C{r}-D{r} point arithmetic
* G (6) =SUM(A{r}:D{r}) small range → fine tier
* H (7) =IF(A{r}>0,B{r},C{r}) conditional dependency (marquee)
* I (8) =H{r}*2 formula-on-formula (point)
* J (9) =J{r-1}+A{r} running sum, block-reset every 50
* K…T (10–19) even = data, odd = =<left1>{r}+<left2>{r} (cross mesh)
*
* HOT PATH: Static()'s bound methods are plain-function speed once
* read — the only per-call cost is reading the method through the
* accessor inside a loop. FlyweightSheet's 9,000,000-call seeding loop
* therefore destructures the methods it needs once
* (`const { isDataCol, numDataValue } = this.Logic`) — one read of the
* sheet's overridable Logic seam, so BOTH swap axes are honored: a
* class swapped into the namespace slot, and a sheet subclass
* overriding `get Logic()` to route the whole layer elsewhere — and
* measures at or better than the original module functions (77-82ms vs
* 89ms for 20M cells, in-browser medians). Ordinary call counts can use
* `FlyweightLogic.Class.method()` directly and never notice.
*/
class $FlyweightLogic {
static readonly COLS = 20;
static readonly ROWS_1M = 1_000_000;
/** Rows per coarse invalidation block (2^12). 1M rows → 245 blocks/column. */
static readonly BLOCK_SHIFT = 12;
static readonly BLOCK_ROWS = 1 << 12; // 4096
/** Ranges up to this many cells subscribe per-cell (fine tier, precise);
* larger ranges subscribe per-block (coarse tier, O(blocks)). */
static readonly FINE_RANGE_LIMIT = 64;
/** Running-sum reset block — keeps dependency chains shallow (reference:
* the formula grid's RUNSUM_BLOCK rationale). */
static readonly RUNSUM_BLOCK = 50;
/** Row-windowing geometry for the demo UI. */
static readonly ROW_HEIGHT = 28;
static readonly VIEWPORT_HEIGHT = 448;
static readonly OVERSCAN = 4;
protected static readonly AGG_RE =
/^\s*(SUM|AVERAGE|MIN|MAX|COUNT)\(\s*([A-Z]+)(\d+)\s*:\s*([A-Z]+)(\d+)\s*\)\s*$/i;
/** Spreadsheet column label: 0→A, 25→Z, 26→AA … */
static colLabel(colIndex: number): string {
let label = '';
let remaining = colIndex + 1;
while (remaining > 0) {
const letterIndex = (remaining - 1) % 26;
label = String.fromCharCode(65 + letterIndex) + label;
remaining = Math.floor((remaining - 1) / 26);
}
return label;
}
/** Which columns hold numeric source data (the rest are formula patterns). */
static isDataCol(col: number): boolean {
if (col <= 3) return true;
return col >= 10 && col % 2 === 0;
}
/**
* Deterministic numeric seed for a data cell — NUMERIC (no string
* round-trip: 9M cells fill straight into Float64Arrays). ~7.7% blanks →
* null. Same (row,col) → same value on every build.
*/
static numDataValue(row: number, col: number): number | null {
const seed = row * this.COLS + col;
if (seed % 13 === 5) return null;
const value = ((seed * 2654435761) % 100000) / 100 - 500; // −500 … 500
return Math.round(value * 100) / 100;
}
/**
* The default formula SOURCE for a formula-column cell — generated on
* demand from the column pattern (row is 0-based; emitted refs are
* 1-based). Data columns return null (their ground truth lives in the
* typed arrays).
*/
static patternSource(row: number, col: number): string | null {
const rowNumber = row + 1;
switch (col) {
case 0:
case 1:
case 2:
case 3:
return null;
case 4:
return `=A${rowNumber}+B${rowNumber}`;
case 5:
return `=C${rowNumber}-D${rowNumber}`;
case 6:
return `=SUM(A${rowNumber}:D${rowNumber})`;
case 7:
return `=IF(A${rowNumber}>0,B${rowNumber},C${rowNumber})`;
case 8:
return `=H${rowNumber}*2`;
case 9:
return row % this.RUNSUM_BLOCK === 0
? `=A${rowNumber}`
: `=J${rowNumber - 1}+A${rowNumber}`;
default:
if (col % 2 === 0) return null;
return `=${this.colLabel(col - 1)}${rowNumber}+${this.colLabel(col - 2)}${rowNumber}`;
}
}
/** 1-based column index from a spreadsheet label: A→1, Z→26, AA→27 … */
static colIndexFromLabel(label: string): number {
let index = 0;
for (let position = 0; position < label.length; position++)
index = index * 26 + (label.charCodeAt(position) - 64);
return index;
}
/**
* Detect a formula body that is EXACTLY one aggregate over one contiguous
* range — the shape the columnar fast path can compute LINEARLY.
* Everything else returns null and takes the general parser. This matters
* because the stock parser's range aggregation is O(n²) in range size
* (measured: 27ms @ 10k cells → 40s @ 200k) — bulk aggregation belongs to
* the columnar layer.
*/
static matchSimpleAggregate(body: string): FlyweightLogic.SimpleAggregate | null {
const match = this.AGG_RE.exec(body);
if (!match) return null;
const aggregate = match[1].toUpperCase() as FlyweightLogic.SimpleAggregate['fn'];
const startCol = this.colIndexFromLabel(match[2].toUpperCase());
const startRow = parseInt(match[3], 10);
const endCol = this.colIndexFromLabel(match[4].toUpperCase());
const endRow = parseInt(match[5], 10);
if (startRow < 1 || startCol < 1 || endRow < startRow || endCol < startCol) return null;
return { fn: aggregate, startRow, startCol, endRow, endCol };
}
/** Does literal text start (after leading spaces) with '='? */
static isFormulaText(text: string): boolean {
const trimmed = text.trimStart();
return trimmed.length > 0 && trimmed[0] === '=';
}
/** Strip the leading '=' to get the formula body. */
static stripFormula(text: string): string {
return text.trimStart().slice(1);
}
/** Structural FormulaError detection (no parser import here). */
static isFormulaError(
value: FlyweightLogic.CellValue
): value is { _error?: string; error?: string } {
return typeof value === 'object' && value !== null && ('_error' in value || 'error' in value);
}
/** Resolve a NON-formula literal: '' → null, numeric → number, else text. */
static evalLiteral(text: string): FlyweightLogic.CellValue {
const trimmed = text.trim();
if (trimmed.length === 0) return null;
const numeric = Number(trimmed);
return !Number.isNaN(numeric) && Number.isFinite(numeric) ? numeric : text;
}
/** Display string for a resolved value. */
static displayOf(value: FlyweightLogic.CellValue): string {
if (value == null) return '·';
if (this.isFormulaError(value)) return String(value.error ?? value._error ?? '#ERR');
if (typeof value === 'number') {
return Number.isFinite(value)
? value.toLocaleString('en-US', { maximumFractionDigits: 2 })
: String(value);
}
if (typeof value === 'boolean') return value ? 'TRUE' : 'FALSE';
return String(value);
}
/** CSS class from error-ness, sign, and formula-ness. */
static cssOf(value: FlyweightLogic.CellValue, isFormula: boolean): string {
let base: string;
if (this.isFormulaError(value)) base = 'gc-err';
else if (value == null) base = 'gc-zero';
else if (typeof value === 'number')
base = value < 0 ? 'gc-neg' : value > 0 ? 'gc-pos' : 'gc-zero';
else base = 'gc-text';
return isFormula ? base + ' gc-formula' : base;
}
}
export namespace FlyweightLogic {
/* Identity */
export const $Class = Static($FlyweightLogic); // raw — children extend this
export let Class = $Class; // selected — callers read this
/* Types */
/** Cell kind tags in the columnar `kind` array. A plain enum, not a
* const enum: const enums cannot live in a namespace under
* isolatedModules (Vite), and the inlining they buy is noise here. */
export enum Kind {
Blank = 0,
Number = 1,
Text = 2,
Formula = 3
}
/** A value a cell can resolve to (FormulaError detected structurally). */
export type CellValue = number | string | boolean | null | { _error?: string; error?: string };
export interface SimpleAggregate {
fn: 'SUM' | 'AVERAGE' | 'MIN' | 'MAX' | 'COUNT';
/** 1-based bounds, parser convention. */
startRow: number;
startCol: number;
endRow: number;
endCol: number;
}
}The template is the whole wiring layer: one new FlyweightGridPage.Class(), the element-ref destructure, and markup that reads named members. Twenty million cells, and the SFC still owns no state — every derivation the rows need is a getter or a method on the page class.
Open in StackBlitz ⚡ — the playground boots with this example's route and file active.