cells

The cell data model, storage pattern, values, formulas, inline styles, and cell types.

Cell Storage

Cells are stored in a nested Y.Map structure within each sheet:

rows: Y.Map<Y.Map<Cell>>
       ^         ^
       |         └── Inner map: colId → Cell
       └── Outer map: rowId → inner map

This two-level nesting provides efficient row-level operations:

• Insert/delete row: Add or remove a single entry in the outer map
• Move row: Reorder in rowOrder array; the row’s cell data stays intact
• Access cell: Two map lookups: rows.get(rowId)?.get(colId)

// Read a cell
const rowMap = rows.get(rowId) as Y.Map<Cell> | undefined
const cell = rowMap?.get(colId) as Cell | undefined

// Write a cell
let rowMap = rows.get(rowId) as Y.Map<Cell>
if (!rowMap) {
    rowMap = new Y.Map()
    rows.set(rowId, rowMap)
}
rowMap.set(colId, cellData)

Cell Data Model

The Cell interface defines all possible fields on a cell. All fields are optional – an empty object {} represents a blank cell with all defaults.

Value Fields

Cell Type and Format

The ct object describes how the cell value should be interpreted and formatted:

interface CellType {
    t?: 't' | 'n' | 's' | 'b' | 'g'  // Type code
    fa?: string                         // Format code
    s?: Array<{ v: string }>           // Rich text segments
}

Type Codes (ct.t)

Format Codes (ct.fa)

The fa field contains a format pattern string compatible with spreadsheet number formatting:

Rich Text Segments (ct.s)

When a cell contains rich text (mixed formatting within a single cell), the ct.s array holds text segments:

{
    "ct": {
        "s": [
            { "v": "Bold text" },
            { "v": " and normal text" }
        ]
    }
}

Each segment contains a v field with the text content. Additional formatting fields may appear on individual segments.

Font Styling

All styling is inline on the cell – there is no named style or style inheritance system.

Alignment

Cell Appearance

Formula Storage

Formulas are stored as plain strings in the f field:

{
    "v": 150,
    "f": "=SUM(A1:A10)"
}

• The f field contains the formula string as entered by the user (always starts with =)
• The v field contains the last computed result
• Formula references use A1-style notation (e.g. A1, B2:D10, Sheet2!A1)
• The CRDT stores only the formula string – no ID-based cell references
• Formula evaluation is delegated to the FortuneSheet calculation engine at runtime

Default Stripping

To minimize CRDT storage overhead, fields that match their default values are stripped when saving a cell. The following fields are omitted when they match these defaults:

Fields with no default (like v, f, fc, bg, ht, vt) are stored whenever present.

Cell Addressing

Cells are addressed internally by their (rowId, colId) pair. For display, the column position in colOrder is converted to a letter code:

Row position in rowOrder is converted to a 1-based number. For example, the cell at position (row index 2, col index 0) displays as A3.