fix(preview): index rows and cells by their present keys, cap theme size

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ExcelJS keeps a row's cells at `_cells[col - 1]`, so a row whose only
cell sits in XFD is a dictionary-mode array that `eachCell` and
`hasValues` (behind `eachRow`) walk to index 16,384. The worker walked
each row four times at load and once per tile, so a small file of
far-column rows took seconds to load and to tile.

`worksheetMetadata` now builds each sheet's row and cell index from
`Object.keys(sheet._rows)` and `Object.keys(row._cells)`, sorted
numerically, skipping falsy and Null-type cells exactly as
`eachCell({ includeEmpty: false })` does and keeping a row only when it
holds one such cell (`hasValues`). Styles, extent and row heights come
from that one pass and merges from `sheet._merges`; `sendTile` reads
each row's cells from the index.

`parseThemePalette` returns the default palette for a theme above
64 * 1024 characters, since its patterns are quadratic on unclosed tags.

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This commit is contained in:

Aamer Akhter

2026-10-03 17:21:41 -04:00

parent c1811fd716

commit 7d3e27fb6d

7 changed files with 193 additions and 23 deletions

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docs/architecture-invariants.md

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