Dylan M. Taylor
bdf8b8cc75
* Use chrono for UTC/calendar conversion instead of hand-rolled copies Replaces the hand-rolled civil_from_days / days_from_civil copies and the is_leap / days_in_month calendar helpers with chrono as a workspace dependency (default-features = false, std only, so wasm is unaffected). The spreadsheet serial-date semantics are untouched: Excel's 1900 fictitious leap day (serial 60 = 1900-02-29), the 1899-12-30 / 1904-01-01 serial offsets, Excel's weekday numbering and the 1900/1904 systems keep their explicit special cases in serial_from_ymd / datetime_from_serial / days_in_month_in. chrono only backs the plain proleptic-Gregorian day-number <-> date conversion and the leap-year / month-length helpers those build on; a small fallback keeps the old answer for dates outside chrono's NaiveDate range. The duplicate local is_leap in the financial functions now uses the core one. Output is byte-identical and pinned by the existing date, parse, financial and logging tests. AGENTS.md now says time goes through chrono. Follow-up to storytold/cadcraft#1785 * Never panic on out-of-range clocks or years; keep calendar results outside chrono's range - logging::timestamp: chrono's From<SystemTime> unwraps, so a clock past year 262143 panicked inside the logger. Use the fallible DateTime::from_timestamp and read such a clock as the epoch, like the old saturating code. Years past 9999 are written with {:04} (not %Y, which prefixes a '+'). - date::is_leap: restore the Gregorian leap-year rule for years outside chrono's NaiveDate range (e.g. is_leap(400000) is true again) via direct arithmetic. - date::days_in_month: compute the December boundary with checked_add so days_in_month(i32::MAX, 12) no longer overflows, and compute month lengths through days_from_civil's fallback so out-of-range years keep their real lengths (e.g. days_in_month(400000, 2) is 29). Invalid months still return 0. - civil_from_days: add missing docstring. - AGENTS.md: note the narrow out-of-range fallback exception to the chrono rule. * Don't build an unrepresentable SystemTime in the far-future test UNIX_EPOCH + Duration::from_secs(u64::MAX / 2) overflows Windows' SystemTime and panicked before timestamp() ran, failing the Windows test job. Build it with checked_add and only assert where it exists. * Route out-of-range dates through chrono's 400-year cycle, not hand-rolled copies The PR kept hand-rolled Hinnant `days_from_civil_fallback`/`civil_from_days_fallback` copies for dates outside chrono's ±262143-year range, plus a hand-rolled Gregorian leap rule in `is_leap` and an i32::MAX special-case in `days_in_month`. AGENTS.md carved a "narrow fallback" exception for them, which left calendar arithmetic outside chrono after all. Replace all of it with the Gregorian 400-year cycle (146_097 days): chrono converts the day/year within one cycle and whole cycles are added back via i128 (so the i32/i64 extremes can't overflow). `is_leap` and `days_in_month` reduce the year with `rem_euclid(400)` (leap years and month lengths repeat every 400 years), which also removes the December `i32::MAX` overflow special-case. chrono is now the only calendar logic, and every output is unchanged: verified the cycle result equals the old formula over wide ranges and at the i32/i64 extremes with a scratch chrono program. The Excel 1900 leap bug (serial 60 = fictitious 1900-02-29) and 1904 semantics are untouched -- `serial_from_ymd`/ `datetime_from_serial` only ever hand the converters in-range years, so their serials are byte-for-byte the pre-chrono ones (pinned by a new test). New tests pin `days_from_civil`/`civil_from_days` past chrono's range on both sides of the epoch, round-tripping, with values from the old formula; the existing leap/month-length-beyond-range test still passes unchanged. Removed the AGENTS.md "narrow fallback" exception. Tested: cargo test -p gridcraft-core -p gridcraft-functions; fmt --check; clippy --all-targets -D warnings. * time: preserve out-of-range years in the log timestamp instead of the epoch `DateTime::from_timestamp(..).unwrap_or_default()` changed the existing output: a clock set far ahead (an input the old hand-rolled civil-from-days converted) collapsed to `1970-01-01`. Restore the old conversion domain with a cycle-based helper: reduce by whole 400-year Gregorian cycles (146_097 days), convert the in-range remainder with chrono, and carry the year back as i128. Only the year leaves chrono's range; month/day/time stay exact. Pre-1970 still clamps to the epoch as before. chrono stays the only calendar logic (no new features). apps/gridcraft logging.rs `timestamp` (SystemTime, u64 secs), pinned via a platform-safe `UNIX_EPOCH.checked_add`: u64::MAX/2 s → "292277026596-12-04T15:30:07.000Z" (was "1970-01-01..."), 10e12 s → "318857-05-20T17:46:40.000Z", 253_402_300_800 s → "10000-01-01...". * Name the 400-year range extension as the one exception to the time rule The rule said never to hand-roll calendar math, but the range fix (shifting by whole 400-year Gregorian cycles so dates past chrono's year range keep their old output) is cycle arithmetic, so the rule and the code disagreed. The rule now names that exception: the library still computes month, day and time, and only whole cycles are carried in the year. * Say the library computes month and day; time-of-day is plain arithmetic Narrows the range-extension wording: the date library computes the calendar fields, and splitting seconds into hours, minutes and seconds is ordinary arithmetic, which is what the code does.
GridCraft
Spreadsheets and data; an open-source, high-performance modern spreadsheet application, built in pure Rust.
A fast, open-source, clean-room take on modern spreadsheet workflows. It runs natively on macOS,
Windows, Linux and BSD, and in the browser via WebAssembly.
By the ArtCraft team.
GridCraft on getartcraft.com · ArtCraft · All Crafting Apps
Quarterly Sales Dashboard: a table with a totals row, conditional formatting, sparklines and two live charts — built entirely from GridCraft commands (File → New → Sample).
Note
ArtCraft is a community of artists from all walks of life. Painters, photographers, filmmakers, illustrators, designers, animators, hobbyists, and people who picked up a pencil last week. If you make things, you're one of us. Come say hi on Discord.
A look around · Why GridCraft · Quick start · For agents · Architecture · Roadmap · The Crafting Apps · License and credits
A look around
 Formatting. Accounting formats, cell styles, conditional rules and colour scales, frozen headers and a bar chart. |
 Formulas. 500+ functions, dynamic arrays, LET and LAMBDA, structured table references. |
 Dark mode and the Insert tab: tables, charts, sparklines, pictures, shapes, links and comments. |
 Pivot tables. Field list, filters, layouts, date grouping and show-values-as, saved to and read from XLSX. |
 Charts. Seventeen chart types, Chart Design tab and a Format pane; selecting a chart outlines its source data. |
 Page Break Preview, print settings, and PDF export and printing. |
Why GridCraft
- Familiar. Ribbon, formula bar, Name Box, sheet tabs, keyboard shortcuts, fill handle, point-mode formula entry with coloured references, Format Cells, Paste Special, conditional formatting, tables, charts and more. Everything is right where you expect it.
- Compatible. XLSX is the native format: styles, themes, formulas (including dynamic arrays),
tables, conditional formats, validation, comments, hyperlinks, charts, pictures, sparklines,
pivot tables and print settings round-trip. CSV and TSV too.
Legacy 97-2003
.xlsworkbooks open with their values, formulas and number formats (formatting and objects not yet). XLSB worksheet data can be imported, using saved values instead of formulas. ODS worksheet data can be imported, using saved values instead of formulas. Static pictures can live inside cells, fitting their size and moving with the data. - Capable. A dependency-graph calculation engine with dynamic arrays and spilling, 500+ worksheet functions plus LET, LAMBDA, MAP, REDUCE, SCAN, BYROW, BYCOL and MAKEARRAY, structured table references, a comprehensive number-format language, sort and AutoFilter, Flash Fill, data validation, outlining and subtotals.
- Fast. Copy-on-write workbooks (undo snapshots are nearly free), incremental recalculation, and a virtualised grid that only lays out what's on screen.
- Agent-native. Every ribbon button, menu item, dialog, keystroke and mouse gesture is a command that agents can run over a JSON control channel, an MCP server, or the CLI.
- Everywhere. One Rust codebase for desktop and the web. No subscription, no licence server, no telemetry.
Quick start
cargo run --release -p gridcraft # desktop app
cargo run --release -p gridcraft -- --sample sales # open a sample (sales, budget, grades)
cargo run --release -p gridcraft -- book.xlsx # open a workbook
cargo run --release -p gridcraft -- --sample sales --control 7979 # + JSON control channel
cargo xtask ci # fmt, clippy, tests, assets, layering, wasm
Choose Español under View → Interface language for Spanish formula names, decimal commas, and semicolon arguments. Workbooks, clipboard exchange, and programmatic APIs retain canonical English syntax.
Web
cd apps/gridcraft-web && trunk build --release # → dist/web (serve it with any static server)
cd apps/gridcraft-web && trunk serve --release # http://127.0.0.1:8771 (?sample=sales opens a sample)
You need trunk and the wasm32-unknown-unknown target. Open uses the
browser's file picker (dropping files works too) and Save downloads the workbook.
Ribbon access keys
Press and release left Alt on Windows/Linux/BSD, or press F10 on any platform, then type a sequence below one key at a time. Keytips appear on the supported Home controls and menu items. On macOS, use F10 (Fn+F10 if required by your keyboard); Option remains available for entering accented characters.
| Sequence after Alt/F10 | Action |
|---|---|
H A L / H A C / H A R |
Align left / center / right |
H V S or legacy E S |
Open Paste Special |
H O I or legacy O C A |
AutoFit selected columns |
In Paste Special, T/V/F/C select formats/values/formulas/comments, and E toggles Transpose. Enter applies the selected options; Escape cancels the dialog. These letters also work with Alt held on Windows/Linux/BSD.
Escape backs out one keytip level; Alt/F10 again exits keytips. Clicking, scrolling, or switching windows cancels navigation. Access keys do not start while editing text or using another dialog. This is initial support for these Home and legacy paths; other ribbon commands and full mouse-free navigation remain to be implemented. Browsers or desktop environments may reserve Alt/F10 for their own menus.
Logs
The desktop app writes its log to standard error and to gridcraft.log in the logs folder
next to its settings: ~/.config/gridcraft/logs on Linux and BSD ($XDG_CONFIG_HOME/gridcraft/logs
when set), ~/Library/Application Support/GridCraft/logs on macOS and
%APPDATA%\GridCraft\logs on Windows. Each start moves the previous log to gridcraft.1.log and
that one to gridcraft.2.log, so the log of a run that crashed survives the next start; attach
them to a bug report. A log file stops growing at 16 MiB. By default GridCraft's own crates log
at info and everything else at warn; RUST_LOG replaces that with env_logger-style
directives, e.g. RUST_LOG=debug or RUST_LOG=warn,gridcraft_engine=debug (a trailing *
matches a prefix: gridcraft*=debug). Runs with GRIDCRAFT_NO_PREFS set (no saved settings)
log to standard error only.
For agents: MCP, CLI and the control channel
claude mcp add gridcraft -- gridcraft-cli mcp # headless MCP server
gridcraft-cli mcp --connect 7979 # MCP bridged to a running window
gridcraft-cli eval '=XLOOKUP("b",{"a","b"},{1,2})' # → 2
gridcraft-cli run --sample budget --cmd 'home.bold={"range":"B4:F4"}' --out budget.xlsx
gridcraft-cli cat budget.xlsx --range B4:F15 # aligned text table
gridcraft-cli commands --search chart # every command and its params
The MCP server offers tools such as read_range, write_range, set_cell, evaluate_formula,
format_range, insert_chart, create_table, sort_range, filter and execute_command
(which reaches every one of GridCraft's commands). The desktop app's control channel adds real
pointer and keyboard input, dialogs and screenshots. See docs/mcp.md,
docs/cli.md and docs/control-protocol.md.
Architecture
GridCraft is an engine-first Cargo workspace with enforced layering (cargo xtask layers). The
egui frontend is a separate crate, so the UI can be swapped without touching the engine.
| Layer | Crates |
|---|---|
| L0 | core (addresses, values, errors, dates, input parsing) · numfmt (number format codes) |
| L1 | formula (lexer, parser, printer, reference adjustment) · functions (worksheet function library) |
| L2 | model (workbook, sheets, copy-on-write cells, styles, tables, charts…) · calc (dependency graph, evaluator, dynamic arrays) · xlsx (XLSX, CSV, plus XLSB and ODS data import) |
| L3 | chart (toolkit-free chart layout and rendering) |
| L5 | engine (session, commands, history, clipboard, fill, sort, filter, file I/O) |
| L6 | ui-egui (spreadsheet UI, control channel) · mcp (MCP server) |
| L7 | apps/gridcraft, apps/gridcraft-cli, apps/gridcraft-web |
- Contributor and agent rules (clean-room, asset policy, never-crash, quality gates):
AGENTS.md - Bundled assets: each one is listed with its licence in
ATTRIBUTION.md - Releases: signed macOS, Windows, Linux, BSD and web builds; see
docs/releasing.md
Roadmap
GridCraft is in alpha: the core workflow works end to end, but depth, fidelity and file
compatibility are still rough. It covers 89% of standard ribbon commands in our catalog
(docs/parity-checklist.md) and 513 standard worksheet functions
(docs/function-parity.md); this is a parity inventory, not a count of working implementations. Weighted by what spreadsheet users rely on, we
estimate it is about 50% ready for real work. Next up: XLSX fidelity on real-world files, very large
workbooks and multi-threaded recalc, chart depth, text in every script, and .xls import. Stage,
numbers and estimates are in ROADMAP.md; the ranked work list is docs/gaps.md.
Downloads
Download GridCraft from GitHub: the latest release has every build listed below, and all releases has earlier versions and their notes. <ver> in the file names is the version number, and SHA256SUMS.txt lists a checksum for every file.
Windows
| Build | Installer | Portable |
|---|---|---|
| x64 (64-bit Intel/AMD) | gridcraft-<ver>-windows-x64.msi |
gridcraft-<ver>-windows-x64-portable.zip |
| arm64 (Snapdragon and other ARM PCs) | gridcraft-<ver>-windows-arm64.msi |
gridcraft-<ver>-windows-arm64-portable.zip |
| x86 (32-bit) | gridcraft-<ver>-windows-x86.msi |
gridcraft-<ver>-windows-x86-portable.zip |
Installers and executables are code-signed. The MSI installer offers an optional desktop shortcut (unchecked on a new installation).
If the app doesn't open on Windows: the desktop app initializes only DirectX 12 by default.
Letting wgpu also create an OpenGL instance can crash some graphics drivers (AMD's
atio6axx.dll) before the window appears, so the app would flash in Task Manager and quit.
WGPU_BACKEND overrides the default for troubleshooting (for example dx12 or vulkan). In
PowerShell, from the folder containing the executable:
$env:WGPU_BACKEND = "vulkan"
& .\gridcraft.exe
Remove-Item Env:WGPU_BACKEND # restore the default for later launches
An explicit gl override can bring the driver crash back on affected systems, and vulkan can
bring back a crash in some Intel UHD Graphics drivers (igvk64.dll, #120). The macOS, Linux and
web backend defaults are unchanged.
If the app is slow on an older Windows PC, or DirectX 12 can't start: when DirectX 12 finds no
graphics card with a driver for it, it only offers the Windows-provided software renderer, which draws every
frame on the processor. In that case GridCraft uses OpenGL instead, without setting anything; if
the first renderer fails to start, it tries the other one once. The log file records the choice
(lines starting with graphics:). WGPU_BACKEND still overrides it (and then nothing else is
tried), e.g. $env:WGPU_BACKEND = "gl" or "dx12".
DirectX 12 shaders are compiled with FXC, which is part of Windows, so no dxcompiler.dll or
dxil.dll is needed, and a copy another program put on PATH can no longer stop the app at start
("Parent device is lost", #339). $env:WGPU_DX12_COMPILER = "dxc" (or "auto") selects wgpu's DXC
handling again for troubleshooting.
macOS
| Build | File | Notes |
|---|---|---|
| App, universal (Apple silicon + Intel) | gridcraft-<ver>-macos-universal.dmg |
Signed and notarized |
| Command-line tool, universal | gridcraft-cli-<ver>-macos-universal.zip |
Signed and notarized |
Linux
| Format | x86_64 | aarch64 (ARM64) | Notes |
|---|---|---|---|
| AppImage | gridcraft-<ver>-linux-x86_64.AppImage |
gridcraft-<ver>-linux-aarch64.AppImage |
Runs anywhere; updates itself with AppImageUpdate (.zsync files) |
| Flatpak | gridcraft-<ver>-linux-x86_64.flatpak |
gridcraft-<ver>-linux-aarch64.flatpak |
Sandboxed; flatpak install --user <file> |
| Debian/Ubuntu | gridcraft-<ver>-linux-x86_64.deb |
gridcraft-<ver>-linux-aarch64.deb |
|
| Fedora/RHEL/openSUSE | gridcraft-<ver>-linux-x86_64.rpm |
gridcraft-<ver>-linux-aarch64.rpm |
|
| Tarball | gridcraft-<ver>-linux-x86_64.tar.gz |
gridcraft-<ver>-linux-aarch64.tar.gz |
Unpack anywhere |
FreeBSD
| Build | File |
|---|---|
| x86_64 | gridcraft-<ver>-freebsd-x86_64.tar.gz |
Web (WebAssembly)
| Build | File | Notes |
|---|---|---|
| Static site | gridcraft-web-<ver>.zip |
Runs in a modern browser; host it on any static server |
The Crafting Apps
GridCraft is one of the Crafting Apps: free, open-source creative tools from the ArtCraft team, each written from scratch in Rust and each able to stand on its own.
| App | What it's for | Code | Learn more | |
|---|---|---|---|---|
 |
PhotoCraft | Image editing: layers, masks, type and real PSD files | GitHub | Website |
 |
VectorCraft | Vector illustration | GitHub | Website |
 |
FilmCraft | Video editing, color and sound | GitHub | Website |
 |
LightCraft | Photo library and raw development | GitHub | Website |
 |
PdfCraft | Reading, organizing and protecting PDFs | GitHub | Website |
 |
EffectCraft | Motion graphics and visual effects | GitHub | Website |
 |
DesignCraft | Page layout and publishing | GitHub | Website |
 |
GridCraft | Spreadsheets and data · you are here | GitHub | Website |
And ArtCraft itself, our AI image and video studio for artists who want real control.
Come make things with us
Our Discord is where artists of every kind hang out: people who paint, shoot, draw, cut film, set type, and people still figuring out what they like to make. Share what you're working on, ask for help, tell us what's broken, or tell us what you wish these tools could do. Whatever your medium and however long you've been at it, you're welcome here.
discord.gg/artcraft · getartcraft.com · The Crafting Apps · GridCraft
License and credits
GridCraft is dual-licensed under MIT or Apache-2.0, at your option. Copyright (c) 2026 ArtCraft Team and the GridCraft contributors. Required notices are in NOTICE.
Bundled fonts, icons, images and other assets keep their own open licenses; each one is listed with its author, source and license in ATTRIBUTION.md.
All UI icons are drawn in code and are original; the sample workbooks and every screenshot in this README were made with GridCraft itself. GridCraft bundles no fonts: it uses the fonts installed on your system.
The ArtCraft name, wordmark and logos in docs/brand/ are trademarks of the
ArtCraft Team and are not covered by this license. They may be used only unmodified, and only as
part of this repository and GridCraft, under docs/brand/LICENSE-brand.txt.
Forks and modified versions must remove them.
Made by the ArtCraft team and community.