vectorcraft/docs/development.md

Development

Web build

apps/vectorcraft-web runs the same VectorcraftApp in the browser through eframe's web runner. The renderer is wgpu: WebGPU where the browser has it, WebGL2 otherwise. It is Rust only; the only JavaScript is the glue wasm-bindgen generates.

brew install trunk                 # or: cargo install trunk --locked
rustup target add wasm32-unknown-unknown
cd apps/vectorcraft-web
trunk build --release              # writes ../../dist/web (index.html, .js glue, .wasm)
trunk serve --release              # dev server on http://127.0.0.1:8766

What the web build needs: trunk, the wasm32-unknown-unknown target and cargo, nothing else (no POSIX shell, so it works the same on Windows). Optionally, CRAFT_FONTS_DIR set to an absolute craft-fonts checkout adds the fonts the site serves beside the wasm: Trunk's post_build hook runs cargo xtask web-fonts, which copies them into dist/web/fonts/ (it does nothing without CRAFT_FONTS_DIR, and skips with a warning any listed face an older checkout lacks). See Arabic fonts and the web build.

Any static file server works for dist/web, for example python3 -m http.server 8766 inside that directory. The release .wasm is about 17.5 MB, or 7.1 MB gzipped, so serve it with compression.

URL flag: ?webgl forces the WebGL2 backend.

How the web shell (apps/vectorcraft-web/src/web.rs) differs from desktop:

• Open sets Services::open_async, which shows rfd::AsyncFileDialog. The bytes arrive in Services::inbox, which the app drains every frame.

• Save / Save As / Export go through Services::download: a Blob, an object URL and a temporary <a download>, all created from Rust. There is no save dialog, so the suggested name becomes the download name.

• Drag-and-drop: WebShell takes the frame's dropped_files before the app sees them, reads each with DroppedFile::bytes_async and pushes the bytes into the inbox (files to be placed on a canvas go to Services::place_inbox with their place::DropAt: the document they were dropped on, by uid, and the point; VectorcraftApp::drop_target decides from the position the page's drag events give). Desktop drags carry no position (winit 0.30 reports none, and the pointer position egui last had is stale), so the desktop app decides by kind: documents open, pictures and text are placed in the middle of the view. On the web and the desktop, swatch and graphic style libraries, Libraries panel files, presets and plug-ins open wherever they are dropped, as File › Open opens them (io::opens_as). A file that arrives after another document became active still lands in its own document, which becomes active again; if that document closed meanwhile, the file is not placed and the status bar says so. (The app's synchronous drop path is compiled out on wasm32.)

• Data Recovery keeps its copies in localStorage (vectorcraft-recovery/<area>/<name>, shared by the site's tabs), so tabs can't lock their areas the way desktop apps lock a folder (RecoveryStore::lock). Each tab holds its area with a heartbeat it refreshes every minute and, where the browser has Web Locks (secure pages: https:// or localhost), with a Web Lock named after the area (apps/vectorcraft-web/src/locks.rs, through js_sys::Reflect since web-sys has them only as an unstable API). The browser releases the lock only when the tab is gone, not while its timers are paused in the background, which a heartbeat can't tell apart (#367). navigator.locks.query() is asynchronous, so the shell keeps a snapshot refreshed every 10 seconds (taken once before the first frame); a snapshot older than a minute counts every area as held. An area is offered as a crash's leftovers only when no tab holds its lock and its heartbeat is older than three intervals. Without Web Locks a paused tab can still be taken for gone; it repairs that when it resumes: its next heartbeat (or recovery save) writes again the copies missing from its area, and a heartbeat newer than the one the other tab wrote taking the area over makes the area running again for that tab.

• Losing the graphics (#369): the browser can drop the page's WebGPU device or WebGL context (a GPU reset, a driver update, too many tabs on the GPU; or a script calling device.destroy() / WEBGL_lose_context.loseContext()). The app goes on without it, so the shell watches for it: wgpu's device-lost callback for WebGPU, the canvas's webglcontextlost event for WebGL2. Both report to a graphics::GraphicsLoss, and the next frame of WebShell::logic handles it:

  1. VectorcraftApp::graphics_lost writes Data Recovery copies of the modified documents at once (to browser storage, also when Data Recovery is turned off).
  2. The shell puts a fresh <canvas> in place of the dead one (a canvas whose WebGL context is lost can't get another) and starts the same WebRunner again on it, with new graphics and a new egui context, handing over the same VectorcraftApp: documents, undo history, selection and panels stay as they were. Its Services are made again for the new context, and the status bar says the graphics were restarted.
  3. Textures belong to the egui context they were uploaded to. The app notices the new context (VectorcraftApp::adopt_context) and uploads everything again: fonts and theme, the canvas, the place cursor's thumbnails, and every per-thread texture cache (thumbnails, previews, font samples), which are graphics::TexCaches for that reason. A new texture cache must be a TexCache (or live in the context's ctx.data), or it shows stale or wrong pictures after a restart.
  4. If no new graphics can be had (no adapter, WebGL blocked after repeated losses) or the graphics were lost more than three times, the shell gives up: the dead canvas is removed, the app lets go of its recovery area but not its copies (recovery::leave: its heartbeat and Web Lock go, so the reloaded page offers the copies at once). The Web Locks are started once, before the first frame, and kept across graphics restarts, so a restarted tab stays the owner of its area and the page says to reload.

  To try it, in the browser console: for WebGL2 (?webgl), document.querySelector('canvas').getContext('webgl2').getExtension('WEBGL_lose_context').loseContext(). For WebGPU, keep the device the page creates (wrap GPUAdapter.prototype.requestDevice before the page loads) and call its destroy().

  The desktop app can't make a new device for its window (eframe can't), so on a lost device (a driver reset) it logs the reason, writes the recovery copies, and says in the status bar to save and restart. Once the copies are written, closing the window skips the Save Changes question, which it can't show: the next launch offers the changes back.

• No control server: browsers can't listen on TCP. To automate the web build, drive headless Chrome with --remote-debugging-port.

• Quick smoke test: "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome" --headless=new --enable-unsafe-webgpu --screenshot=web.png --window-size=1440,900 --virtual-time-budget=15000 http://127.0.0.1:8766/ (headless Chrome on macOS gets a real WebGPU adapter).

Desktop graphics processor

The canvas is rasterized on the CPU (vectorcraft-render, vello_cpu); the GPU (wgpu, through eframe) only composites the canvas texture and draws the UI, so any GPU that can show the window will do. The desktop app picks the window's adapter itself (apps/vectorcraft/src/gpu.rs, eframe's native_adapter_selector) and logs every adapter it found and the one it uses.

• Order: adapters that report they can't present to the window are never tried; then the one WGPU_ADAPTER_NAME names; hardware before software (llvmpipe, WARP); the native backends (Vulkan, Metal, DX12) before OpenGL; with Automatic, the GPU the Wayland compositor draws with, then the GPU that drives a display, and among those the one that drives the primary display; then the power preference; then a GPU's DX12 adapter before its Vulkan one (Intel's Vulkan driver made the whole window flicker black, #545), keeping the system's order among equals.
• Windows backends: Direct3D 12, falling back to OpenGL. Vulkan isn't started at all unless WGPU_BACKEND asks for it (WGPU_BACKEND=vulkan): creating a Vulkan instance loads every installed Vulkan driver into the process, and a faulty one (Intel's igvk64.dll, #806) crashed the app before its window appeared.
• The GPU that drives the display. A GPU without a monitor is the wrong one even when it says it can show the window: on a desktop with a Ryzen's integrated GPU (no monitor) and an NVIDIA card driving both monitors, power saving picked the integrated GPU, Windows had to present every frame across adapters, and the integrated GPU's driver reset under that: the graphics device was lost, or the desktop's compositor went down and every monitor stayed black for minutes (pdfcraft#378). So Automatic asks the system which GPU drives which display and puts that GPU first; the power preference only orders the rest, and decides alone where the system can't say.
  • Windows: EnumDisplayDevices (the display devices attached to the desktop, and the primary one), through the winsafe crate; the PCI ids in each device id are matched against wgpu's adapters. The registry doesn't tell a user which adapter drives a display, and WMI reports a resolution for a GPU without a monitor, so neither is used.
  • Linux: the connected connectors in /sys/class/drm and their cards' PCI ids; a built-in panel (eDP, LVDS, DSI) counts as the primary display.
  • macOS, OpenGL adapters (no device id) and Metal (no ids at all): no match, so the power preference decides as before.
  • The log's first lines list the display GPUs (display GPUs (PCI vendor:device): 10de:2204 (primary)), every adapter with whether it drives a display, and the one drawn on and why (drawing on NVIDIA GeForce RTX 3090 (Dx12, DiscreteGpu): it drives the primary display). That is the first thing to look for in a black-window report.
• Preferences › Performance › Graphics Processor (gpuPreference): automatic (the default), lowPower (Power Saving, the integrated GPU) or highPerformance (the discrete GPU). The adapter is chosen when the window opens, so a change applies after a restart. Power Saving and High Performance are the user's own choice and order by kind alone, without looking at the displays; so does WGPU_POWER_PREF.
  • Automatic on Windows and macOS is the GPU that drives the primary display, then power saving: the system shows frames from any GPU, and presenting frames rendered on a discrete GPU through the integrated one made the window flicker on some hybrid laptops (#306). On a hybrid laptop the integrated GPU drives the panel, so both rules agree.
  • Automatic under Wayland puts the GPU the compositor draws with first: the compositor names it (the main_device of its linux-dmabuf feedback, protocol version 4; apps/vectorcraft/src/compositor_gpu.rs), and the log says the compositor draws with 10de:25ac. Which GPU drives a display only stands in for that, and can be wrong: on a hybrid laptop whose Hyprland ran on the NVIDIA GPU (AQ_DRM_DEVICES), the panel rule picked the Intel GPU behind the built-in panel, and the compositor showed nothing it drew, with no error, so neither the restart nor the first-frame watch below noticed. A compositor that doesn't say (linux-dmabuf older than version 4), or names a GPU no adapter matches, leaves the rules below in charge.
  • Automatic on Linux and the BSDs is the GPU that drives the panel or a monitor, then the system's order: Mesa's Vulkan device-select layer puts the GPU the desktop runs on first (the integrated one on hybrid laptops; DRI_PRIME and MESA_VK_DEVICE_SELECT steer it). A Wayland compositor may not accept frames from another GPU: on a desktop whose compositor ran on an NVIDIA GPU, rendering on the Ryzen's integrated GPU made KWin end the window's connection ("importing the supplied dmabufs failed") and 0.5.0 crashed at startup (#502).
  • 0.5.0 saved powerSaving, its default, for everyone; it reads as automatic.
• If the window fails on its adapter while starting up (an error from wgpu, or a panic inside wgpu or egui-wgpu during the first frames), the app starts again without that adapter and tries the next one, telling which in the status bar; the run that failed keeps its log as vectorcraft.1.log. On Unix the new app replaces the process (an AppImage stays mounted); on Windows it starts beside it. Adapters are told apart by backend and PCI ids, or by name where the backend reports no ids (Metal lists every GPU of a dual-GPU Mac as 0000:0000, #651). The adapters left out travel in VECTORCRAFT_GPU_SKIP (backend:vendor:device, such as Vulkan:1002:164e), one more on each restart, so the restarts end. When no adapter is left, the app logs why and exits with an error instead of panicking.
• If the window's first frame never reaches the screen within 20 seconds of the app being created (the files named at the start opened), the adapter counts as hanging and the app starts again without it in the same way (#964: High Performance on a hybrid laptop left the app running in the background with no window and nothing in the log). A window minimized at the start isn't counted. When the processor that hung was chosen in Preferences, the status bar points to Automatic.
• To recover from a Graphics Processor choice that doesn't work without editing files: start once with WGPU_POWER_PREF=low (or WGPU_ADAPTER_NAME=…), which overrides the preference for that start while settings still save, and set Graphics Processor back to Automatic. VECTORCRAFT_NO_PREFS=1 also starts without it, but saves nothing.
• Environment variables for when the choice still goes wrong, all read at startup and stronger than the preference:
  • WGPU_POWER_PREF: low, high or none (the system's order).
  • WGPU_ADAPTER_NAME: part of an adapter's name, any case (WGPU_ADAPTER_NAME=nvidia, =radv, =intel); the names are in the log.
  • WGPU_BACKEND: the backends to use, such as vulkan, dx12, metal or gl.
  • WGPU_VALIDATION_INDIRECT_CALL=1: turns wgpu's check of indirect draw arguments back on. VectorCraft draws nothing indirectly and turns it off, since the compute shader it needs fails to compile on some drivers (#651).
  • On Linux with Mesa, MESA_VK_DEVICE_SELECT=10de:2f04! (vendor:device as vulkaninfo --summary or lspci -nn show it) leaves only that GPU to Vulkan, and DRI_PRIME=1 picks the other GPU.
• Help › About and the control channel's ui.inspect (graphicsAdapter) show the adapter in use, and the app logs it at startup.

Logs

The desktop app writes its log records to standard error and to logs/vectorcraft.log next to the preferences (Linux $XDG_CONFIG_HOME/vectorcraft/logs/, by default ~/.config/vectorcraft/logs/; macOS ~/Library/Application Support/VectorCraft/logs/; Windows %APPDATA%\VectorCraft\logs\). A start launched from a desktop menu or the Dock has no terminal, so this file is what to attach to a bug report: the graphics adapter in use, a lost graphics device, panics the engine's guard recovered from and clipboard formats that couldn't be made land there. Each launch moves the previous log to vectorcraft.1.log (and that one to vectorcraft.2.log), so the log of a run that crashed survives the next start. The file stops growing at 16 MiB. --version writes no file, and runs with VECTORCRAFT_NO_PREFS log to standard error only.

By default VectorCraft's own crates log at info and everything else at warn. RUST_LOG replaces that with env_logger-style directives, for example RUST_LOG=debug, RUST_LOG=warn,vectorcraft_render=trace or RUST_LOG=info,wgpu_core=warn; a directive ending in * covers every target starting with it (vectorcraft*=debug). The logger is apps/vectorcraft/src/logging.rs. vectorcraft-cli mcp has its own logger, which sends records to the MCP client (docs/mcp.md).

Environment variables (desktop app)

Variable	Effect
VECTORCRAFT_CONTROL_PORT	Same as --control <port>, which overrides it; a value that isn't a port from 1 to 65535 stops the app
VECTORCRAFT_IN_WINDOW_MENUS	Any value but empty or 0: same as --in-window-menus (see macOS: the menu bar)
VECTORCRAFT_NO_PREFS	No preferences read or written, no default Data Recovery folder and no log file (agents' test runs)
WGPU_POWER_PREF	Graphics adapter: low, high or none (see Desktop graphics processor)
WGPU_ADAPTER_NAME	Graphics adapter by (part of) its name, any case (see Desktop graphics processor)
WGPU_BACKEND	Graphics backends: vulkan, dx12, metal, gl
VECTORCRAFT_GPU_SKIP	Set by the app when it starts again without a graphics adapter that failed (see Desktop graphics processor)
RUST_LOG	Log levels for standard error and the log file (see Logs)

macOS: the menu bar

On macOS the menus live in the system menu bar, not in the window's app bar (which keeps the brand mark, Home, the search icon and the workspace switcher next to the traffic lights, centred on the bar by apps/vectorcraft/src/mac_window.rs). --in-window-menus or VECTORCRAFT_IN_WINDOW_MENUS=1 keeps them in the window, as on Windows, Linux and the web; so does a menu bar AppKit refuses to build (logged). ui.inspect says which with nativeMenuBar.

• One menu model. crates/ui-egui/src/native_menu.rs (platform-free, tested on every platform) builds the menu bar from the in-window menus (menus::menu_tree, each item through menus::entry, which the in-window menus draw too) and lays it out the Mac way: the VectorCraft menu holds About, Settings ▸ (one item per Preferences page, General… ⌘K), Language ▸, Appearance ▸ (UI brightness), Services, Hide VectorCraft ⌃⌘H (⌘H stays View › Hide Edges), Hide Others ⌥⌘H, Show All and Quit ⌘Q (the app's own app.quit, so unsaved documents are asked about); those leave Edit and Help. The in-window bar itself never shows the VectorCraft menu (it starts at File, as in Illustrator, on every platform): Language and Appearance have no in-window menu and are synthesized in mac_layout, and Quit is File › Exit in the window, relabelled to Quit in the App menu. Window starts with Minimize ⌃⌘M and Zoom and ends with Bring All to Front, and Help is the system's Help menu (its search field). A system key a command (or a user's shortcut) already has stays the command's, and the log says so.
• The native side is apps/vectorcraft/src/mac_menu.rs: muda (=0.21.1, default features off, macOS only, no unsafe) builds the NSMenus. Labels, enabled and checked are updated in place when anything they show may have changed (a command ran, the document, its history or selection changed, a click or a key press); a change of structure (a recent file, the language, a shortcut) rebuilds the menus. While an interaction is open (for example a move, scale or shape drag, a dialog's preview or the font menu's preview), the app updates them for the document's changes only when the interaction begins and when it ends.
• Keys stay with egui. AppKit runs a menu's key equivalents before the window sees the key, so the item's key goes back to egui as the key press it was (⌘X/⌘C/⌘V as egui's Cut/Copy/Paste events), through raw_input_hook: shortcuts::handle runs it once, user shortcuts apply, and a focused text field keeps ⌘A, ⌘C, ⌘V and ⌘Z. A click runs the item like an in-window click. Bare keys and ⌥/⇧ chords are never key equivalents (they type).
• Built and clippy-checked for aarch64-apple-darwin and x86_64-apple-darwin from any host: cargo clippy -p vectorcraft --target aarch64-apple-darwin --all-targets -- -D warnings.

Linux: Wayland and X11

The window runs natively on Wayland (eframe's wayland feature) and on X11. On machines with two GPUs it renders on the one the desktop runs on unless Preferences say otherwise; see Desktop graphics processor (#502). The system clipboard (apps/vectorcraft/src/clipboard.rs) is arboard with its wayland-data-control feature:

• Clipboard: under Wayland arboard talks to the compositor through the data-control protocol (wlroots compositors such as Sway and Hyprland, KDE Plasma), so bitmaps (image/png), SVG markup and text copied in any app paste (#398). Where the compositor lacks the protocol (GNOME's Mutter, arboard#223), arboard falls back to the X11 clipboard through XWayland, which only holds what X11 apps copied. egui's own text paste into fields goes through smithay-clipboard and works either way.
• Clipboard owners that never answer (#510): reading the clipboard waits on the app that owns it: arboard gives up on an X11 owner after 4 s, and a Wayland read waits for the owner to send its data. So on Linux the check that enables the Paste menu items runs on a background thread with a second clipboard handle (crates/ui-egui/src/clipboard_probe.rs, installed as Services::clipboard_probe), only while nothing is copied in the app and a document is open, and the window keeps drawing. A paste itself still reads on the UI thread, so pasting from such an owner waits for it once. Windows and macOS keep the check on the UI thread: Windows only asks which formats the clipboard holds, macOS asks the pasteboard server.
• Copied files: files copied in a file manager (text/uri-list; CF_HDROP on Windows, file URLs on macOS) paste as the first one that is art (SVG, PDF, EMF/WMF or a bitmap), before the clipboard's other formats (which include the files' paths as text).
• Dropping files on the window does not work under Wayland: winit 0.30, which eframe 0.36 runs on, has no Wayland drag and drop (winit#1881, added in winit 0.31; egui#1563), so no dropped_files arrive. Until eframe moves to winit 0.31: copy the files in the file manager and paste them, use File › Place or Open, or open the window through XWayland, where drops work: set Preferences › Performance › Linux Display Server to X11 (XWayland) and restart (#1151), or start the app with WAYLAND_DISPLAY= vectorcraft. The preference (linuxDisplayServer, read at startup in apps/vectorcraft/src/main.rs, shown on Linux only) has winit open the window on X11 (EventLoopBuilderExtX11::with_x11) when the session is Wayland, DISPLAY is set and the X11 libraries winit loads are installed (apps/vectorcraft/src/xwayland.rs reads ldconfig -p and the usual library directories); otherwise the window opens on Wayland and the log says why. Unlike clearing WAYLAND_DISPLAY, it leaves the clipboard on the compositor's own.
• Pens and pen displays under Wayland (#491): winit 0.30 doesn't bind the Wayland tablet protocol (zwp_tablet_v2; tablet input arrives in winit 0.31, winit#4318, egui#7731). Since Plasma 6.3, KWin no longer turns tablet input into pointer input for such apps (kwin!6336): the pen moves the compositor's cursor over the window, but the app gets no motion or presses and shows none of its own cursors. Until eframe moves to winit 0.31, either run the app under XWayland, which supports the tablet protocol and hands the pen to X11 apps as a pointer (Preferences › Performance › Linux Display Server › X11 (XWayland), WAYLAND_DISPLAY= vectorcraft, or env -u WAYLAND_DISPLAY vectorcraft; for a desktop launcher, put env WAYLAND_DISPLAY= before the command in its Exec= line), or turn KWin's deprecated emulation back on for the whole session by setting KWIN_WAYLAND_EMULATE_TABLET=1 in KWin's environment (for example in a file under ~/.config/environment.d/ or in /etc/environment) and logging in again. The pen then works as a mouse, without pressure: winit 0.30 reads pen pressure on Windows only (Windows Ink, which reaches the Liquify tools' Use Pressure Pen). Other compositors that don't emulate a pointer for tablets behave the same way.

Fonts: craft-fonts (optional build input)

Font files are never committed to this repository. Fonts shared by the Crafting Apps live in storytold/craft-fonts; the rules are in craftrules standards/fonts.md. To add a font, add it there. (The Latin fonts in assets/fonts/ predate the rule and stay.)

VectorCraft builds, tests and runs without craft-fonts. To embed its Japanese fonts (BIZ UDPGothic for UI text, Shippori Mincho and BIZ UDMincho for document text), point the CRAFT_FONTS_DIR build option at a checkout:

git clone https://github.com/storytold/craft-fonts ../craft-fonts
CRAFT_FONTS_DIR="$PWD/../craft-fonts" cargo run --release -p vectorcraft
CRAFT_FONTS_DIR="$PWD/../craft-fonts" cargo xtask ci   # also runs the Japanese-glyph tests

• crates/text/build.rs reads the checkout's fonts/manifest.txt and embeds every font it lists as vectorcraft_text::CRAFT_FONTS (empty without CRAFT_FONTS_DIR). Give it an absolute path: build scripts run in the crate's directory (a relative path is taken from the workspace root as a convenience, but CI and the docs always use absolute paths). Nothing is downloaded, and craft-fonts is never a Cargo.toml dependency. A bad path is a build warning, or an error with CRAFT_FONTS_REQUIRED=1 (release builds).
• Web (wasm32) builds embed only BIZ UDPGothic Regular (+4.7 MB of .wasm), to stay well under static hosts' per-file limits (Cloudflare Pages: 25 MiB). Shippori Mincho, which this repo used to embed everywhere, was 8.7 MB, so the web build is still smaller than before.
• Document text: the Japanese faces join the font database after the bundled fonts (Mincho first), so they are the fallback for Japanese after the requested font; installed system fonts come after. Noto Sans Thai (when the checkout has it) is the fallback for Thai where no Thai font is installed, and the web build fetches it before the app starts (crates/text/web-fonts.txt).
• UI: theme::install_fonts adds them at the end of every egui family (BIZ UDPGothic first), after the UI fonts and before the installed fonts ui_fonts.rs discovers for other scripts.
• Tests that need Japanese glyphs skip with a message when built without craft-fonts. The FreeBSD CI job and every release job (release.yml) check craft-fonts out at a pinned commit; release packages carry each embedded font's OFL-<family>.txt.

Arabic fonts and the web build

Desktop builds load craft-fonts' Arabic families into the document font database (Noto Sans Arabic first, the fallback for Arabic text; the others are picked by name).

The web build doesn't embed them (wasm size). Instead crates/text/web-fonts.txt lists the faces it fetches from beside the wasm, startup (before the app starts) or background (after):

• crates/text/build.rs turns the list into vectorcraft_text::WEB_FONTS (URL fonts/<sha16>/<file> and the SRI hash, from the craft-fonts manifest).
• cargo xtask web-fonts (xtask/src/web_fonts.rs), the Trunk post_build hook, copies the files there, checking each one's SHA-256. A listed face the checkout lacks is skipped with a warning, as in build.rs, so an older craft-fonts just means fewer fonts.
• apps/vectorcraft-web/src/fonts.rs fetches and registers them, logging web font … for any that fail.

Try it: cd apps/vectorcraft-web && CRAFT_FONTS_DIR=$PWD/../../../craft-fonts trunk serve. To serve another craft-fonts face on the web, add a line to web-fonts.txt.

Localisation

Strings in code stay English and are the default lookup keys. crates/ui-egui/src/i18n maps them to display text at render time from one catalog per language (i18n/<code>.tsv; the format is documented in the header of zh-hant.tsv). Command ids, menu paths used for logic, ui.menu.list, the control channel, the CLI and MCP always use the English ids and labels, so agents and scripts never see translated text.

Languages shipped: English (en, the source), Traditional Chinese (zh-hant, complete, in the vocabulary used in Taiwan; zh-TW, zh-HK, zh-MO and zh-Hant-* locales all resolve to it), Simplified Chinese (zh-hans, complete, in the vocabulary used in mainland China; zh-CN, zh-SG, zh-Hans-* and a bare zh resolve to it, so the two scripts never mix), Japanese (ja, complete), Korean (ko, complete; every ko-* locale resolves to it; a count takes no plural, and Hangul is drawn with an installed system font), Vietnamese (vi, complete; every vi-* locale resolves to it; a count takes no plural, so plurals have one form), German (de, complete; de-DE, de-AT, de-CH and every other de-* locale resolve to it), Spanish (es, complete, in neutral international Spanish; every es-* locale such as es-ES, es-MX, es-AR or es-419 resolves to it), French (fr, complete; fr-FR, fr-BE, fr-CA, fr-CH and every other fr-* locale resolve to it), Italian (it, complete; it-IT, it-CH and every other it-* locale resolve to it), Russian (ru, complete; every ru-* locale such as ru-RU, ru-BY or ru-KZ resolves to it), Ukrainian (uk, complete; uk-UA, uk_UA.UTF-8 and every other uk-* locale resolve to it; integer plurals use one/few/many), Hungarian (hu, complete; hu-HU and every other hu-* locale resolve to it; a count takes the singular, so plurals have one form), Polish (pl, complete; pl-PL and every other pl-* locale resolve to it; plurals use one/few/many, with 21, 31 … taking many), Czech (cs, every menu label) and Brazilian Portuguese (pt-br, every menu label and every tl! literal). Untranslated text falls back to English until its rows are added.

• tl!("…") translates a literal into the language the UI is drawn in; i18n::t(s) is the same for a &str. tr(lang, s) takes the language; tr_ctx when one English word needs different translations; tr_id(lang, command_id, label) for menu items (keyed by command id, English label as the fallback); tn / trn(lang, n, one, other) for plurals; fmt fills {name} placeholders, which a translation may reorder.
• The shared widgets (widgets::check, dropdown, menu_item, the buttons, label_row, tooltips of icon_button…), the menus, the dock, the toolbar, the dialog frame and panels::empty_state translate the text they are given, so a panel mostly needs its literals wrapped in tl! to be covered by the tests.
• The language is Edit › Preferences › User Interface › Language or, on macOS, VectorCraft › Language (the app.language UI command, {lang: auto|<code>}); both set the interfaceLanguage preference (auto or a language code; auto follows the system locale: VECTORCRAFT_LOCALE, then LC_ALL/LC_MESSAGES/LANG/LANGUAGE, the macOS preferred languages, the Windows user locale; on the web, ?lang=<code> in the address, then the browser's navigator.languages). The Preferences dialog previews the chosen language before OK.
• To add a language: add <code>.tsv and one row in i18n::LANGUAGES (code, native name, catalog, plural rule). The Language menu, the dropdown, locale matching and the catalog tests (well-formed, no duplicates, placeholders and ellipses agree, command ids exist, every row of a partial catalog is a string the UI shows, the UI fonts have every glyph, no Simplified characters in zh-hant) pick it up. Set complete_menus once every menu string and tl! literal is translated; i18n::tests then enforce it (VECTORCRAFT_I18N_DUMP=strings.txt cargo test -p vectorcraft-ui-egui dump_source_strings lists them).
• Translations are clean-room: written from the meaning of the English text in ordinary vocabulary, never from another product's localisation resources. Product and technology names stay in Latin letters.
• Status-bar messages and errors stay English where they are made (app.ui.status, EngineError: the control channel, MCP and tests read them) and are translated only where the status bar draws them (i18n::msg). @msg catalog rows hold a whole message or a template such as Couldn't open {name}: {e}; {_1}, {_2} … stand for the format string's {}, and the values in the placeholders are translated in turn (the reason after : {e} is often a message too). Czech, German, Spanish, French, Hungarian, Italian, Japanese, Korean, Polish, Russian, Ukrainian and Vietnamese cover every message literal the test scan finds (complete_languages_translate_every_message, languages listed in COMPLETE_MESSAGES): a new Err("…"), Other(…), #[error(…)] or status(…) message needs a row in each of those catalogs (VECTORCRAFT_I18N_DUMP_MESSAGES=messages.txt cargo test -p vectorcraft-ui-egui complete_languages_translate_every_message lists them all). Other languages show messages in English until they add @msg rows.
• Not translated on purpose: names that are user data (layers, swatches, fonts, documents), the tab title's colour mode, command ids and parameter names inside messages. Not done yet: locale-aware number and date formats, right-to-left layout. Chinese and Japanese UI text is drawn with craft-fonts' BIZ UDPGothic when the build embeds it (see Fonts above), else with an installed system font; the glyph test checks Latin and Cyrillic catalogs always and the CJK ones only with craft-fonts. A Traditional Chinese UI font is still to be added to craft-fonts for the web build.

Vendor names gate

cargo xtask brands (part of cargo xtask ci) fails when user-visible text names another vendor's products or company: string literals in Rust sources (command labels and params docs, menus, panels, MCP tool definitions), Cargo.toml descriptions and packaging files. Comments and test code are not checked. Say "the reference app" or name the feature itself. A line that must keep an old name, such as an alias that files or preferences from earlier versions still use, carries a brand-ok comment.

Robustness: VectorCraft never crashes

A crash takes the user's unsaved work with it, and much of what the app reads is untrusted: SVG, PDF, .ai and .vectorcraft files, pasted data, MCP and control-channel messages, command parameters. Shipped code therefore never panics. Anything that can fail returns Result (or Option), the caller handles or propagates it, and the user sees an error message.

Enforced by lints

Cargo.toml denies these clippy lints for the whole workspace, and cargo xtask ci runs clippy with -D warnings. The gate targets the current stable Rust (rust-version in Cargo.toml is only the minimum that builds the app, and no toolchain is pinned): when a new stable adds lints, they are fixed in the code:

Banned in shipped code	Use instead
x.unwrap(), x.expect("…")	x?, x.ok_or(err)?, let Some(v) = x else { return … }, if let, unwrap_or / unwrap_or_default / unwrap_or_else
v.last().unwrap(), v.pop().unwrap()	if let Some(l) = v.last_mut(), let Some((last, rest)) = v.split_last() else { … }
panic!, unreachable!() in a match arm	return an error (EngineError::Other, bad(C, "…")) or a sensible default
todo!, unimplemented!	don't merge unfinished paths; return an error that says what isn't supported

clippy.toml allows unwrap, expect and panic inside #[test] and #[cfg(test)] code. Integration-test files under tests/ and examples/, and the testkit crate, opt out with #![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]. Tests use panic!("…") instead of unreachable!().

Not caught by lints: avoid implicit panics too

• Indexing and slicing: v[i] and &s[a..b] panic when out of range. When the index comes from data (a file, a parameter, another document), use v.get(i) / s.get(a..b). Slicing a &str also panics off a UTF-8 boundary.
• Arithmetic: integer division or % by zero, usize subtraction that can go below zero (write i + 1 == n instead of i == n - 1, or use saturating_sub), and as casts from non-finite floats.
• Unbounded work: cap counts, sizes and allocations read from input. Image dimensions, repeat counts, line breaks and recursion depth all need a limit.
• Encoders and decoders: propagate their errors. Writing an empty file is a silent failure, not a fix.

Don't silence the lint by discarding errors. let _ = … and .ok() are for failures that really don't matter, with a comment saying why.

The safety net

vectorcraft_engine::guard::catch_panic wraps every entry point:

• Session::execute restores the active document, selection and interaction as they were before the top-level command and returns EngineError::Internal.
• Tool events (Session::pointer, tool_key, tool_text) reset the tool and cancel its drag.
• The MCP server answers the request with a JSON-RPC internal error and keeps serving.
• VectorcraftApp::logic and ui lose one frame and show the error in the status bar; each control-channel request is guarded on its own.

The net exists for bugs, not as a substitute for Result. On wasm a panic aborts the app, so the web build has no net at all.

Fuzzing

Untrusted input has property tests that must never panic:

• crates/engine/tests/import_fuzz.rs: garbage, hostile and mutated SVG and PDF, and swatch (.vcswatches, .gpl, .ase), graphic style (.vcstyles) and flattener preset (.vcflattener) libraries, loaded and used, then rendered and exported.
• crates/engine/tests/command_sweep.rs: every command with junk parameters.
• crates/format/tests/prop_format.rs: garbage and mutated .vectorcraft files.
• crates/mcp/tests/protocol_props.rs: malformed MCP messages.

CI runs a few dozen cases each. Before touching an importer, run a deeper search, e.g. PROPTEST_CASES=20000 cargo test --release -p vectorcraft-engine --test import_fuzz. When it finds a panic, fix the code and add the input as a regular test.

Bidirectional type

Point, area and path type lay out Hebrew and Arabic with the Unicode bidirectional algorithm (unicode-bidi, in crates/text/src/layout.rs). Each paragraph's base direction is its ParaStyle::direction (Paragraph panel › Left-to-Right / Right-to-Left Paragraph Direction, shown with Preferences › Type › Show Indic Options; text.setFormat {direction}), else its first strong character. Text is shaped in logical order, right-to-left runs right to left (shape.rs splits segments by bidi level and script), lines are broken in logical order and then each line's whole shaping clusters are put in visual order. Stored text, undo and style ranges stay logical; the caret, selection, hit testing and arrow keys follow the visual order. A paragraph with nothing right to left in it skips the algorithm, so plain text pays nothing for it.

Alignment buttons are physical (Align Left is left in either direction). New type (text.create, the Type tools) is aligned Justify::Auto, the start of each paragraph's direction: Hebrew grows to the left of a point type's anchor. Imported text keeps its own alignment, and SVG import pins the direction SVG implies (left to right unless direction: rtl).

Vertical type keeps its logical order down the column. SVG export outlines text with right-to-left lines (with a warning) until it is written with direction/unicode-bidi; PDF and raster exports use the laid-out glyphs. No font is bundled for these scripts: the installed fonts' fallback covers them (the web build needs a font with that coverage).