Status and roadmap

Tessel is at version 0.1. It’s young: the core of the language and its UI toolkit work, and they’re enough to write real apps (the Tessel IDE is one), but plenty is missing, and details of the language may still change. This page is an honest list of where things stand.

What works today

• The language: structs and enums (with methods), functions and closures, lists and dictionaries, optionals, if, for and match, and value semantics with copy-on-write. Programs made of several files.
• The compiler: type checking with clear error messages, and native code through LLVM. Built apps are single executables that need nothing else installed.
• Platforms: macOS (11 and later) and Windows. Both are built and tested on every change. There’s no Linux support yet.
• UI: windows, HiDPI screens, state and bind, stacks, Scroll, Text, Button, TextField, Toggle, Picker, TabView, CodeEditor with syntax colors, Divider, about 60 built-in icons, SVG, PNG and JPEG pictures, text written in Markdown, keyboard shortcuts, hover and pressed states, and the layout and styling modifiers.
• Looks: light and dark appearance that follows the system, colors of your own, and animation of views that move, resize or fade.
• Text editing: selecting with the mouse and keyboard, word and line movement, copy, cut, paste, undo and redo, Tab between fields, and input methods (Chinese, Japanese, Korean, accents with dead keys).
• Background work: timers (after and every), HTTP requests, downloads and WebSockets, running other programs, and heavy computations on another thread (background), all with completion blocks that run on the UI thread. They work in programs with only fn main too.
• Language: structs, enums with values, interfaces, generics, closures, optionals, errors with Result and try, tuples and sets, for and while loops with break and continue, and programs split over any number of files, with modules (import, public, private) for code shared between programs.
• Standard library: files and folders, JSON and binary encoding of your own types, Data for raw bytes, dates and times with time zones and calendar arithmetic, random numbers, the clipboard, reading standard input and writing to standard error, and many methods for strings, numbers and lists.
• Tools: the tessel command, a REPL (tessel repl), hot reload (tessel run --hot, and “Reload on save” in the IDE), the Tessel IDE (with this documentation built in), a VS Code extension, a language server for other editors, app bundles on macOS, and a headless mode for testing apps and taking screenshots.

Known limitations

Note

These are the main gaps you may run into today.

• Debugging: there is no debugger with breakpoints or stepping yet. Runtime errors show a message and the place in your code, which you can click in the IDE’s console, and print output appears there too.
• Keyboard: Tab moves between text fields, but buttons, toggles and pickers can’t be used from the keyboard.
• Appearance: animation covers moving, resizing and fading; there are no springs or custom curves, and a view that disappears goes at once. There’s no accessibility support (screen readers) yet.
• Packaging: tessel build --bundle makes a .app on macOS, with your icon.png as its icon, but apps aren’t code signed and there are no installers.
• Editor support: the language server reports errors, shows types on hover and completes code, but doesn’t offer go-to-definition or rename.
• Installation: packages exist for Apple silicon Macs and 64-bit Windows only (no Intel Macs yet). The macOS package is signed and notarized; the Windows one isn’t signed yet, so Windows SmartScreen may warn about a downloaded tessel.exe.

Planned

These are the next areas of work. None of them has a date.

Area	Plans
App polish	Accessibility, using every control from the keyboard, richer animation.
Standard library	Filling gaps as apps need them.
Language	Packages: installing shared modules by name, with versions.
Packaging	Code signing and installers.
Debugging	Stepping through code with breakpoints, building on the clickable errors and console the IDE has today.

Tessel’s goals and the reasons for its design are on Tessel’s design.