A terminal

go-widgets/tui turns a widget tree into a terminal frame through the cell painter. Standard library only — no x/term, no cgo.

One frame

_ = tui.RenderOnce(os.Stdout, widgets, nil) // nil theme: light

RenderOnceSized(w, cols, rows, widgets, theme) takes the size explicitly; RenderOnce reads COLUMNS and LINES and falls back to 80×24. Reading the environment rather than calling TIOCGWINSZ keeps the package free of per-platform code.

An interactive program

app := tui.NewApp()
app.Root = buildScene()
app.Keys["q"] = func(a *tui.App) { a.Quit() }
app.Keys["Ctrl+C"] = func(a *tui.App) { a.Quit() }
os.Exit(app.Run())

Run enters the alternate screen and raw mode, dispatches input to Root (global key handlers first), follows SIGWINCH, and always restores the terminal — on a panic too. A key handler calls Consume to keep an event from Root; InputTarget sends every unconsumed event to one widget, which is how a command palette swallows typing while it is open. NewFocusRing gives a form Tab and Shift+Tab traversal.

Widgets sized for cells

Most toolkit widgets are designed in pixels: their padding constants count cells under the cell painter and inflate. So tui has its own cell-native set — TextEditor, Entry, Button, CheckButton, RadioButton, Scale, ProgressBar, Sparkline, ListBox, TreeView, Table, MenuBar, Notebook, HSplit, VSplit, Dialog, Dropdown, Spinner and more — where one glyph is one cell. Each is still a toolkit.Widget, so the same instance also draws into pixels.

TextEditor is a read-write code editor: gutter, undo and redo, search and replace, selection, line moves, and syntax highlighting for Go (through go/scanner), JavaScript and TypeScript, Python, Ruby, shell, C and C++, Rust, JSON, YAML, HCL, TOML, LaTeX and Markdown, with no external dependency.

go run ./cmd/tui-widgets | less -R     # every cell-native widget, one per slot
go run ./cmd/tui-widget-explorer       # the same, interactive
go run ./cmd/tui-explorer              # a file browser
go run ./cmd/tui-editor --file=x.go    # a modal editor

The two demo programs are tested end to end in a real pty: real key bytes in, the rendered frame asserted.