internal/

Package a11y holds small helpers shared by the widgets' Linearize methods.

Package announce is the state behind a Program's announcements: the on-screen region that shows recent ones for a few seconds, the de-duplicating queue that feeds the accessible-mode transcript, and the sanitising and OSC 99 notification encoding both share.

Package archtest holds the module's import-direction rule: imports go down the tiers below, never up.

Package basetypes holds the small value types that theme and layout share (the Border), so theme can stay a dependency leaf that does not import layout.

Package bidi implements the Unicode Bidirectional Algorithm (UAX #9) for one line of text: it resolves the embedding level of every character and returns the visual order, for display only.

Package braille is the dot-cell drawing shared by the arc and line charts (widgets/chart) and the progress circle (widgets): the 2x4 braille dot encoding, its ASCII shade fallback, and the annulus fill behind Gauge and ProgressCircle.

Package cancelreader is an io.Reader over an *os.File whose blocked Read can be cancelled from another goroutine.

Package capprobe holds the terminal capability probe's wire format: the queries a Program writes at start-up and the parser that turns the replies into a Result.

Package cellcheck runs a model headless under the cell renderer and reports the frames that fell back to the line renderer, for the example corpus tests (spec S11: the cell renderer's fallback rate on the examples is zero).

Package edit is the grapheme- and width-aware text-editing core shared by the input widgets.

Package fsutil is a shared filesystem-listing helper for widgets that browse directories (filepicker, treeview's DirectoryTree builder), so neither duplicates os.ReadDir traversal nor depends on the other.

Package highlight splits source code into classed spans for a set of languages (Go, JSON, shell, YAML, Python, JavaScript, TypeScript, Rust, C, C++, Java, C#, Kotlin, Swift, PHP, Ruby, Lua, HTML, XML, CSS, diff, Markdown, SQL, TOML, INI, Makefile, Dockerfile).

Package isolation holds the module-wide copy-isolation sweep: for every stateful widget Model it snapshots a value copy, drives Update on the original, and asserts the snapshot did not change.

Package ptytest opens pseudo-terminals for tests, using /dev/ptmx and the pty ioctls directly (no dependencies).

Package render is the cell-diffing renderer behind the root package's default renderer.

Package termio holds the implementations of tui.Terminal, the runtime's port to the terminal (size query, raw mode, output virtual-terminal processing): OSTerminal for a real terminal and Fake for tests.

Package testutil holds test helpers shared by the module's packages.

Package vtscreen is a small virtual terminal: it applies the escape sequences a Program writes to a grid of cells, so a test can assert on what a user would see.