TUI Design System
Design around the user's repeated action, the data they must keep in view, and the terminal capabilities actually available. Keep input responsive under slow I/O and make selection, focus, and operation state explicit.
Primary documentation checked: 2026-09-04. Framework APIs change; use the project's versions. Follow the project's visual identity (SilkCircuit Neon for Bliss's personal tools) rather than treating an example palette as a universal theme.
Choose the Layout from the Work
Read app-patterns.md [blocked] for examples and tradeoffs. Read visual-catalog.md [blocked] only when selecting glyphs, borders, charts, or indicators.
Responsive Behavior
Use constraints and content priorities. Keep the selected item visible while collapsing secondary panels; preserve state when they reappear. Recompute layout on resize without treating a zero-sized transient area as an error. Clamp scrolling after filtering, deletion, or a smaller viewport.
Test narrow, ordinary, and wide layouts, including rapid resizing. The minimum usable size follows the task; 80x24 is a useful test case, not permission to disable a picker that would work in 40 columns. A size message should retain quit and recovery input.
Input, Focus, and Editing
Maintain one owner for input parsing. With Crossterm, do not mix EventStream with read/poll, or run competing readers. Handle key press, repeat, and release deliberately; one physical press must not submit twice.
Enhanced keyboard protocols can distinguish keys that legacy terminals encode identically. Negotiate support and retain usable fallback bindings. Never assume Ctrl+I differs from Tab or Ctrl+M from Enter everywhere. Treat bracketed paste as a text event; pasted newlines must not accidentally submit destructive commands.
Raw mode can disable the terminal's normal signal handling. Implement Ctrl+C and suspend/resume deliberately through the framework; do not assume the OS will handle them unchanged. Restore terminal state before handing control to an editor, pager, shell, or suspended process, then reacquire it and redraw.
Show a short footer for currently available actions and a contextual help view. Keep essential instructions visible while a task is running. Durable errors need a retrievable location; a disappearing toast cannot be the only record.
State and Async Work
Separate input events, state transitions, effects, and rendering. Render a snapshot of state without starting network calls or mutating the domain model from a drawing function.
Batch state updates and render changed frames. Coalesce replaceable visual snapshots, not audit events or mutations. Diagnose queue growth, indexing, and allocation costs before dropping data or capping concurrency.
Terminal Capability Policy
Explicit application settings take precedence. In automatic mode, respect a non-empty NO_COLOR before color detection. A color override can opt back in deliberately; disabling color need not disable bold, underline, layout, or every terminal feature.
Truncate only at grapheme boundaries, accounting for wide cells, combining marks, variation selectors, and emoji sequences. Width libraries and emulators can disagree; test representative user text and offer ASCII indicators where rendering is uncertain.
Treat filenames, logs, and remote strings as untrusted display data. Escape control sequences before writing them through raw output APIs; otherwise a displayed value can move the cursor, change a title, or invoke an OSC operation. Use the framework's supported text/sanitization path.
Terminal queries share the input stream with keystrokes. Let one parser correlate replies, limit waiting for unsupported queries, and choose a fallback without swallowing user input.
Visual Hierarchy and Accessibility
Define semantic slots such as foreground, muted text, focus, selection, warning, and error. Keep theme values out of widget code. Use stable spacing and labels before introducing more borders. Provide dark and light variants when the application sets its own background; transparent/default backgrounds need testing against the user's theme.
Pair status colors with text or shape. Use focus indicators that survive monochrome mode, and avoid dimming important values until they become unreadable. WCAG's 4.5:1 normal-text contrast is a useful design target, but terminal font size and ANSI colors are user-controlled; a bold terminal heading does not automatically qualify for the large-text exception. Do not claim formal accessibility compliance from a palette alone.
Provide a plain or linear presentation when a full-screen interface defeats screen-reader navigation. Meaningful labels, keyboard access, and a non-animated mode still need testing with the intended terminal and assistive technology. Avoid blinking warnings or rapidly flashing status. Let users reduce motion; animation must not delay input or hide the final state.
Rendering and Terminal Lifecycle
Use the framework's buffered rendering and cell diffing. Batch writes; use synchronized output only when supported and always pair begin/end even on errors. A single write is not proof of atomic rendering, and synchronized output is an enhancement rather than a prerequisite for a usable TUI.
Render on state changes or an active animation deadline. Measure input latency, output bandwidth, and redraw cost under the intended data rate, including SSH and multiplexers. Choose a refresh cadence for the actual workload; do not impose a universal FPS cap or artificially delay streamed text.
Acquire terminal modes through a scoped owner and restore everything the app enabled: raw mode, alternate screen, cursor visibility, mouse capture, bracketed paste, and keyboard protocol state. Cover normal exit, initialization failure, exceptions/panics, and handled signals. A framework restoration helper may cover only a subset; check its contract. SIGKILL cannot run cleanup.
Verification That Changes Confidence
Use deterministic state-transition tests for selection after deletion, stale async results, modal focus restoration, and cancelled operations. Use the framework's test backend for layout boundaries; inspect at least one real PTY session because snapshots do not exercise terminal modes or input protocols.
Exercise launch, typing, paste, resize, modal open/close, slow or failed I/O, and exit. Include light/dark themes, color disabled, wide/combining text, and the actual supported terminal/multiplexer path. After exit, verify the shell cursor and echo behavior are restored. Expand the matrix when a portability requirement or failure justifies it.
Anti-Patterns
Primary Sources
Checked 2026-09-04: Ratatui application patterns, Ratatui restoration contract, Crossterm input ownership, kitty keyboard protocol, NO_COLOR, Unicode grapheme segmentation, and contrast guidance.
The state-ownership and verification guidance is engineering synthesis from these contracts, not a claim that a protocol guarantees application correctness.
What This Skill is NOT
- Not a framework API manual or a mandate to adopt a new toolkit.
- Not a reason to add animation, icons, or modes to a simple picker.
- Not a substitute for testing the actual terminal and accessibility path.
