xless

xless is a viewer-first TUI editor for macOS, Linux, and Windows, built in Rust. It opens very large files (100 MB to GB) quickly, stays responsive under heavy operations, and provides a simple, explicit Edit mode (no vim semantics).

Why xless

Most terminal editors either:

• load too much into memory,
• freeze on big logs,
• or expect you to worship modal editing.

xless is optimized for the common workflow: open a huge file, inspect/search it fast, and only edit when you explicitly switch to Edit mode.

Key features

• Fast open for big files (read-mostly mode for very large inputs)
• Viewer-first UX (less-style navigation and search)
• Explicit modes:
  • View mode (default): safe navigation/search
  • Edit mode: predictable editing (nano/FAR-like)
• No full-file copying: piece table (original + add buffer)
• UTF-8 safe editing: operations respect code point boundaries
• Async heavy work: search/highlight/indexing runs in workers, UI stays responsive
• Windowed rendering: renders only the visible viewport

Status

This project is in active development. Core phases (0–7) are implemented: stable TUI lifecycle, piece table model, UTF-8 safety, viewport rendering, basic editor, modes, less-style search, and async job architecture.

Build

Prerequisites

• Rust stable (latest recommended)

Build and run

# Build (optimized)
cargo build --release

# Run
cargo run --release -- path/to/file.txt

Large files and read-mostly mode

For very large files xless can enter read-mostly mode to avoid expensive operations and keep memory usage predictable. In this mode, editing may be disabled or limited by design (viewer-first).

If your build has a specific size threshold (for example 200 MB), document it here. If you changed the threshold in code, update this README accordingly.

Usage

Modes

• View mode (default)

  • Safe navigation
  • Search and match navigation
  • Paging and jumps
  • Designed to behave like a familiar viewer (less/FAR)

• Edit mode

  • Explicitly enabled
  • Normal typing, delete/backspace, line breaks
  • Undo/redo
  • Intended for focused edits, not bulk transformations

The status line shows the current mode and prompts.

Search

• Search is asynchronous to avoid UI freezes on large inputs.
• Matches can be navigated forward/backward.
• After edits, search results are invalidated and must be rerun (prevents stale offsets).

Note: search may support regex depending on the current implementation.

Key bindings

xless intentionally keeps bindings simple and viewer-first. The exact mapping may evolve while the project stabilizes.

View mode (typical)

• Arrow keys: move cursor
• PageUp/PageDown: page navigation
• /: search prompt
• n / N: next/previous match
• g / G: jump to start/end (if implemented)
• q: quit (or via Ctrl-Q, depending on platform)

Edit mode (typical)

• Typing: insert text
• Backspace/Delete: remove text
• Ctrl-S: save
• Ctrl-Z / Ctrl-Y: undo/redo (or other configured bindings)

If your actual bindings differ, update this section to match the code. (Prefer documenting only what is implemented.)

Testing

# Unit tests
cargo test

# Optional: large-file smoke tests (if present in the repo)
./tests/test_large_file.sh

Recommended additional checks:

• Open a multi-hundred-megabyte log file and confirm UI remains responsive during async search.
• Validate behavior on non-UTF-8 input (should remain visible, not disappear).

Roadmap (near-term)

• More robust line/column mapping for long lines and extreme horizontal scroll
• Viewport-only syntax highlighting (tree-sitter “on window”)
• Bulk operations in view mode (filter/export)
• Optional AI-assisted analysis as an external process (kept out of the core editor)

License

Apache-2.0

Copyright Modcrafter © 2026