Idet Core — editing logic for text editors, without a frontend

Word autocomplete, line moves, word swaps, indentation edits, find and replace, bracket-pair matching, soft wrapping and syntax classification. The editing modules are pure functions — each takes a &str and a character index and returns a new string and cursor position (or a range). Drive them from a terminal UI, an egui widget, or anything else that owns the text buffer and the keybindings.

Built for idet, a terminal editor, and its egui-based sibling gidet, sharing one editing core between two very different frontends.

Modules

• completion — word collection and prefix/whole-word matching for autocomplete (collect_words, current_word, matches).
• edits — insertion, indentation and newline-with-autoindent, plus line-start/line-end lookup (insert, newline_indent, indent_line, dedent_line, line_start_char, line_end_char).
• lineops — moving the current line up or down, and translating between character offsets and line/column coordinates (move_line, line_column, cursor_at).
• wordops — swapping the word at the cursor with an adjacent word (swap).
• brackets — finding the matching bracket for (), [] or {} at or near the cursor (find_matching_bracket).
• search — case-insensitive literal find and replace (find_matches, replace_range, replace_all).
• wrap — laying text out in screen rows at a given width, with or without soft wrapping, and mapping between rows and character positions (rows, visible_end, locate).
• syntax — highlighting classes for a language, read from plain-text definition files under $XDG_CONFIG_HOME/idet/syntax (Syntax, Class, for_path).
• options — the settings both frontends share, stored one option per line under $XDG_CONFIG_HOME/idet/options.conf (Options).
• files (behind the files feature, off by default) — saving and opening a named path on top of document-state, reporting the outcome rather than deciding for the host.
• dialogs (behind the dialogs feature, off by default) — the same operations asking for the path through a native rfd dialog first. Both frontends use it; a host without a desktop session to show a dialog on can take files alone and ask for the path however it likes.
• widget (behind the egui feature, off by default) — a drop-in egui::TextEdit-based multiline editor wired to the modules above: move-line, swap-word, indent/dedent, auto-indent, word autocomplete and find. Enable with idet-core = { version = "...", features = ["egui"] }. Application-specific concerns (save/undo/reload, window chrome, tabs) stay the host's responsibility — the widget only owns the text buffer it's handed each frame.

Design

Every editing operation is a pure function over character indices, not byte offsets — callers don't need to think about UTF-8 boundaries. The modules that do touch the disk (options, syntax, files) are separate from them and, in the case of files, behind a feature. Multi-cursor editing is the caller's responsibility: run the same operation once per cursor, in descending position order, shifting later cursors by the delta each edit produces.