neco-textview

日本語

UTF-8 text primitives for editor cursors: byte-offset/line-column conversion, selection ranges, and UTF-16 offset mapping.

Primitives

neco-textview gives each text buffer a LineIndex built from its source. From that index you can translate byte offsets to (line, column) positions and back, look up byte ranges for a line, and convert between byte offsets and UTF-16 code-unit offsets for LSP-compatible callers.

Selection tracks anchor and head independently so backward selections are preserved. TextRange is a plain validated [start, end) pair used throughout the API.

Usage

Byte offset to line/column

use neco_textview::{LineIndex, Position};

let text = "abc\ndef\nghi";
let idx = LineIndex::new(text);

let pos = idx.offset_to_position(text, 4).unwrap();
assert_eq!(pos, Position::new(1, 0));

let back = idx.position_to_offset(text, pos).unwrap();
assert_eq!(back, 4);

UTF-16 offset conversion

use neco_textview::Utf16Mapping;

// "aあb": 'あ' is 3 bytes but 1 UTF-16 code unit
let text = "aあb";
let m = Utf16Mapping::new(text);

assert_eq!(m.byte_to_utf16(4).unwrap(), 2); // 'b' at byte 4 → UTF-16 offset 2
assert_eq!(m.utf16_to_byte(2).unwrap(), 4);

Selection

use neco_textview::Selection;

let sel = Selection::new(8, 2); // backward selection
assert!(!sel.is_forward());
let r = sel.range();
assert_eq!(r.start(), 2);
assert_eq!(r.end(), 8);

API

Item	Description
`Position`	`(line, column)` pair using `u32` coordinates
`TextRange`	Validated `[start, end)` byte range
`TextRange::new(start, end)`	Returns `Err` when `start > end`
`TextRange::empty(offset)`	Zero-length range at one offset
`Selection`	Anchor/head pair; preserves direction
`Selection::cursor(offset)`	Collapsed selection at one offset
`Selection::range()`	Normalized `TextRange` regardless of direction
`LineIndex`	Precomputed line-start table for a text buffer
`LineIndex::offset_to_position`	Byte offset → `Position`, validates UTF-8 boundary
`LineIndex::position_to_offset`	`Position` → byte offset
`LineIndex::line_range(line)`	Byte range of a line excluding the trailing `\n`
`LineIndex::line_range_with_newline(line)`	Byte range including the trailing `\n`
`LineIndex::line_of_offset(offset)`	Line number for a byte offset
`Utf16Mapping`	Anchor-based byte ↔ UTF-16 code-unit translator
`Utf16Mapping::byte_to_utf16`	Returns `Err` on non-char-boundary offsets
`Utf16Mapping::utf16_to_byte`	Returns `Err` on surrogate-pair interior offsets
`RangeChange`	Abstract description of a text change: `(start, old_end, new_end)`
`RangeChange::new(start, old_end, new_end)`	Constructor
`RangeChange::start()`	Byte offset where the change begins
`RangeChange::old_end()`	Byte offset where the old text ended
`RangeChange::new_end()`	Byte offset where the new text ends
`TextViewError`	Invalid range, out-of-bounds offset, UTF-8/UTF-16 boundary violations

License

MIT

neco-textview 0.2.0