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Document pos_at_coords better.

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Particularly the effect of the `limit_before_line_ending`
parameter.
This commit is contained in:
Nathan Vegdahl 2021-08-07 15:34:01 -07:00 committed by Blaž Hrastnik
parent a2ccfffda1
commit b5223618ed
1 changed files with 16 additions and 7 deletions
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23
helix-core/src/position.rs
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@ -71,18 +71,27 @@ pub fn coords_at_pos(text: RopeSlice, pos: usize) -> Position {
/// Convert (line, column) coordinates to a character index.
///
/// `is_1_width` specifies whether the position should be treated
/// as a block cursor or not. This effects how line-ends are handled.
/// `false` corresponds to properly round-tripping with `coords_at_pos()`,
/// whereas `true` will ensure that block cursors don't jump off the
/// end of the line.
/// If the `line` coordinate is beyond the end of the file, the EOF
/// position will be returned.
///
/// If the `column` coordinate is past the end of the given line, the
/// line-end position will be returned. What constitutes the "line-end
/// position" depends on the parameter `limit_before_line_ending`. If it's
/// `true`, the line-end position will be just *before* the line ending
/// character. If `false` it will be just *after* the line ending
/// character--on the border between the current line and the next.
///
/// Usually you only want `limit_before_line_ending` to be `true` if you're working
/// with left-side block-cursor positions, as this prevents the the block cursor
/// from jumping to the next line. Otherwise you typically want it to be `false`,
/// such as when dealing with raw anchor/head positions.
///
/// TODO: this should be changed to work in terms of visual row/column, not
/// graphemes.
pub fn pos_at_coords(text: RopeSlice, coords: Position, is_1_width: bool) -> usize {
pub fn pos_at_coords(text: RopeSlice, coords: Position, limit_before_line_ending: bool) -> usize {
let Position { row, col } = coords;
let line_start = text.line_to_char(row);
let line_end = if is_1_width {
let line_end = if limit_before_line_ending {
line_end_char_index(&text, row)
} else {
text.line_to_char((row + 1).min(text.len_lines()))