Valdemar Lorenzen
97 lines
3.2 KiB
Rust
97 lines
3.2 KiB
Rust
use std::collections::BTreeMap;
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use unicode_segmentation::UnicodeSegmentation;
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use unicode_width::UnicodeWidthStr;
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use crate::tui::TAB_WIDTH;
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/// Terminal-cell coordinates in the original source line, including its tab stops.
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#[derive(Clone, Copy, Debug, Eq, PartialEq)]
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pub(crate) struct Segment {
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pub start: usize,
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pub end: usize,
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}
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#[derive(Default)]
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pub(crate) struct WrapCache {
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key: Option<(usize, u64)>,
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width: usize,
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rows: BTreeMap<usize, Vec<Segment>>,
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}
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impl WrapCache {
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pub(crate) fn prepare(&mut self, key: (usize, u64), width: usize) {
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let width = width.max(1);
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if self.key != Some(key) || self.width != width {
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self.rows.clear();
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self.key = Some(key);
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self.width = width;
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}
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}
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pub(crate) fn segments(&mut self, row: usize, text: &str) -> &[Segment] {
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let width = self.width.max(1);
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self.rows.entry(row).or_insert_with(|| {
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let mut segments = Vec::new();
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let mut start = 0;
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let mut column = 0;
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let mut word_boundary = 0;
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let mut content_end = 0;
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for grapheme in text.graphemes(true) {
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let cells = if grapheme == "\t" {
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TAB_WIDTH - column % TAB_WIDTH
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} else {
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UnicodeWidthStr::width(grapheme)
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};
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if column + cells - start > width && column > start {
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let end = if word_boundary > start {
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word_boundary
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} else {
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column
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};
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segments.push(Segment { start, end });
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start = end;
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if column + cells - start > width && column > start {
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segments.push(Segment { start, end: column });
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start = column;
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}
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}
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if grapheme == "\t" {
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// Tabs are expanded cells, so even a one-column pane preserves them.
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while column + cells - start > width {
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let end = start + width;
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segments.push(Segment { start, end });
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start = end;
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}
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}
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column += cells;
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if !grapheme.chars().all(char::is_whitespace) {
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content_end = column;
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} else if content_end > start {
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// A word break must not leave only whitespace on this visual row.
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word_boundary = column;
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}
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}
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segments.push(Segment { start, end: column });
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// A full final segment has no spare cell for the insertion caret.
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if column - start >= width {
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segments.push(Segment {
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start: column,
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end: column,
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});
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}
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segments
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})
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}
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}
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pub(crate) fn caret_segment(segments: &[Segment], column: usize) -> usize {
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segments
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.partition_point(|segment| segment.start <= column)
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.saturating_sub(1)
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}
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#[cfg(test)]
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#[path = "../tests/unit/wrap.rs"]
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mod tests;
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