83 lines
2.7 KiB
Rust
83 lines
2.7 KiB
Rust
use std::collections::{HashMap, HashSet};
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use std::io::{self, Write};
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use crossterm::cursor::MoveTo;
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use crossterm::style::Print;
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use crossterm::terminal::{Clear, ClearType};
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use crossterm::QueueableCommand;
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use unicode_segmentation::UnicodeSegmentation;
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use unicode_width::UnicodeWidthStr;
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/// Measures and stores the with (in terminal coordinates) of graphemes.
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#[derive(Debug, Default)]
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pub struct WidthDB {
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pub active: bool,
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known: HashMap<String, u8>,
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requested: HashSet<String>,
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}
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impl WidthDB {
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/// Determine the width of a grapheme.
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///
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/// If the width has not been measured yet, it is estimated using the
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/// Unicode Standard Annex #11.
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pub fn grapheme_width(&mut self, grapheme: &str) -> u8 {
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assert_eq!(Some(grapheme), grapheme.graphemes(true).next());
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if !self.active {
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return grapheme.width() as u8;
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}
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if let Some(width) = self.known.get(grapheme) {
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*width
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} else {
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self.requested.insert(grapheme.to_string());
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grapheme.width() as u8
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}
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}
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/// Determine the width of a string based on its graphemes.
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///
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/// If the width of a grapheme has not been measured yet, it is estimated
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/// using the Unicode Standard Annex #11.
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pub fn width(&mut self, s: &str) -> usize {
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if !self.active {
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return s.width();
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}
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let mut total: usize = 0;
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for grapheme in s.graphemes(true) {
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total += if let Some(width) = self.known.get(grapheme) {
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(*width).into()
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} else {
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self.requested.insert(grapheme.to_string());
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grapheme.width()
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};
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}
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total
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}
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/// Whether any new graphemes have been seen since the last time
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/// [`Self::measure_widths`] was called.
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pub fn measuring_required(&self) -> bool {
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self.active && !self.requested.is_empty()
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}
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/// Measure the width of all new graphemes that have been seen since the
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/// last time this function was called.
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///
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/// This function measures the actual width of graphemes by writing them to
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/// the terminal. After it finishes, the terminal's contents should be
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/// assumed to be garbage and a full redraw should be performed.
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pub fn measure_widths(&mut self, out: &mut impl Write) -> io::Result<()> {
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if !self.active {
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return Ok(());
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}
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for grapheme in self.requested.drain() {
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out.queue(Clear(ClearType::All))?
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.queue(MoveTo(0, 0))?
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.queue(Print(&grapheme))?;
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out.flush()?;
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let width = crossterm::cursor::position()?.0 as u8;
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self.known.insert(grapheme, width);
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}
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Ok(())
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}
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}
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