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https://github.com/ratatui-org/ratatui
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perf(reflow): eliminate most WordWrapper allocations (#1239)
On large paragraphs (~1MB), this saves hundreds of thousands of allocations. TL;DR: reuse as much memory as possible across `next_line` calls. Instead of allocating new buffers each time, allocate the buffers once and clear them before reuse. Signed-off-by: Alex Saveau <saveau.alexandre@gmail.com>
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36fa3c11c1
commit
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1 changed files with 47 additions and 31 deletions
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@ -1,4 +1,4 @@
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use std::{collections::VecDeque, vec::IntoIter};
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use std::{collections::VecDeque, mem};
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use unicode_segmentation::UnicodeSegmentation;
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use unicode_width::UnicodeWidthStr;
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@ -34,11 +34,16 @@ where
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/// The given, unprocessed lines
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input_lines: O,
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max_line_width: u16,
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wrapped_lines: Option<IntoIter<Vec<StyledGrapheme<'a>>>>,
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wrapped_lines: VecDeque<Vec<StyledGrapheme<'a>>>,
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current_alignment: Alignment,
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current_line: Vec<StyledGrapheme<'a>>,
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/// Removes the leading whitespace from lines
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trim: bool,
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// These are cached allocations that hold no state across next_line invocations
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pending_word: Vec<StyledGrapheme<'a>>,
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pending_whitespace: VecDeque<StyledGrapheme<'a>>,
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pending_line_pool: Vec<Vec<StyledGrapheme<'a>>>,
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}
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impl<'a, O, I> WordWrapper<'a, O, I>
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@ -50,29 +55,30 @@ where
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Self {
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input_lines: lines,
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max_line_width,
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wrapped_lines: None,
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wrapped_lines: VecDeque::new(),
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current_alignment: Alignment::Left,
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current_line: vec![],
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trim,
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}
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}
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fn next_cached_line(&mut self) -> Option<Vec<StyledGrapheme<'a>>> {
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self.wrapped_lines.as_mut()?.next()
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pending_word: Vec::new(),
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pending_line_pool: Vec::new(),
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pending_whitespace: VecDeque::new(),
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}
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}
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/// Split an input line (`line_symbols`) into wrapped lines
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/// and cache them to be emitted later
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fn process_input(&mut self, line_symbols: impl IntoIterator<Item = StyledGrapheme<'a>>) {
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let mut result_lines = vec![];
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let mut pending_line = vec![];
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let mut pending_line = self.pending_line_pool.pop().unwrap_or_default();
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let mut line_width = 0;
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let mut pending_word = vec![];
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let mut word_width = 0;
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let mut pending_whitespace: VecDeque<StyledGrapheme> = VecDeque::new();
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let mut whitespace_width = 0;
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let mut non_whitespace_previous = false;
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self.pending_word.clear();
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self.pending_whitespace.clear();
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pending_line.clear();
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for grapheme in line_symbols {
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let is_whitespace = grapheme.is_whitespace();
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let symbol_width = grapheme.symbol.width() as u16;
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@ -99,14 +105,14 @@ where
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// append finished segment to current line
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if word_found || trimmed_overflow || whitespace_overflow || untrimmed_overflow {
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if !pending_line.is_empty() || !self.trim {
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pending_line.extend(pending_whitespace.drain(..));
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pending_line.extend(self.pending_whitespace.drain(..));
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line_width += whitespace_width;
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}
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pending_line.append(&mut pending_word);
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pending_line.append(&mut self.pending_word);
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line_width += word_width;
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pending_whitespace.clear();
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self.pending_whitespace.clear();
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whitespace_width = 0;
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word_width = 0;
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}
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@ -121,11 +127,11 @@ where
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if line_full || pending_word_overflow {
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let mut remaining_width = u16::saturating_sub(self.max_line_width, line_width);
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result_lines.push(std::mem::take(&mut pending_line));
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self.wrapped_lines.push_back(mem::take(&mut pending_line));
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line_width = 0;
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// remove whitespace up to the end of line
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while let Some(grapheme) = pending_whitespace.front() {
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while let Some(grapheme) = self.pending_whitespace.front() {
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let width = grapheme.symbol.width() as u16;
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if width > remaining_width {
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@ -134,11 +140,11 @@ where
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whitespace_width -= width;
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remaining_width -= width;
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pending_whitespace.pop_front();
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self.pending_whitespace.pop_front();
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}
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// don't count first whitespace toward next word
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if is_whitespace && pending_whitespace.is_empty() {
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if is_whitespace && self.pending_whitespace.is_empty() {
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continue;
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}
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}
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@ -146,33 +152,43 @@ where
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// append symbol to a pending buffer
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if is_whitespace {
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whitespace_width += symbol_width;
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pending_whitespace.push_back(grapheme);
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self.pending_whitespace.push_back(grapheme);
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} else {
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word_width += symbol_width;
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pending_word.push(grapheme);
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self.pending_word.push(grapheme);
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}
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non_whitespace_previous = !is_whitespace;
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}
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// append remaining text parts
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if pending_line.is_empty() && pending_word.is_empty() && !pending_whitespace.is_empty() {
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result_lines.push(vec![]);
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if pending_line.is_empty()
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&& self.pending_word.is_empty()
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&& !self.pending_whitespace.is_empty()
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{
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self.wrapped_lines.push_back(vec![]);
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}
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if !pending_line.is_empty() || !self.trim {
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pending_line.extend(pending_whitespace);
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pending_line.extend(self.pending_whitespace.drain(..));
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}
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pending_line.extend(pending_word);
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pending_line.append(&mut self.pending_word);
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#[allow(clippy::else_if_without_else)]
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if !pending_line.is_empty() {
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result_lines.push(pending_line);
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self.wrapped_lines.push_back(pending_line);
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} else if pending_line.capacity() > 0 {
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self.pending_line_pool.push(pending_line);
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}
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if result_lines.is_empty() {
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result_lines.push(vec![]);
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if self.wrapped_lines.is_empty() {
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self.wrapped_lines.push_back(vec![]);
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}
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}
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// save processed lines for emitting later
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self.wrapped_lines = Some(result_lines.into_iter());
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fn replace_current_line(&mut self, line: Vec<StyledGrapheme<'a>>) {
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let cache = mem::replace(&mut self.current_line, line);
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if cache.capacity() > 0 {
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self.pending_line_pool.push(cache);
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}
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}
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}
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@ -189,13 +205,13 @@ where
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loop {
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// emit next cached line if present
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if let Some(line) = self.next_cached_line() {
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if let Some(line) = self.wrapped_lines.pop_front() {
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let line_width = line
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.iter()
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.map(|grapheme| grapheme.symbol.width() as u16)
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.sum();
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self.current_line = line;
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self.replace_current_line(line);
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return Some(WrappedLine {
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line: &self.current_line,
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width: line_width,
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