Optimize BidiParagraphs with ASCII fast path (#408)

* Optimize BidiParagraphs with ASCII fast path - Added fast path for ASCII text that avoids BidiInfo allocation - Added some text shaping benchmarks

* refactor: fix clippy warnings and cleanup imports

Cargo.toml

@@ -68,6 +68,10 @@ warn_on_missing_glyphs = []
 name = "layout"
 harness = false
 
+[[bench]]
+name = "text_shaping_benchmarks"
+harness = false
+
 [workspace]
 members = ["examples/*"]
 

benches/text_shaping_benchmarks.rs

@@ -0,0 +1,121 @@
+use cosmic_text as ct;
+use cosmic_text::BidiParagraphs;
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+
+fn bench_ascii_fast_path(c: &mut Criterion) {
+    let mut fs = ct::FontSystem::new();
+    let mut buffer = ct::Buffer::new(&mut fs, ct::Metrics::new(14.0, 20.0));
+    buffer.set_size(&mut fs, Some(500.0), None);
+
+    let ascii_text = "Pure ASCII text for BidiParagraphs optimization testing.\n".repeat(50);
+
+    c.bench_function("ShapeLine/ASCII Fast Path", |b| {
+        b.iter(|| {
+            buffer.set_text(
+                &mut fs,
+                black_box(&ascii_text),
+                &ct::Attrs::new(),
+                ct::Shaping::Advanced,
+            );
+            buffer.shape_until_scroll(&mut fs, false);
+        });
+    });
+}
+
+fn bench_bidi_processing(c: &mut Criterion) {
+    let mut fs = ct::FontSystem::new();
+    let mut buffer = ct::Buffer::new(&mut fs, ct::Metrics::new(14.0, 20.0));
+    buffer.set_size(&mut fs, Some(500.0), None);
+
+    let bidi_text = "Mixed English and العربية النص العربي text for BiDi testing.\nThis tests adjust_levels and combined BiDi optimizations.\n".repeat(30);
+
+    c.bench_function("ShapeLine/BiDi Processing", |b| {
+        b.iter(|| {
+            buffer.set_text(
+                &mut fs,
+                black_box(&bidi_text),
+                &ct::Attrs::new(),
+                ct::Shaping::Advanced,
+            );
+            buffer.shape_until_scroll(&mut fs, false);
+        });
+    });
+}
+
+fn bench_layout_heavy(c: &mut Criterion) {
+    let mut fs = ct::FontSystem::new();
+    let mut buffer = ct::Buffer::new(&mut fs, ct::Metrics::new(14.0, 20.0));
+    buffer.set_size(&mut fs, Some(500.0), None);
+
+    let layout_text = "This is a very long line that will wrap multiple times and stress the reorder optimization through intensive layout processing with comprehensive buffer reuse testing. ".repeat(30);
+
+    c.bench_function("ShapeLine/Layout Heavy", |b| {
+        b.iter(|| {
+            buffer.set_text(
+                &mut fs,
+                black_box(&layout_text),
+                &ct::Attrs::new(),
+                ct::Shaping::Advanced,
+            );
+            buffer.shape_until_scroll(&mut fs, false);
+        });
+    });
+}
+
+fn bench_combined_stress(c: &mut Criterion) {
+    let mut fs = ct::FontSystem::new();
+    let mut buffer = ct::Buffer::new(&mut fs, ct::Metrics::new(14.0, 20.0));
+    buffer.set_size(&mut fs, Some(500.0), None);
+
+    let stress_text = format!("{}\n{}\n{}\n{}\n",
+        "ASCII line for BidiParagraphs optimization. ".repeat(15),
+        "Mixed English + العربية for BiDi optimizations. ".repeat(12),
+        "Very long wrapping line that will trigger reorder optimizations multiple times through intensive layout processing. ".repeat(8),
+        "Cache key generation line for ShapeRunKey optimization testing. ".repeat(10)
+    ).repeat(10);
+
+    c.bench_function("ShapeLine/Combined Stress", |b| {
+        b.iter(|| {
+            buffer.set_text(
+                &mut fs,
+                black_box(&stress_text),
+                &ct::Attrs::new(),
+                ct::Shaping::Advanced,
+            );
+            buffer.shape_until_scroll(&mut fs, false);
+        });
+    });
+}
+
+fn bench_bidi_paragraphs_ascii(c: &mut Criterion) {
+    let ascii_text = "Simple ASCII text\nwith multiple lines\n".repeat(50);
+
+    c.bench_function("BidiParagraphs/ASCII", |b| {
+        b.iter(|| {
+            let paras = BidiParagraphs::new(black_box(&ascii_text));
+            black_box(paras.count());
+        });
+    });
+}
+
+fn bench_bidi_paragraphs_mixed(c: &mut Criterion) {
+    let mixed_text = "Mixed English and العربية text\nwith multiple lines\n".repeat(30);
+
+    c.bench_function("BidiParagraphs/Mixed", |b| {
+        b.iter(|| {
+            let paras = BidiParagraphs::new(black_box(&mixed_text));
+            black_box(paras.count());
+        });
+    });
+}
+
+criterion_group!(
+    benches,
+    bench_ascii_fast_path,
+    bench_bidi_processing,
+    bench_layout_heavy,
+    bench_combined_stress,
+    bench_bidi_paragraphs_ascii,
+    bench_bidi_paragraphs_mixed
+);
+criterion_main!(benches);

src/bidi_para.rs

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
+use alloc::vec::Vec;
 use unicode_bidi::{bidi_class, BidiClass, BidiInfo, ParagraphInfo};
 
 /// An iterator over the paragraphs in the input text.
@@ -11,12 +12,46 @@ pub struct BidiParagraphs<'text> {
 }
 
 impl<'text> BidiParagraphs<'text> {
-    /// Create an iterator to split the input text into paragraphs
-    /// in accordance with `unicode-bidi` behaviour.
+    /// Create an iterator with optimized paragraph detection.
+    /// This version avoids `BidiInfo` allocation for simple ASCII text.
     pub fn new(text: &'text str) -> Self {
-        let info = BidiInfo::new(text, None);
-        let info = info.paragraphs.into_iter();
-        Self { text, info }
+        // Fast path for simple ASCII text - just split on newlines
+        if text.is_ascii()
+            && !text
+                .chars()
+                .any(|c| c.is_ascii_control() && c != '\n' && c != '\r' && c != '\t')
+        {
+            // For simple ASCII, we can avoid `BidiInfo` entirely
+            // Create minimal ParagraphInfo entries for each line
+            let mut paragraphs = Vec::new();
+            let mut start = 0;
+
+            for (i, c) in text.char_indices() {
+                if c == '\n' {
+                    paragraphs.push(ParagraphInfo {
+                        range: start..i,
+                        level: unicode_bidi::Level::ltr(),
+                    });
+                    start = i + 1;
+                }
+            }
+
+            // Add final paragraph if text doesn't end with newline
+            if start < text.len() {
+                paragraphs.push(ParagraphInfo {
+                    range: start..text.len(),
+                    level: unicode_bidi::Level::ltr(),
+                });
+            }
+
+            let info = paragraphs.into_iter();
+            Self { text, info }
+        } else {
+            // Complex text - fall back to full `BidiInfo` analysis
+            let info = BidiInfo::new(text, None);
+            let info = info.paragraphs.into_iter();
+            Self { text, info }
+        }
     }
 }
 

src/buffer.rs

@@ -5,10 +5,12 @@ use alloc::{string::String, vec::Vec};
 use core::{cmp, fmt};
 use unicode_segmentation::UnicodeSegmentation;
 
+#[cfg(feature = "swash")]
+use crate::Color;
 use crate::{
-    Affinity, Align, Attrs, AttrsList, BidiParagraphs, BorrowedWithFontSystem, BufferLine, Color,
-    Cursor, FontSystem, LayoutCursor, LayoutGlyph, LayoutLine, LineEnding, LineIter, Motion,
-    Scroll, ShapeLine, Shaping, Wrap,
+    Affinity, Align, Attrs, AttrsList, BidiParagraphs, BorrowedWithFontSystem, BufferLine, Cursor,
+    FontSystem, LayoutCursor, LayoutGlyph, LayoutLine, LineEnding, LineIter, Motion, Scroll,
+    ShapeLine, Shaping, Wrap,
 };
 
 /// A line of visible text for rendering

src/edit/editor.rs

@@ -1,20 +1,21 @@
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
-#[cfg(not(feature = "std"))]
-use alloc::{
-    string::{String, ToString},
-    vec::Vec,
-};
-use core::{cmp, iter::once};
-use unicode_segmentation::UnicodeSegmentation;
-
 #[cfg(feature = "swash")]
 use crate::Color;
 use crate::{
     Action, Attrs, AttrsList, BorrowedWithFontSystem, BufferLine, BufferRef, Change, ChangeItem,
     Cursor, Edit, FontSystem, LayoutRun, Selection, Shaping,
 };
+#[cfg(feature = "no_std")]
+use alloc::{
+    string::{String, ToString},
+    vec::Vec,
+};
+#[cfg(feature = "swash")]
+use std::cmp;
 
+use core::iter::once;
+use unicode_segmentation::UnicodeSegmentation;
 /// A wrapper of [`Buffer`] for easy editing
 #[derive(Debug, Clone)]
 pub struct Editor<'buffer> {
@@ -583,7 +584,7 @@ impl<'buffer> Edit<'buffer> for Editor<'buffer> {
             Action::Insert(character) => {
                 if character.is_control() && !['\t', '\n', '\u{92}'].contains(&character) {
                     // Filter out special chars (except for tab), use Action instead
-                    log::debug!("Refusing to insert control character {:?}", character);
+                    log::debug!("Refusing to insert control character {character:?}");
                 } else if character == '\n' {
                     self.action(font_system, Action::Enter);
                 } else {

src/edit/syntect.rs

@@ -132,11 +132,11 @@ impl<'syntax_system, 'buffer> SyntaxEditor<'syntax_system, 'buffer> {
         self.syntax = match self.syntax_system.syntax_set.find_syntax_for_file(path) {
             Ok(Some(some)) => some,
             Ok(None) => {
-                log::warn!("no syntax found for {:?}", path);
+                log::warn!("no syntax found for {path:?}");
                 self.syntax_system.syntax_set.find_syntax_plain_text()
             }
             Err(err) => {
-                log::warn!("failed to determine syntax for {:?}: {:?}", path, err);
+                log::warn!("failed to determine syntax for {path:?}: {err:?}");
                 self.syntax_system.syntax_set.find_syntax_plain_text()
             }
         };
@@ -156,7 +156,7 @@ impl<'syntax_system, 'buffer> SyntaxEditor<'syntax_system, 'buffer> {
         {
             Some(some) => some,
             None => {
-                log::warn!("no syntax found for {}", extension);
+                log::warn!("no syntax found for {extension:?}");
                 self.syntax_system.syntax_set.find_syntax_plain_text()
             }
         };

src/edit/vi.rs

@@ -1,7 +1,8 @@
-use alloc::{collections::BTreeMap, string::String};
+#[cfg(feature = "no_std")]
 use core::cmp;
+
+use alloc::{collections::BTreeMap, string::String};
 use modit::{Event, Key, Parser, TextObject, WordIter};
-use unicode_segmentation::UnicodeSegmentation;
 
 use crate::{
     Action, AttrsList, BorrowedWithFontSystem, BufferRef, Change, Color, Cursor, Edit, FontSystem,
@@ -9,6 +10,8 @@ use crate::{
 };
 
 pub use modit::{ViMode, ViParser};
+#[cfg(feature = "swash")]
+use unicode_segmentation::UnicodeSegmentation;
 
 fn undo_2_action<'buffer, E: Edit<'buffer>>(
     editor: &mut E,
@@ -599,7 +602,7 @@ impl<'buffer> Edit<'buffer> for ViEditor<'_, 'buffer> {
     }
 
     fn action(&mut self, font_system: &mut FontSystem, action: Action) {
-        log::debug!("Action {:?}", action);
+        log::debug!("Action {action:?}");
 
         let editor = &mut self.editor;
 
@@ -636,7 +639,7 @@ impl<'buffer> Edit<'buffer> for ViEditor<'_, 'buffer> {
             Action::Unindent => Key::Backtab,
             Action::Motion(Motion::Up) => Key::Up,
             _ => {
-                log::debug!("Pass through action {:?}", action);
+                log::debug!("Pass through action {action:?}");
                 editor.action(font_system, action);
                 // Always finish change when passing through (TODO: group changes)
                 finish_change(
@@ -652,7 +655,7 @@ impl<'buffer> Edit<'buffer> for ViEditor<'_, 'buffer> {
         let has_selection = !matches!(editor.selection(), Selection::None);
 
         self.parser.parse(key, has_selection, |event| {
-            log::debug!("  Event {:?}", event);
+            log::debug!("  Event {event:?}");
             let action = match event {
                 Event::AutoIndent => {
                     log::info!("TODO: AutoIndent");
@@ -813,7 +816,7 @@ impl<'buffer> Edit<'buffer> for ViEditor<'_, 'buffer> {
                             editor.set_cursor(cursor);
                         }
                         _ => {
-                            log::info!("TODO: {:?}", text_object);
+                            log::info!("TODO: {text_object:?}");
                         }
                     }
                     return;
@@ -1006,7 +1009,7 @@ impl<'buffer> Edit<'buffer> for ViEditor<'_, 'buffer> {
                                             }
                                             None
                                         })
-                                        .last()
+                                        .next_back()
                                     {
                                         cursor.index = i;
                                     }

src/font/fallback/mod.rs

@@ -454,7 +454,7 @@ impl<'a> FontFallbackIter<'a> {
                     }
                 }
             }
-            log::debug!("failed to find family '{}'", common_family);
+            log::debug!("failed to find family '{common_family}'");
         }
 
         //TODO: do we need to do this?

src/font/system.rs

@@ -147,7 +147,7 @@ impl FontSystem {
     /// Create a new [`FontSystem`] with a pre-specified set of fonts.
     pub fn new_with_fonts(fonts: impl IntoIterator<Item = fontdb::Source>) -> Self {
         let locale = Self::get_locale();
-        log::debug!("Locale: {}", locale);
+        log::debug!("Locale: {locale}");
 
         let mut db = fontdb::Database::new();
 
@@ -370,7 +370,7 @@ impl FontSystem {
                 #[cfg(all(feature = "std", not(target_arch = "wasm32")))]
                 {
                     let elapsed = now.elapsed();
-                    log::debug!("font matches for {:?} in {:?}", attrs, elapsed);
+                    log::debug!("font matches for {attrs:?} in {elapsed:?}");
                 }
 
                 Arc::new(font_match_keys)