Optimize for single-line single-span single-word text

Cargo.toml

@@ -21,6 +21,7 @@ rangemap = "1.4.0"
 rustc-hash = { version = "1.1.0", default-features = false }
 rustybuzz = { version = "0.14", default-features = false, features = ["libm"] }
 self_cell = "1.0.1"
+smallvec = { version = "1.13.2", optional = true }
 smol_str = { version = "0.2.2", default-features = false }
 swash = { version = "0.1.17", optional = true }
 syntect = { version = "5.1.0", optional = true }
@@ -42,6 +43,7 @@ fontconfig = ["fontdb/fontconfig", "std"]
 monospace_fallback = []
 no_std = ["rustybuzz/libm", "hashbrown", "dep:libm"]
 shape-run-cache = []
+small-buffer-opt = ["smallvec"]
 std = [
     "fontdb/memmap",
     "fontdb/std",

src/buffer.rs

@@ -6,9 +6,9 @@ use core::{cmp, fmt};
 use unicode_segmentation::UnicodeSegmentation;
 
 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,
+    BufferVec, Color, Cursor, FontSystem, LayoutCursor, LayoutGlyph, LayoutLine, LineEnding,
+    LineIter, Motion, Scroll, ShapeLine, Shaping, Wrap,
 };
 
 /// A line of visible text for rendering
@@ -203,7 +203,7 @@ impl fmt::Display for Metrics {
 #[derive(Debug)]
 pub struct Buffer {
     /// [BufferLine]s (or paragraphs) of text in the buffer
-    pub lines: Vec<BufferLine>,
+    pub lines: BufferVec<BufferLine>,
     metrics: Metrics,
     width_opt: Option<f32>,
     height_opt: Option<f32>,
@@ -246,7 +246,7 @@ impl Buffer {
     pub fn new_empty(metrics: Metrics) -> Self {
         assert_ne!(metrics.line_height, 0.0, "line height cannot be 0");
         Self {
-            lines: Vec::new(),
+            lines: BufferVec::new(),
             metrics,
             width_opt: None,
             height_opt: None,

src/buffer_line.rs

@@ -3,7 +3,8 @@ use alloc::{string::String, vec::Vec};
 use core::mem;
 
 use crate::{
-    Align, Attrs, AttrsList, Cached, FontSystem, LayoutLine, LineEnding, ShapeLine, Shaping, Wrap,
+    Align, Attrs, AttrsList, BufferVec, Cached, FontSystem, LayoutLine, LineEnding, ShapeLine,
+    Shaping, Wrap,
 };
 
 /// A line (or paragraph) of text that is shaped and laid out
@@ -14,7 +15,7 @@ pub struct BufferLine {
     attrs_list: AttrsList,
     align: Option<Align>,
     shape_opt: Cached<ShapeLine>,
-    layout_opt: Cached<Vec<LayoutLine>>,
+    layout_opt: Cached<BufferVec<LayoutLine>>,
     shaping: Shaping,
     metadata: Option<usize>,
 }
@@ -242,7 +243,7 @@ impl BufferLine {
             let mut layout = self
                 .layout_opt
                 .take_unused()
-                .unwrap_or_else(|| Vec::with_capacity(1));
+                .unwrap_or_else(|| BufferVec::with_capacity(1));
             let shape = self.shape(font_system, tab_width);
             shape.layout_to_buffer(
                 &mut font_system.shape_buffer,
@@ -259,7 +260,7 @@ impl BufferLine {
     }
 
     /// Get line layout cache
-    pub fn layout_opt(&self) -> Option<&Vec<LayoutLine>> {
+    pub fn layout_opt(&self) -> Option<&BufferVec<LayoutLine>> {
         self.layout_opt.get()
     }
 

src/lib.rs

@@ -151,3 +151,10 @@ type BuildHasher = core::hash::BuildHasherDefault<rustc_hash::FxHasher>;
 type HashMap<K, V> = std::collections::HashMap<K, V, BuildHasher>;
 #[cfg(not(feature = "std"))]
 type HashMap<K, V> = hashbrown::HashMap<K, V, BuildHasher>;
+
+#[cfg(all(not(feature = "small-buffer-opt"), feature = "std"))]
+type BufferVec<T> = Vec<T>;
+#[cfg(all(not(feature = "small-buffer-opt"), not(feature = "std")))]
+type BufferVec<T> = alloc::vec::Vec<T>;
+#[cfg(feature = "small-buffer-opt")]
+type BufferVec<T> = smallvec::SmallVec<[T; 1]>;

src/shape.rs

@@ -13,8 +13,8 @@ use unicode_segmentation::UnicodeSegmentation;
 
 use crate::fallback::FontFallbackIter;
 use crate::{
-    math, Align, AttrsList, CacheKeyFlags, Color, Font, FontSystem, LayoutGlyph, LayoutLine,
-    Metrics, ShapePlanCache, Wrap,
+    math, Align, AttrsList, BufferVec, CacheKeyFlags, Color, Font, FontSystem, LayoutGlyph,
+    LayoutLine, Metrics, ShapePlanCache, Wrap,
 };
 
 /// The shaping strategy of some text.
@@ -661,7 +661,7 @@ impl ShapeWord {
 #[derive(Clone, Debug)]
 pub struct ShapeSpan {
     pub level: unicode_bidi::Level,
-    pub words: Vec<ShapeWord>,
+    pub words: BufferVec<ShapeWord>,
 }
 
 impl ShapeSpan {
@@ -671,7 +671,7 @@ impl ShapeSpan {
     pub(crate) fn empty() -> Self {
         Self {
             level: unicode_bidi::Level::ltr(),
-            words: Vec::default(),
+            words: BufferVec::default(),
         }
     }
 
@@ -726,7 +726,7 @@ impl ShapeSpan {
         cached_words.clear();
         if line_rtl != level.is_rtl() {
             // Un-reverse previous words so the internal glyph counts match accurately when rewriting memory.
-            cached_words.append(&mut words);
+            cached_words.extend(words.drain(..));
         } else {
             cached_words.extend(words.drain(..).rev());
         }
@@ -802,7 +802,7 @@ impl ShapeSpan {
 #[derive(Clone, Debug)]
 pub struct ShapeLine {
     pub rtl: bool,
-    pub spans: Vec<ShapeSpan>,
+    pub spans: BufferVec<ShapeSpan>,
     pub metrics_opt: Option<Metrics>,
 }
 
@@ -831,7 +831,7 @@ impl ShapeLine {
     pub(crate) fn empty() -> Self {
         Self {
             rtl: false,
-            spans: Vec::default(),
+            spans: BufferVec::default(),
             metrics_opt: None,
         }
     }
@@ -1082,8 +1082,8 @@ impl ShapeLine {
         wrap: Wrap,
         align: Option<Align>,
         match_mono_width: Option<f32>,
-    ) -> Vec<LayoutLine> {
-        let mut lines = Vec::with_capacity(1);
+    ) -> BufferVec<LayoutLine> {
+        let mut lines = BufferVec::with_capacity(1);
         self.layout_to_buffer(
             &mut ShapeBuffer::default(),
             font_size,
@@ -1103,7 +1103,7 @@ impl ShapeLine {
         width_opt: Option<f32>,
         wrap: Wrap,
         align: Option<Align>,
-        layout_lines: &mut Vec<LayoutLine>,
+        layout_lines: &mut BufferVec<LayoutLine>,
         match_mono_width: Option<f32>,
     ) {
         // For each visual line a list of  (span index,  and range of words in that span)