perf: add buffer benchmarks (#1303)

benches/main.rs

@@ -1,6 +1,7 @@
 pub mod main {
     pub mod barchart;
     pub mod block;
+    pub mod buffer;
     pub mod line;
     pub mod list;
     pub mod paragraph;
@@ -12,6 +13,7 @@ pub use main::*;
 criterion::criterion_main!(
     barchart::benches,
     block::benches,
+    buffer::benches,
     line::benches,
     list::benches,
     paragraph::benches,

benches/main/buffer.rs

@@ -0,0 +1,65 @@
+use criterion::{black_box, BenchmarkId, Criterion};
+use ratatui::{
+    buffer::{Buffer, Cell},
+    layout::Rect,
+    text::Line,
+};
+
+criterion::criterion_group!(benches, empty, filled, with_lines);
+
+const fn rect(size: u16) -> Rect {
+    Rect {
+        x: 0,
+        y: 0,
+        width: size,
+        height: size,
+    }
+}
+
+fn empty(c: &mut Criterion) {
+    let mut group = c.benchmark_group("buffer/empty");
+    for size in [16, 64, 255] {
+        let area = rect(size);
+        group.bench_with_input(BenchmarkId::from_parameter(size), &area, |b, &area| {
+            b.iter(|| {
+                let _buffer = Buffer::empty(black_box(area));
+            });
+        });
+    }
+    group.finish();
+}
+
+/// This likely should have the same performance as `empty`, but it's here for completeness
+/// and to catch any potential performance regressions.
+fn filled(c: &mut Criterion) {
+    let mut group = c.benchmark_group("buffer/filled");
+    for size in [16, 64, 255] {
+        let area = rect(size);
+        let cell = Cell::new("AAAA"); // simulate a multi-byte character
+        group.bench_with_input(
+            BenchmarkId::from_parameter(size),
+            &(area, cell),
+            |b, (area, cell)| {
+                b.iter(|| {
+                    let _buffer = Buffer::filled(black_box(*area), cell.clone());
+                });
+            },
+        );
+    }
+    group.finish();
+}
+
+fn with_lines(c: &mut Criterion) {
+    let mut group = c.benchmark_group("buffer/with_lines");
+    for size in [16, 64, 255] {
+        let word_count = 50;
+        let lines = fakeit::words::sentence(word_count);
+        let lines = lines.lines().map(Line::from);
+        group.bench_with_input(BenchmarkId::from_parameter(size), &lines, |b, lines| {
+            b.iter(|| {
+                let _buffer = Buffer::with_lines(black_box(lines.clone()));
+            });
+        });
+    }
+    group.finish();
+}