Add button benchmark

crates/egui_demo_lib/README.md

@@ -14,3 +14,16 @@ The demo library is a separate crate for three reasons:
 * To remove the amount of code in `egui` proper.
 * To make it easy for 3rd party egui integrations to use it for tests.
   - See for instance https://github.com/not-fl3/egui-miniquad/blob/master/examples/demo.rs
+
+This crate also contains benchmarks for egui. 
+Run them with 
+```bash
+# Run all benchmarks
+cargo bench -p egui_demo_lib 
+
+# Run a single benchmark
+cargo bench -p egui_demo_lib "benchmark name"
+
+# Profile benchmarks with cargo-flamegraph (--root flag is necessary for MacOS)
+CARGO_PROFILE_BENCH_DEBUG=true cargo flamegraph --bench benchmark --root -p egui_demo_lib  -- --bench "benchmark name"
+```

crates/egui_demo_lib/benches/benchmark.rs

@@ -1,8 +1,10 @@
 use std::fmt::Write as _;
 
-use criterion::{criterion_group, criterion_main, Criterion};
+use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
 
 use egui::epaint::TextShape;
+use egui::load::SizedTexture;
+use egui::{Button, TextureId, UiBuilder, Vec2};
 use egui_demo_lib::LOREM_IPSUM_LONG;
 use rand::Rng as _;
 
@@ -57,14 +59,63 @@ pub fn criterion_benchmark(c: &mut Criterion) {
         let _ = ctx.run(RawInput::default(), |ctx| {
             egui::CentralPanel::default().show(ctx, |ui| {
                 c.bench_function("label &str", |b| {
-                    b.iter(|| {
-                        ui.label("the quick brown fox jumps over the lazy dog");
-                    });
+                    b.iter_batched_ref(
+                        || ui.new_child(UiBuilder::new()),
+                        |ui| {
+                            ui.label("the quick brown fox jumps over the lazy dog");
+                        },
+                        BatchSize::LargeInput,
+                    )
                 });
                 c.bench_function("label format!", |b| {
-                    b.iter(|| {
-                        ui.label("the quick brown fox jumps over the lazy dog".to_owned());
-                    });
+                    b.iter_batched_ref(
+                        || ui.new_child(UiBuilder::new()),
+                        |ui| {
+                            ui.label("the quick brown fox jumps over the lazy dog".to_owned());
+                        },
+                        BatchSize::LargeInput,
+                    )
+                });
+            });
+        });
+    }
+
+    {
+        let ctx = egui::Context::default();
+        let _ = ctx.run(RawInput::default(), |ctx| {
+            egui::CentralPanel::default().show(ctx, |ui| {
+                let mut group = c.benchmark_group("button");
+
+                // To ensure we have a valid image, let's use the font texture. The size
+                // shouldn't be important for this benchmark.
+                let image = SizedTexture::new(TextureId::default(), Vec2::splat(16.0));
+
+                group.bench_function("button", |b| {
+                    b.iter_batched_ref(
+                        || ui.new_child(UiBuilder::new()),
+                        |ui| {
+                            ui.add(Button::new("Hello World"));
+                        },
+                        BatchSize::LargeInput,
+                    );
+                });
+                group.bench_function("button image", |b| {
+                    b.iter_batched_ref(
+                        || ui.new_child(UiBuilder::new()),
+                        |ui| {
+                            ui.add(Button::image_and_text(image, "Hello World"));
+                        },
+                        BatchSize::LargeInput,
+                    )
+                });
+                group.bench_function("button image right text", |b| {
+                    b.iter_batched_ref(
+                        || ui.new_child(UiBuilder::new()),
+                        |ui| {
+                            ui.add(Button::image_and_text(image, "Hello World").right_text("⏵"));
+                        },
+                        BatchSize::LargeInput,
+                    )
                 });
             });
         });