From 1c415bd8fe109d2afba891b827e1bf99b3a2c997 Mon Sep 17 00:00:00 2001
From: Emil Ernerfeldt <emilernerfeldt@gmail.com>
Date: Mon, 8 Feb 2021 22:53:31 +0100
Subject: [PATCH] Add benchmark for text layout and tesselation

---
 egui_demo_lib/benches/benchmark.rs | 37 +++++++++++++++++++++++++++++-
 epaint/src/lib.rs                  |  2 +-
 epaint/src/mesh.rs                 |  7 ++++++
 epaint/src/text/font.rs            |  4 ++--
 4 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/egui_demo_lib/benches/benchmark.rs b/egui_demo_lib/benches/benchmark.rs
index 7a9f9844..72d77373 100644
--- a/egui_demo_lib/benches/benchmark.rs
+++ b/egui_demo_lib/benches/benchmark.rs
@@ -1,5 +1,7 @@
 use criterion::{criterion_group, criterion_main, Criterion};
 
+use egui_demo_lib::LOREM_IPSUM_LONG;
+
 pub fn criterion_benchmark(c: &mut Criterion) {
     let raw_input = egui::RawInput::default();
 
@@ -47,12 +49,45 @@ pub fn criterion_benchmark(c: &mut Criterion) {
         egui::CentralPanel::default().show(&ctx, |ui| {
             c.bench_function("label", |b| {
                 b.iter(|| {
-                    ui.label(egui_demo_lib::LOREM_IPSUM_LONG);
+                    ui.label(LOREM_IPSUM_LONG);
                 })
             });
         });
         let _ = ctx.end_frame();
     }
+
+    {
+        let pixels_per_point = 1.0;
+        let wrap_width = 512.0;
+        let text_style = egui::TextStyle::Body;
+        let fonts = egui::paint::text::Fonts::from_definitions(
+            pixels_per_point,
+            egui::FontDefinitions::default(),
+        );
+        let font = &fonts[text_style];
+        c.bench_function("text layout", |b| {
+            b.iter(|| font.layout_multiline(LOREM_IPSUM_LONG.to_owned(), wrap_width))
+        });
+
+        let galley = font.layout_multiline(LOREM_IPSUM_LONG.to_owned(), wrap_width);
+        let mut tesselator = egui::paint::Tessellator::from_options(Default::default());
+        let mut mesh = egui::paint::Mesh::default();
+        c.bench_function("tesselate text", |b| {
+            b.iter(|| {
+                let fake_italics = false;
+                tesselator.tessellate_text(
+                    &fonts,
+                    egui::Pos2::ZERO,
+                    &galley,
+                    text_style,
+                    egui::Color32::WHITE,
+                    fake_italics,
+                    &mut mesh,
+                );
+                mesh.clear();
+            })
+        });
+    }
 }
 
 criterion_group!(benches, criterion_benchmark);
diff --git a/epaint/src/lib.rs b/epaint/src/lib.rs
index ef7fb35b..4fb844fd 100644
--- a/epaint/src/lib.rs
+++ b/epaint/src/lib.rs
@@ -63,7 +63,7 @@ pub use {
     shape::Shape,
     stats::PaintStats,
     stroke::Stroke,
-    tessellator::TessellationOptions,
+    tessellator::{TessellationOptions, Tessellator},
     text::{Galley, TextStyle},
     texture_atlas::{Texture, TextureAtlas},
 };
diff --git a/epaint/src/mesh.rs b/epaint/src/mesh.rs
index c532556e..d9b2441e 100644
--- a/epaint/src/mesh.rs
+++ b/epaint/src/mesh.rs
@@ -45,6 +45,13 @@ impl Mesh {
         }
     }
 
+    /// Restore to default state, but without freeing memory.
+    pub fn clear(&mut self) {
+        self.indices.clear();
+        self.vertices.clear();
+        self.vertices = Default::default();
+    }
+
     pub fn bytes_used(&self) -> usize {
         std::mem::size_of::<Self>()
             + self.vertices.len() * std::mem::size_of::<Vertex>()
diff --git a/epaint/src/text/font.rs b/epaint/src/text/font.rs
index efc50bcc..2ec97543 100644
--- a/epaint/src/text/font.rs
+++ b/epaint/src/text/font.rs
@@ -218,8 +218,8 @@ impl Font {
     /// `\n` will (intentionally) show up as the replacement character.
     fn glyph_info(&self, c: char) -> (FontIndex, GlyphInfo) {
         {
-            if let Some(glyph_info) = self.glyph_info_cache.read().get(&c) {
-                return *glyph_info;
+            if let Some(font_index_glyph_info) = self.glyph_info_cache.read().get(&c) {
+                return *font_index_glyph_info;
             }
         }