Reduce the amount of FontDefinitions cloning

crates/egui/src/context.rs

@@ -401,7 +401,7 @@ struct ContextImpl {
     /// This is because the `Fonts` depend on `pixels_per_point` for the font atlas
     /// as well as kerning, font sizes, etc.
     fonts: std::collections::BTreeMap<OrderedFloat<f32>, Fonts>,
-    font_definitions: FontDefinitions,
+    font_definitions: Arc<FontDefinitions>,
 
     memory: Memory,
     animation_manager: AnimationManager,
@@ -583,22 +583,21 @@ impl ContextImpl {
         }
 
         if !self.memory.add_fonts.is_empty() {
+            // Recreate all the fonts
+            self.fonts.clear();
+            let mut font_definitions = self.font_definitions.as_ref().clone();
             let fonts = self.memory.add_fonts.drain(..);
             for font in fonts {
-                self.fonts.clear(); // recreate all the fonts
                 for family in font.families {
-                    let fam = self
-                        .font_definitions
-                        .families
-                        .entry(family.family)
-                        .or_default();
+                    let fam = font_definitions.families.entry(family.family).or_default();
                     match family.priority {
                         FontPriority::Highest => fam.insert(0, font.name.clone()),
                         FontPriority::Lowest => fam.push(font.name.clone()),
                     }
                 }
-                self.font_definitions.font_data.insert(font.name, font.data);
+                font_definitions.font_data.insert(font.name, font.data);
             }
+            self.font_definitions = Arc::new(font_definitions);
 
             #[cfg(feature = "log")]
             log::trace!("Adding new fonts");
@@ -1750,7 +1749,7 @@ impl Context {
     ///
     /// The new fonts will become active at the start of the next pass.
     /// This will overwrite the existing fonts.
-    pub fn set_fonts(&self, font_definitions: FontDefinitions) {
+    pub fn set_fonts(&self, font_definitions: Arc<FontDefinitions>) {
         crate::profile_function!();
 
         let pixels_per_point = self.pixels_per_point();
@@ -1760,7 +1759,7 @@ impl Context {
         self.read(|ctx| {
             if let Some(current_fonts) = ctx.fonts.get(&pixels_per_point.into()) {
                 // NOTE: this comparison is expensive since it checks TTF data for equality
-                if current_fonts.lock().fonts.definitions() == &font_definitions {
+                if current_fonts.lock().fonts.definitions() == font_definitions.as_ref() {
                     update_fonts = false; // no need to update
                 }
             }
@@ -2935,7 +2934,7 @@ impl Context {
     }
 
     fn fonts_tweak_ui(&self, ui: &mut Ui) {
-        let mut font_definitions = self.write(|ctx| ctx.font_definitions.clone());
+        let mut font_definitions = self.write(|ctx| ctx.font_definitions.as_ref().clone());
         let mut changed = false;
 
         for (name, data) in &mut font_definitions.font_data {
@@ -2947,7 +2946,7 @@ impl Context {
         }
 
         if changed {
-            self.set_fonts(font_definitions);
+            self.set_fonts(Arc::new(font_definitions));
         }
     }
 

crates/egui/src/lib.rs

@@ -667,7 +667,7 @@ pub enum WidgetType {
 /// For use in tests; especially doctests.
 pub fn __run_test_ctx(mut run_ui: impl FnMut(&Context)) {
     let ctx = Context::default();
-    ctx.set_fonts(FontDefinitions::empty()); // prevent fonts from being loaded (save CPU time)
+    ctx.set_fonts(Arc::new(FontDefinitions::empty())); // prevent fonts from being loaded (save CPU time)
     let _ = ctx.run(Default::default(), |ctx| {
         run_ui(ctx);
     });
@@ -676,7 +676,7 @@ pub fn __run_test_ctx(mut run_ui: impl FnMut(&Context)) {
 /// For use in tests; especially doctests.
 pub fn __run_test_ui(add_contents: impl Fn(&mut Ui)) {
     let ctx = Context::default();
-    ctx.set_fonts(FontDefinitions::empty()); // prevent fonts from being loaded (save CPU time)
+    ctx.set_fonts(Arc::new(FontDefinitions::empty())); // prevent fonts from being loaded (save CPU time)
     let _ = ctx.run(Default::default(), |ctx| {
         crate::CentralPanel::default().show(ctx, |ui| {
             add_contents(ui);

crates/egui/src/memory/mod.rs

@@ -77,7 +77,7 @@ pub struct Memory {
     // ------------------------------------------
     /// new fonts that will be applied at the start of the next frame
     #[cfg_attr(feature = "persistence", serde(skip))]
-    pub(crate) new_font_definitions: Option<epaint::text::FontDefinitions>,
+    pub(crate) new_font_definitions: Option<std::sync::Arc<epaint::text::FontDefinitions>>,
 
     /// add new font that will be applied at the start of the next frame
     #[cfg_attr(feature = "persistence", serde(skip))]

crates/egui_demo_lib/benches/benchmark.rs

@@ -90,11 +90,8 @@ pub fn criterion_benchmark(c: &mut Criterion) {
         let wrap_width = 512.0;
         let font_id = egui::FontId::default();
         let text_color = egui::Color32::WHITE;
-        let fonts = egui::epaint::text::Fonts::new(
-            pixels_per_point,
-            max_texture_side,
-            egui::FontDefinitions::default(),
-        );
+        let fonts =
+            egui::epaint::text::Fonts::new(pixels_per_point, max_texture_side, Default::default());
         {
             let mut locked_fonts = fonts.lock();
             c.bench_function("text_layout_uncached", |b| {

crates/epaint/src/text/fonts.rs

@@ -418,7 +418,7 @@ impl Fonts {
     pub fn new(
         pixels_per_point: f32,
         max_texture_side: usize,
-        definitions: FontDefinitions,
+        definitions: Arc<FontDefinitions>,
     ) -> Self {
         let fonts_and_cache = FontsAndCache {
             fonts: FontsImpl::new(pixels_per_point, max_texture_side, definitions),
@@ -614,7 +614,7 @@ impl FontsAndCache {
 pub struct FontsImpl {
     pixels_per_point: f32,
     max_texture_side: usize,
-    definitions: FontDefinitions,
+    definitions: Arc<FontDefinitions>,
     atlas: Arc<Mutex<TextureAtlas>>,
     font_impl_cache: FontImplCache,
     sized_family: ahash::HashMap<(OrderedFloat<f32>, FontFamily), Font>,
@@ -626,7 +626,7 @@ impl FontsImpl {
     pub fn new(
         pixels_per_point: f32,
         max_texture_side: usize,
-        definitions: FontDefinitions,
+        definitions: Arc<FontDefinitions>,
     ) -> Self {
         assert!(
             0.0 < pixels_per_point && pixels_per_point < 100.0,

crates/epaint/src/text/text_layout.rs

@@ -1042,7 +1042,7 @@ mod tests {
 
     #[test]
     fn test_zero_max_width() {
-        let mut fonts = FontsImpl::new(1.0, 1024, FontDefinitions::default());
+        let mut fonts = FontsImpl::new(1.0, 1024, Default::default());
         let mut layout_job = LayoutJob::single_section("W".into(), TextFormat::default());
         layout_job.wrap.max_width = 0.0;
         let galley = layout(&mut fonts, layout_job.into());
@@ -1053,7 +1053,7 @@ mod tests {
     fn test_truncate_with_newline() {
         // No matter where we wrap, we should be appending the newline character.
 
-        let mut fonts = FontsImpl::new(1.0, 1024, FontDefinitions::default());
+        let mut fonts = FontsImpl::new(1.0, 1024, Default::default());
         let text_format = TextFormat {
             font_id: FontId::monospace(12.0),
             ..Default::default()
@@ -1098,7 +1098,7 @@ mod tests {
 
     #[test]
     fn test_cjk() {
-        let mut fonts = FontsImpl::new(1.0, 1024, FontDefinitions::default());
+        let mut fonts = FontsImpl::new(1.0, 1024, Default::default());
         let mut layout_job = LayoutJob::single_section(
             "日本語とEnglishの混在した文章".into(),
             TextFormat::default(),
@@ -1113,7 +1113,7 @@ mod tests {
 
     #[test]
     fn test_pre_cjk() {
-        let mut fonts = FontsImpl::new(1.0, 1024, FontDefinitions::default());
+        let mut fonts = FontsImpl::new(1.0, 1024, Default::default());
         let mut layout_job = LayoutJob::single_section(
             "日本語とEnglishの混在した文章".into(),
             TextFormat::default(),
@@ -1128,7 +1128,7 @@ mod tests {
 
     #[test]
     fn test_truncate_width() {
-        let mut fonts = FontsImpl::new(1.0, 1024, FontDefinitions::default());
+        let mut fonts = FontsImpl::new(1.0, 1024, Default::default());
         let mut layout_job =
             LayoutJob::single_section("# DNA\nMore text".into(), TextFormat::default());
         layout_job.wrap.max_width = f32::INFINITY;

examples/custom_font/src/main.rs

@@ -5,6 +5,7 @@ use eframe::{
     egui,
     epaint::text::{FontInsert, InsertFontFamily},
 };
+use std::sync::Arc;
 
 fn main() -> eframe::Result {
     env_logger::init(); // Log to stderr (if you run with `RUST_LOG=debug`).
@@ -68,7 +69,7 @@ fn replace_fonts(ctx: &egui::Context) {
         .push("my_font".to_owned());
 
     // Tell egui to use these fonts:
-    ctx.set_fonts(fonts);
+    ctx.set_fonts(Arc::new(fonts));
 }
 
 struct MyApp {