Pass around Arc<Galley> to avoid copying a lot of data

egui/src/containers/window.rs

@@ -673,7 +673,7 @@ fn paint_frame_interaction(
 struct TitleBar {
     id: Id,
     title_label: Label,
-    title_galley: Galley,
+    title_galley: std::sync::Arc<Galley>,
     min_rect: Rect,
     rect: Rect,
 }

egui/src/painter.rs

@@ -302,14 +302,14 @@ impl Painter {
     }
 
     /// Paint text that has already been layed out in a `Galley`.
-    pub fn galley(&self, pos: Pos2, galley: Galley, color: Color32) {
+    pub fn galley(&self, pos: Pos2, galley: std::sync::Arc<Galley>, color: Color32) {
         self.galley_with_italics(pos, galley, color, false)
     }
 
     pub fn galley_with_italics(
         &self,
         pos: Pos2,
-        galley: Galley,
+        galley: std::sync::Arc<Galley>,
         color: Color32,
         fake_italics: bool,
     ) {

egui/src/widgets/label.rs

@@ -1,5 +1,6 @@
 use crate::*;
 use epaint::Galley;
+use std::sync::Arc;
 
 /// Static text.
 ///
@@ -143,12 +144,12 @@ impl Label {
 }
 
 impl Label {
-    pub fn layout(&self, ui: &Ui) -> Galley {
+    pub fn layout(&self, ui: &Ui) -> Arc<Galley> {
         let max_width = ui.available_width();
         self.layout_width(ui, max_width)
     }
 
-    pub fn layout_width(&self, ui: &Ui, max_width: f32) -> Galley {
+    pub fn layout_width(&self, ui: &Ui, max_width: f32) -> Arc<Galley> {
         let text_style = self.text_style_or_default(ui.style());
         let wrap_width = if self.should_wrap(ui) {
             max_width
@@ -174,11 +175,11 @@ impl Label {
     // TODO: a paint method for painting anywhere in a ui.
     // This should be the easiest method of putting text anywhere.
 
-    pub fn paint_galley(&self, ui: &mut Ui, pos: Pos2, galley: Galley) {
+    pub fn paint_galley(&self, ui: &mut Ui, pos: Pos2, galley: Arc<Galley>) {
         self.paint_galley_focus(ui, pos, galley, false)
     }
 
-    fn paint_galley_focus(&self, ui: &mut Ui, pos: Pos2, galley: Galley, focus: bool) {
+    fn paint_galley_focus(&self, ui: &mut Ui, pos: Pos2, galley: Arc<Galley>, focus: bool) {
         let Self {
             mut background_color,
             code,
@@ -256,7 +257,12 @@ impl Label {
         })
     }
 
-    fn valign_galley(&self, ui: &Ui, text_style: TextStyle, mut galley: Galley) -> Galley {
+    fn valign_galley(
+        &self,
+        ui: &Ui,
+        text_style: TextStyle,
+        mut galley: Arc<Galley>,
+    ) -> Arc<Galley> {
         if text_style == TextStyle::Small {
             // Hacky McHackface strikes again:
             let dy = if self.raised {
@@ -269,8 +275,10 @@ impl Label {
                 // normal_text_heigth - font_height // align bottom
             };
 
-            for row in &mut galley.rows {
+            if dy != 0.0 {
-                row.translate_y(dy);
+                for row in &mut Arc::make_mut(&mut galley).rows {
+                    row.translate_y(dy);
+                }
             }
         }
         galley
@@ -293,12 +301,13 @@ impl Widget for Label {
             let first_row_indentation = max_width - ui.available_size_before_wrap().x;
 
             let text_style = self.text_style_or_default(ui.style());
-            let mut galley = ui.fonts().layout_multiline_with_indentation_and_max_width(
+            let galley = ui.fonts().layout_multiline_with_indentation_and_max_width(
                 text_style,
                 self.text.clone(),
                 first_row_indentation,
                 max_width,
             );
+            let mut galley: Galley = (*galley).clone();
 
             let pos = pos2(ui.max_rect().left(), ui.cursor().top());
 
@@ -321,7 +330,7 @@ impl Widget for Label {
                 }
             }
 
-            let galley = self.valign_galley(ui, text_style, galley);
+            let galley = self.valign_galley(ui, text_style, Arc::new(galley));
 
             let rect = galley.rows[0].rect().translate(vec2(pos.x, pos.y));
             let mut response = ui.allocate_rect(rect, sense);

egui_demo_lib/benches/benchmark.rs

@@ -75,9 +75,12 @@ pub fn criterion_benchmark(c: &mut Criterion) {
             egui::FontDefinitions::default(),
         );
         let font = &fonts[text_style];
-        c.bench_function("text layout", |b| {
+        c.bench_function("text layout (uncached)", |b| {
             b.iter(|| font.layout_multiline(LOREM_IPSUM_LONG.to_owned(), wrap_width))
         });
+        c.bench_function("text layout (cached)", |b| {
+            b.iter(|| fonts.layout_multiline(text_style, LOREM_IPSUM_LONG.to_owned(), wrap_width))
+        });
 
         let galley = font.layout_multiline(LOREM_IPSUM_LONG.to_owned(), wrap_width);
         let mut tessellator = egui::epaint::Tessellator::from_options(Default::default());

epaint/src/shape.rs

@@ -43,7 +43,7 @@ pub enum Shape {
         /// Top left corner of the first character..
         pos: Pos2,
         /// The layed out text.
-        galley: Galley,
+        galley: std::sync::Arc<Galley>,
         /// Text color (foreground).
         color: Color32,
         /// If true, tilt the letters for a hacky italics effect.

epaint/src/text/fonts.rs

@@ -278,7 +278,7 @@ impl Fonts {
 
     /// Always returns at least one row.
     /// Will line break at `\n`.
-    pub fn layout_no_wrap(&self, text_style: TextStyle, text: String) -> Galley {
+    pub fn layout_no_wrap(&self, text_style: TextStyle, text: String) -> Arc<Galley> {
         self.layout_multiline(text_style, text, f32::INFINITY)
     }
 
@@ -288,7 +288,7 @@ impl Fonts {
     ///
     /// Most often you probably want `\n` to produce a new row,
     /// and so [`Self::layout_no_wrap`] may be a better choice.
-    pub fn layout_single_line(&self, text_style: TextStyle, text: String) -> Galley {
+    pub fn layout_single_line(&self, text_style: TextStyle, text: String) -> Arc<Galley> {
         self.galley_cache.lock().layout(
             &self.fonts,
             LayoutJob {
@@ -306,7 +306,7 @@ impl Fonts {
         text_style: TextStyle,
         text: String,
         max_width_in_points: f32,
-    ) -> Galley {
+    ) -> Arc<Galley> {
         self.layout_multiline_with_indentation_and_max_width(
             text_style,
             text,
@@ -324,7 +324,7 @@ impl Fonts {
         text: String,
         first_row_indentation: f32,
         max_width_in_points: f32,
-    ) -> Galley {
+    ) -> Arc<Galley> {
         self.galley_cache.lock().layout(
             &self.fonts,
             LayoutJob {
@@ -377,7 +377,7 @@ struct LayoutJob {
 struct CachedGalley {
     /// When it was last used
     last_used: u32,
-    galley: Galley, // TODO: use an Arc instead!
+    galley: Arc<Galley>,
 }
 
 #[derive(Default)]
@@ -388,7 +388,7 @@ struct GalleyCache {
 }
 
 impl GalleyCache {
-    fn layout(&mut self, fonts: &BTreeMap<TextStyle, Font>, job: LayoutJob) -> Galley {
+    fn layout(&mut self, fonts: &BTreeMap<TextStyle, Font>, job: LayoutJob) -> Arc<Galley> {
         if let Some(cached) = self.cache.get_mut(&job) {
             cached.last_used = self.generation;
             cached.galley.clone()
@@ -410,6 +410,7 @@ impl GalleyCache {
                     max_width_in_points.into_inner(),
                 ),
             };
+            let galley = Arc::new(galley);
             self.cache.insert(
                 job,
                 CachedGalley {