Make the font atlas use a color image

crates/egui-wgpu/src/renderer.rs

@@ -564,19 +564,6 @@ impl Renderer {
                 );
                 Cow::Borrowed(&image.pixels)
             }
-            epaint::ImageData::Font(image) => {
-                assert_eq!(
-                    width as usize * height as usize,
-                    image.pixels.len(),
-                    "Mismatch between texture size and texel count"
-                );
-                profiling::scope!("font -> sRGBA");
-                Cow::Owned(
-                    image
-                        .srgba_pixels(Default::default())
-                        .collect::<Vec<epaint::Color32>>(),
-                )
-            }
         };
         let data_bytes: &[u8] = bytemuck::cast_slice(data_color32.as_slice());
 

crates/egui/src/context.rs

@@ -78,7 +78,7 @@ impl Default for WrappedTextureManager {
         // Will be filled in later
         let font_id = tex_mngr.alloc(
             "egui_font_texture".into(),
-            epaint::FontImage::new([0, 0]).into(),
+            epaint::ColorImage::filled([0, 0], Color32::TRANSPARENT).into(),
             Default::default(),
         );
         assert_eq!(
@@ -610,6 +610,8 @@ impl ContextImpl {
             log::trace!("Adding new fonts");
         }
 
+        let text_alpha_from_coverage = self.memory.options.style().visuals.text_alpha_from_coverage;
+
         let mut is_new = false;
 
         let fonts = self
@@ -624,13 +626,14 @@ impl ContextImpl {
                 Fonts::new(
                     pixels_per_point,
                     max_texture_side,
+                    text_alpha_from_coverage,
                     self.font_definitions.clone(),
                 )
             });
 
         {
             profiling::scope!("Fonts::begin_pass");
-            fonts.begin_pass(pixels_per_point, max_texture_side);
+            fonts.begin_pass(pixels_per_point, max_texture_side, text_alpha_from_coverage);
         }
 
         if is_new && self.memory.options.preload_font_glyphs {
@@ -1921,16 +1924,6 @@ impl Context {
         }
     }
 
-    pub(crate) fn reset_font_atlas(&self) {
-        let pixels_per_point = self.pixels_per_point();
-        let fonts = self.read(|ctx| {
-            ctx.fonts
-                .get(&pixels_per_point.into())
-                .map(|current_fonts| current_fonts.lock().fonts.definitions().clone())
-        });
-        self.memory_mut(|mem| mem.new_font_definitions = fonts);
-    }
-
     /// Tell `egui` which fonts to use.
     ///
     /// The default `egui` fonts only support latin and cyrillic alphabets,
@@ -2066,19 +2059,10 @@ impl Context {
     /// You can use [`Ui::style_mut`] to change the style of a single [`Ui`].
     pub fn set_style_of(&self, theme: Theme, style: impl Into<Arc<Style>>) {
         let style = style.into();
-        let mut recreate_font_atlas = false;
-        self.options_mut(|opt| {
-            let dest = match theme {
-                Theme::Dark => &mut opt.dark_style,
-                Theme::Light => &mut opt.light_style,
-            };
-            recreate_font_atlas =
-                dest.visuals.text_alpha_from_coverage != style.visuals.text_alpha_from_coverage;
-            *dest = style;
+        self.options_mut(|opt| match theme {
+            Theme::Dark => opt.dark_style = style,
+            Theme::Light => opt.light_style = style,
         });
-        if recreate_font_atlas {
-            self.reset_font_atlas();
-        }
     }
 
     /// The [`crate::Visuals`] used by all subsequent windows, panels etc.
@@ -2475,28 +2459,7 @@ impl ContextImpl {
         }
 
         // Inform the backend of all textures that have been updated (including font atlas).
-        let textures_delta = {
-            // HACK to get much nicer looking text in light mode.
-            // This assumes all text is black-on-white in light mode,
-            // and white-on-black in dark mode, which is not necessarily true,
-            // but often close enough.
-            // Of course this fails for cases when there is black-on-white text in dark mode,
-            // and white-on-black text in light mode.
-
-            let text_alpha_from_coverage =
-                self.memory.options.style().visuals.text_alpha_from_coverage;
-
-            let mut textures_delta = self.tex_manager.0.write().take_delta();
-
-            for (_, delta) in &mut textures_delta.set {
-                if let ImageData::Font(font) = &mut delta.image {
-                    delta.image =
-                        ImageData::Color(font.to_color_image(text_alpha_from_coverage).into());
-                }
-            }
-
-            textures_delta
-        };
+        let textures_delta = self.tex_manager.0.write().take_delta();
 
         let mut platform_output: PlatformOutput = std::mem::take(&mut viewport.output);
 
@@ -3094,17 +3057,9 @@ impl Context {
 
         options.ui(ui);
 
-        let text_alpha_from_coverage_changed =
-            prev_options.style().visuals.text_alpha_from_coverage
-                != options.style().visuals.text_alpha_from_coverage;
-
         if options != prev_options {
             self.options_mut(move |o| *o = options);
         }
-
-        if text_alpha_from_coverage_changed {
-            ui.ctx().reset_font_atlas();
-        }
     }
 
     fn fonts_tweak_ui(&self, ui: &mut Ui) {

crates/egui/src/lib.rs

@@ -467,7 +467,7 @@ pub use emath::{
     remap_clamp, vec2,
 };
 pub use epaint::{
-    ClippedPrimitive, ColorImage, CornerRadius, FontImage, ImageData, Margin, Mesh, PaintCallback,
+    ClippedPrimitive, ColorImage, CornerRadius, ImageData, Margin, Mesh, PaintCallback,
     PaintCallbackInfo, Shadow, Shape, Stroke, StrokeKind, TextureHandle, TextureId, mutex,
     text::{FontData, FontDefinitions, FontFamily, FontId, FontTweak},
     textures::{TextureFilter, TextureOptions, TextureWrapMode, TexturesDelta},

crates/egui_demo_lib/benches/benchmark.rs

@@ -168,6 +168,7 @@ pub fn criterion_benchmark(c: &mut Criterion) {
         let fonts = egui::epaint::text::Fonts::new(
             pixels_per_point,
             max_texture_side,
+            egui::epaint::AlphaFromCoverage::default(),
             egui::FontDefinitions::default(),
         );
         {
@@ -210,7 +211,11 @@ pub fn criterion_benchmark(c: &mut Criterion) {
 
             let mut rng = rand::rng();
             b.iter(|| {
-                fonts.begin_pass(pixels_per_point, max_texture_side);
+                fonts.begin_pass(
+                    pixels_per_point,
+                    max_texture_side,
+                    egui::epaint::AlphaFromCoverage::default(),
+                );
 
                 // Delete a random character, simulating a user making an edit in a long file:
                 let mut new_string = string.clone();

crates/egui_glow/src/painter.rs

@@ -534,23 +534,6 @@ impl Painter {
 
                 self.upload_texture_srgb(delta.pos, image.size, delta.options, data);
             }
-            egui::ImageData::Font(image) => {
-                assert_eq!(
-                    image.width() * image.height(),
-                    image.pixels.len(),
-                    "Mismatch between texture size and texel count"
-                );
-
-                let data: Vec<u8> = {
-                    profiling::scope!("font -> sRGBA");
-                    image
-                        .srgba_pixels(Default::default())
-                        .flat_map(|a| a.to_array())
-                        .collect()
-                };
-
-                self.upload_texture_srgb(delta.pos, image.size, delta.options, &data);
-            }
         };
     }
 

crates/epaint/benches/benchmark.rs

@@ -1,8 +1,8 @@
 use criterion::{Criterion, black_box, criterion_group, criterion_main};
 
 use epaint::{
-    ClippedShape, Color32, Mesh, PathStroke, Pos2, Rect, Shape, Stroke, TessellationOptions,
-    Tessellator, TextureAtlas, Vec2, pos2, tessellator::Path,
+    AlphaFromCoverage, ClippedShape, Color32, Mesh, PathStroke, Pos2, Rect, Shape, Stroke,
+    TessellationOptions, Tessellator, TextureAtlas, Vec2, pos2, tessellator::Path,
 };
 
 #[global_allocator]
@@ -66,7 +66,7 @@ fn tessellate_circles(c: &mut Criterion) {
         let pixels_per_point = 2.0;
         let options = TessellationOptions::default();
 
-        let atlas = TextureAtlas::new([4096, 256]);
+        let atlas = TextureAtlas::new([4096, 256], AlphaFromCoverage::default());
         let font_tex_size = atlas.size();
         let prepared_discs = atlas.prepared_discs();