App::clear_color: give egui::Visuals as argument

eframe/src/epi.rs

@@ -93,11 +93,13 @@ pub trait App {
 
     /// Background color for the app, e.g. what is sent to `gl.clearColor`.
     /// This is the background of your windows if you don't set a central panel.
-    fn clear_color(&self) -> egui::Rgba {
+    fn clear_color(&self, _visuals: &egui::Visuals) -> egui::Rgba {
         // NOTE: a bright gray makes the shadows of the windows look weird.
         // We use a bit of transparency so that if the user switches on the
         // `transparent()` option they get immediate results.
         egui::Color32::from_rgba_unmultiplied(12, 12, 12, 180).into()
+
+        // _visuals.window_fill() would also be a natural choice
     }
 
     /// Controls whether or not the native window position and size will be

eframe/src/native/run.rs

@@ -95,7 +95,11 @@ pub fn run(app_name: &str, native_options: &epi::NativeOptions, app_creator: epi
             crate::profile_scope!("frame");
             let screen_size_in_pixels: [u32; 2] = gl_window.window().inner_size().into();
 
-            egui_glow::painter::clear(&gl, screen_size_in_pixels, app.clear_color());
+            egui_glow::painter::clear(
+                &gl,
+                screen_size_in_pixels,
+                app.clear_color(&integration.egui_ctx.style().visuals),
+            );
 
             let egui::FullOutput {
                 platform_output,

eframe/src/web/backend.rs

@@ -278,7 +278,8 @@ impl AppRunner {
     }
 
     pub fn clear_color_buffer(&self) {
-        self.painter.clear(self.app.clear_color());
+        self.painter
+            .clear(self.app.clear_color(&self.egui_ctx.style().visuals));
     }
 
     /// Paint the results of the last call to [`Self::logic`].

egui_demo_app/src/wrap_app.rs

@@ -156,8 +156,8 @@ impl eframe::App for WrapApp {
         eframe::set_value(storage, eframe::APP_KEY, &self.state);
     }
 
-    fn clear_color(&self) -> egui::Rgba {
-        egui::Rgba::TRANSPARENT // we set a [`CentralPanel`] fill color in `demo_windows.rs`
+    fn clear_color(&self, visuals: &egui::Visuals) -> egui::Rgba {
+        visuals.window_fill().into()
     }
 
     fn update(&mut self, ctx: &egui::Context, frame: &mut eframe::Frame) {

examples/custom_window_frame/src/main.rs

@@ -24,7 +24,7 @@ fn main() {
 struct MyApp {}
 
 impl eframe::App for MyApp {
-    fn clear_color(&self) -> egui::Rgba {
+    fn clear_color(&self, _visuals: &egui::Visuals) -> egui::Rgba {
         egui::Rgba::TRANSPARENT // Make sure we don't paint anything behind the rounded corners
     }