Update example and now the viewport will always render if can create a native window will be embedded

crates/eframe/src/native/run.rs

@@ -1065,11 +1065,7 @@ mod glow_integration {
                         let screen_size_in_pixels: [u32; 2] =
                             win.window.as_ref().unwrap().inner_size().into();
 
-                        egui_glow::painter::clear(
+                        egui_glow::painter::clear(&gl, screen_size_in_pixels, [0.0, 0.0, 0.0, 0.0]);
-                            &gl,
-                            screen_size_in_pixels,
-                            app.clear_color(&integration.egui_ctx.style().visuals),
-                        );
 
                         integration.egui_ctx.set_current_viewport_id(win.window_id);
                         egui::FullOutput {

crates/egui/src/context.rs

@@ -1987,13 +1987,12 @@ impl Context {
         window_builder: ViewportBuilder,
         func: impl Fn(&Context, u64, u64) + Send + Sync + 'static,
     ) {
-        let id = self.write(|ctx| {
+        if self.is_desktop() {
-            if ctx.is_desktop {
+            self.write(|ctx| {
                 if let Some(window) = ctx.viewports.get_mut(&window_builder.title) {
                     window.2 = ctx.current_rendering_viewport;
                     window.3 = true;
                     window.4 = Arc::new(Box::new(func));
-                    window.1
                 } else {
                     let id = ctx.viewport_counter + 1;
                     ctx.viewport_counter = id;
@@ -2007,12 +2006,11 @@ impl Context {
                             Arc::new(Box::new(func)),
                         ),
                     );
-                    id
-                }
-            } else {
-                0
                 }
             });
+        } else {
+            func(self, 0, 0);
+        }
     }
 }
 

examples/hello_world_simple/src/main.rs

@@ -2,7 +2,7 @@
 
 use std::sync::{Arc, RwLock};
 
-use eframe::egui;
+use eframe::egui::{self, window::ViewportBuilder};
 
 fn main() -> Result<(), eframe::Error> {
     env_logger::init(); // Log to stderr (if you run with `RUST_LOG=debug`).
@@ -36,6 +36,34 @@ fn main() -> Result<(), eframe::Error> {
                 age += 1;
             }
             ui.label(format!("Hello '{name}', age {age}"));
+            let mut is_desktop = ctx.is_desktop();
+            ui.checkbox(&mut is_desktop, "Is Desktop");
+            ctx.set_desktop(is_desktop);
+
+            ctx.create_viewport(
+                ViewportBuilder::default()
+                    .with_inner_size((50, 30))
+                    .with_decorations(false)
+                    .with_transparent(true)
+                    .with_resizable(false),
+                |ctx, _, _| {
+                    let size = egui::Rect::from_min_size(
+                        egui::Pos2::new(0.0, 0.0),
+                        egui::Vec2::new(50.0, 50.0),
+                    );
+                    let mut ui = egui::Ui::new(
+                        ctx.clone(),
+                        egui::LayerId::background(),
+                        "Viewport Popup".into(),
+                        size,
+                        size,
+                    );
+                    egui::Frame::popup(&ctx.style()).show(&mut ui, |ui| {
+                        ui.label("Popup");
+                    });
+                },
+            );
+
             let clone = window1_embedded.clone();
             let embedded = *window1_embedded.read().unwrap();
             egui::CollapsingHeader::new("Show Test1").show(ui, |ui| {