Now if winit supports if the window cant be closed will not show the close button

crates/eframe/src/native/run.rs

@@ -5,8 +5,9 @@ use std::time::Instant;
 
 use egui::{epaint::ahash::HashMap, window::ViewportBuilder};
 use raw_window_handle::{HasRawDisplayHandle as _, HasRawWindowHandle as _};
-use winit::event_loop::{
+use winit::{
-    ControlFlow, EventLoop, EventLoopBuilder, EventLoopProxy, EventLoopWindowTarget,
+    event_loop::{ControlFlow, EventLoop, EventLoopBuilder, EventLoopProxy, EventLoopWindowTarget},
+    window::WindowButtons,
 };
 
 #[cfg(feature = "accesskit")]
@@ -1943,6 +1944,15 @@ fn create_winit_window_builder(builder: &ViewportBuilder) -> winit::window::Wind
                 .fullscreen
                 .then(|| winit::window::Fullscreen::Borderless(None)),
         )
+        .with_enabled_buttons(
+            WindowButtons::MAXIMIZE
+                | WindowButtons::MINIMIZE
+                | if builder.close_button {
+                    WindowButtons::CLOSE
+                } else {
+                    WindowButtons::empty()
+                },
+        )
         .with_active(builder.active);
     if let Some(inner_size) = builder.inner_size {
         window_builder = window_builder

crates/egui/src/containers/window.rs

@@ -26,6 +26,8 @@ pub struct ViewportBuilder {
     pub min_inner_size: Option<(u32, u32)>,
     pub max_inner_size: Option<(u32, u32)>,
     pub drag_and_drop: bool,
+
+    pub close_button: bool,
 }
 
 impl Default for ViewportBuilder {
@@ -49,6 +51,7 @@ impl Default for ViewportBuilder {
             min_inner_size: None,
             max_inner_size: None,
             drag_and_drop: true,
+            close_button: true,
         }
     }
 }
@@ -468,6 +471,7 @@ impl<'open> Window<'open> {
                 window_builder =
                     window_builder.with_inner_size((size.x as u32 + 1, size.y as u32 + 1));
             }
+            window_builder.close_button = open.is_some();
 
             let area_id = area.id;