Avoid unwraps in winit fullscreen handling code (#11735)

# Objective

- Get rid of unwraps in winit fullscreen handling code, which are the
source of some crashes.
- Fix #11275

## Solution

- Replace the unwraps with warnings. Ignore the fullscreen request, do
nothing instead.

crates/bevy_winit/src/system.rs

@@ -7,7 +7,9 @@ use bevy_ecs::{
     system::{NonSendMut, Query, SystemParamItem},
 };
 use bevy_utils::tracing::{error, info, warn};
-use bevy_window::{RawHandleWrapper, Window, WindowClosed, WindowCreated, WindowResized};
+use bevy_window::{
+    RawHandleWrapper, Window, WindowClosed, WindowCreated, WindowMode, WindowResized,
+};
 
 use raw_window_handle::{HasDisplayHandle, HasWindowHandle};
 use winit::{
@@ -119,35 +121,46 @@ pub(crate) fn changed_windows(
     mut window_resized: EventWriter<WindowResized>,
 ) {
     for (entity, mut window, mut cache) in &mut changed_windows {
-        if let Some(winit_window) = winit_windows.get_window(entity) {
+        let Some(winit_window) = winit_windows.get_window(entity) else {
+            continue;
+        };
+
         if window.title != cache.window.title {
             winit_window.set_title(window.title.as_str());
         }
 
         if window.mode != cache.window.mode {
             let new_mode = match window.mode {
-                    bevy_window::WindowMode::BorderlessFullscreen => {
+                WindowMode::BorderlessFullscreen => {
-                        Some(winit::window::Fullscreen::Borderless(None))
+                    Some(Some(winit::window::Fullscreen::Borderless(None)))
                 }
-                    bevy_window::WindowMode::Fullscreen => {
+                mode @ (WindowMode::Fullscreen | WindowMode::SizedFullscreen) => {
-                        Some(winit::window::Fullscreen::Exclusive(get_best_videomode(
+                    if let Some(current_monitor) = winit_window.current_monitor() {
-                            &winit_window.current_monitor().unwrap(),
+                        let videomode = match mode {
-                        )))
+                            WindowMode::Fullscreen => get_best_videomode(&current_monitor),
-                    }
+                            WindowMode::SizedFullscreen => get_fitting_videomode(
-                    bevy_window::WindowMode::SizedFullscreen => {
+                                &current_monitor,
-                        Some(winit::window::Fullscreen::Exclusive(get_fitting_videomode(
-                            &winit_window.current_monitor().unwrap(),
                                 window.width() as u32,
                                 window.height() as u32,
-                        )))
+                            ),
-                    }
+                            _ => unreachable!(),
-                    bevy_window::WindowMode::Windowed => None,
                         };
 
+                        Some(Some(winit::window::Fullscreen::Exclusive(videomode)))
+                    } else {
+                        warn!("Could not determine current monitor, ignoring exclusive fullscreen request for window {:?}", window.title);
+                        None
+                    }
+                }
+                WindowMode::Windowed => Some(None),
+            };
+
+            if let Some(new_mode) = new_mode {
                 if winit_window.fullscreen() != new_mode {
                     winit_window.set_fullscreen(new_mode);
                 }
             }
+        }
         if window.resolution != cache.window.resolution {
             let physical_size = PhysicalSize::new(
                 window.resolution.physical_width(),
@@ -261,9 +274,7 @@ pub(crate) fn changed_windows(
         // Currently unsupported changes
         if window.transparent != cache.window.transparent {
             window.transparent = cache.window.transparent;
-                warn!(
+            warn!("Winit does not currently support updating transparency after window creation.");
-                    "Winit does not currently support updating transparency after window creation."
-                );
         }
 
         #[cfg(target_arch = "wasm32")]
@@ -295,5 +306,4 @@ pub(crate) fn changed_windows(
 
         cache.window = window.clone();
     }
-    }
 }

crates/bevy_winit/src/winit_windows.rs

@@ -55,18 +55,25 @@ impl WinitWindows {
             WindowMode::BorderlessFullscreen => winit_window_builder.with_fullscreen(Some(
                 winit::window::Fullscreen::Borderless(event_loop.primary_monitor()),
             )),
-            WindowMode::Fullscreen => {
+            mode @ (WindowMode::Fullscreen | WindowMode::SizedFullscreen) => {
-                winit_window_builder.with_fullscreen(Some(winit::window::Fullscreen::Exclusive(
+                if let Some(primary_monitor) = event_loop.primary_monitor() {
-                    get_best_videomode(&event_loop.primary_monitor().unwrap()),
+                    let videomode = match mode {
-                )))
+                        WindowMode::Fullscreen => get_best_videomode(&primary_monitor),
-            }
+                        WindowMode::SizedFullscreen => get_fitting_videomode(
-            WindowMode::SizedFullscreen => winit_window_builder.with_fullscreen(Some(
+                            &primary_monitor,
-                winit::window::Fullscreen::Exclusive(get_fitting_videomode(
-                    &event_loop.primary_monitor().unwrap(),
                             window.width() as u32,
                             window.height() as u32,
-                )),
+                        ),
-            )),
+                        _ => unreachable!(),
+                    };
+
+                    winit_window_builder
+                        .with_fullscreen(Some(winit::window::Fullscreen::Exclusive(videomode)))
+                } else {
+                    warn!("Could not determine primary monitor, ignoring exclusive fullscreen request for window {:?}", window.title);
+                    winit_window_builder
+                }
+            }
             WindowMode::Windowed => {
                 if let Some(position) = winit_window_position(
                     &window.position,