Handle individual windows closing properly

Apply @bjorn3's suggestion

crates/bevy_window/Cargo.toml

@@ -14,6 +14,7 @@ keywords = ["bevy"]
 
 [dependencies]
 # bevy
+bevy_ecs = { path = "../bevy_ecs", version = "0.5.0" }
 bevy_app = { path = "../bevy_app", version = "0.5.0" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.5.0" }
 bevy_math = { path = "../bevy_math", version = "0.5.0" }

crates/bevy_window/src/event.rs

@@ -26,6 +26,9 @@ pub struct WindowCreated {
 
 /// An event that is sent whenever a close was requested for a window. For example: when the "close"
 /// button is pressed on a window.
+///
+/// By default, these events are handled by closing the corresponding [`crate::Window`].
+/// To disable this behaviour, set `close_when_requested` on the [`crate::WindowPlugin`] to `false`
 #[derive(Debug, Clone)]
 pub struct WindowCloseRequested {
     pub id: WindowId,
@@ -34,7 +37,10 @@ pub struct WindowCloseRequested {
 /// An event that is sent whenever a window is closed.
 /// This will only be sent in response to the [`Window::close`] method.
 ///
-/// [`Window::close`]: `crate::window::Window::close`
+/// By default, when no windows are open, the app will close.
+/// To disable this behaviour, set `exit_on_all_closed` on the [`crate::WindowPlugin`] to `false`
+///
+/// [`Window::close`]: `crate::Window::close`
 #[derive(Debug, Clone)]
 pub struct WindowClosed {
     pub id: WindowId,

crates/bevy_window/src/lib.rs

@@ -22,15 +22,20 @@ use bevy_app::{prelude::*, Events};
 use bevy_ecs::system::IntoSystem;
 
 pub struct WindowPlugin {
+    /// Whether to add a default window based on the [`WindowDescriptor`] resource
     pub add_primary_window: bool,
-    pub exit_on_close: bool,
+    /// Whether to close the app when there are no open windows
+    pub exit_on_all_closed: bool,
+    /// Whether to close windows when they are requested to be closed (i.e. when the close button is pressed)
+    pub close_when_requested: bool,
 }
 
 impl Default for WindowPlugin {
     fn default() -> Self {
         WindowPlugin {
             add_primary_window: true,
-            exit_on_close: true,
+            close_when_requested: true,
+            exit_on_all_closed: true,
         }
     }
 }
@@ -69,8 +74,11 @@ impl Plugin for WindowPlugin {
             });
         }
 
-        if self.exit_on_close {
-            app.add_system(exit_on_window_close_system.system());
+        if self.exit_on_all_closed {
+            app.add_system(exit_on_all_closed.system());
+        }
+        if self.close_when_requested {
+            app.add_system(close_when_requested.system());
         }
     }
 }

crates/bevy_window/src/system.rs

@@ -1,11 +1,18 @@
-use crate::WindowCloseRequested;
+use crate::{Window, WindowCloseRequested, Windows};
 use bevy_app::{AppExit, EventReader, EventWriter};
+use bevy_ecs::prelude::{Res, ResMut};
 
-pub fn exit_on_window_close_system(
-    mut app_exit_events: EventWriter<AppExit>,
-    mut window_close_requested_events: EventReader<WindowCloseRequested>,
-) {
-    if window_close_requested_events.iter().next().is_some() {
+pub fn exit_on_all_closed(mut app_exit_events: EventWriter<AppExit>, windows: Res<Windows>) {
+    if windows.iter().count() == 0 {
         app_exit_events.send(AppExit);
     }
 }
+
+pub fn close_when_requested(
+    mut windows: ResMut<Windows>,
+    mut closed: EventReader<WindowCloseRequested>,
+) {
+    for event in closed.iter() {
+        windows.get_mut(event.id).map(Window::close);
+    }
+}

crates/bevy_winit/src/lib.rs

@@ -170,7 +170,7 @@ fn change_window(world: &mut World) {
             }
         }
     }
-    if removed_windows.len() > 0 {
+    if !removed_windows.is_empty() {
         let mut events = world.get_resource_mut::<Events<WindowClosed>>().unwrap();
         for id in removed_windows {
             windows.remove(id);
@@ -280,16 +280,19 @@ pub fn winit_runner_with(mut app: App, mut event_loop: EventLoop<()>) {
                         window_id
                     } else {
                         warn!(
-                            "Skipped event for unknown winit Window Id {:?}",
-                            winit_window_id
+                            "Skipped event for unknown winit Window Id {:?}: {:?}",
+                            winit_window_id, event
                         );
                         return;
                     };
 
                 let window = if let Some(window) = windows.get_mut(window_id) {
                     window
                 } else {
-                    warn!("Skipped event for unknown Window Id {:?}", winit_window_id);
+                    warn!(
+                        "Skipped event for unknown Window Id {:?}: {:?}",
+                        winit_window_id, event
+                    );
                     return;
                 };