feat: Event::Reopen support for macOS

CHANGELOG.md

@@ -78,6 +78,7 @@ Unreleased` header.
 - On Orbital, implement `set_window_level`.
 - On Orbital, emit `DeviceEvent::MouseMotion`.
 - On Wayland, fix title in CSD not updated from `AboutToWait`.
+- On macOS, emit `Event::Reopen` to handle dock icon click event.
 
 # 0.29.10
 

FEATURES.md

@@ -138,6 +138,7 @@ If your PR makes notable changes to Winit's features, please update this section
 * Full-size content view
 * Accepts first mouse
 * Set a preferred theme and get current theme.
+* Dock icon click event
 
 ### Unix
 * Window urgency

examples/window.rs

@@ -35,6 +35,10 @@ use winit::platform::startup_notify::{
 /// The amount of points to around the window for drag resize direction calculations.
 const BORDER_SIZE: f64 = 20.;
 
+/// Whether application should keep in the background even if all windows are closed.
+/// Default is `true` on macOS and `false` on other platforms.
+const KEEP_IN_BACKGROUND: bool = cfg!(macos_platform);
+
 fn main() -> Result<(), Box<dyn Error>> {
     let event_loop = EventLoop::<UserEvent>::with_user_event().build()?;
     let _event_loop_proxy = event_loop.create_proxy();
@@ -67,7 +71,7 @@ fn main() -> Result<(), Box<dyn Error>> {
             state.print_help();
         }
         Event::AboutToWait => {
-            if state.windows.is_empty() {
+            if state.windows.is_empty() && !KEEP_IN_BACKGROUND {
                 println!("No windows left, exiting...");
                 event_loop.exit();
             }
@@ -81,6 +85,15 @@ fn main() -> Result<(), Box<dyn Error>> {
         Event::UserEvent(event) => {
             println!("User event: {event:?}");
         }
+        Event::Reopen =>
+        {
+            #[cfg(macos_platform)]
+            if state.windows.is_empty() {
+                state
+                    .create_window(event_loop, None)
+                    .expect("failed to create window");
+            }
+        }
         Event::Suspended | Event::LoopExiting | Event::MemoryWarning => (),
     })?;
 

src/event.rs

@@ -253,6 +253,24 @@ pub enum Event<T: 'static> {
     ///
     /// - **macOS / Wayland / Windows / Orbital:** Unsupported.
     MemoryWarning,
+
+    /// Emitted when the application has received a reopen request from OS.
+    ///
+    /// ## Platform-specific
+    ///
+    /// ### macOS
+    ///
+    /// On macOS, the `Reopen` event is emitted in response to an [`applicationShouldHandleReopen`]
+    /// callback, which is usually called whenever the Finder reactivates an already running
+    /// application because the user double-clicked it again or used the dock to activate it.
+    /// Usually, the user would expect you to create a new window if there isn't any.
+    ///
+    /// [`applicationShouldHandleReopen`]: https://developer.apple.com/documentation/appkit/nsapplicationdelegate/1428638-applicationshouldhandlereopen
+    ///
+    /// ### Others
+    ///
+    /// - **Android / iOS / Web / Wayland / Windows / Orbital:** Unsupported.
+    Reopen,
 }
 
 impl<T> Event<T> {
@@ -269,6 +287,7 @@ impl<T> Event<T> {
             Suspended => Ok(Suspended),
             Resumed => Ok(Resumed),
             MemoryWarning => Ok(MemoryWarning),
+            Reopen => Ok(Reopen),
         }
     }
 }

src/platform_impl/macos/app_delegate.rs

@@ -113,6 +113,16 @@ declare_class!(
             // TODO: Notify every window that it will be destroyed, like done in iOS?
             self.internal_exit();
         }
+
+        #[method(applicationShouldHandleReopen:hasVisibleWindows:)]
+        fn should_handle_reopen(&self, _sender: &Option<&AnyObject>, _has_visible_windows: bool) -> bool {
+            trace_scope!("applicationShouldHandleReopen:hasVisibleWindows:");
+
+            self.handle_event(Event::Reopen);
+            // return true to preserve the default behavior, such as showing the minimized window.
+            true
+        }
+
     }
 );