feat: Event::Reopen support for macOS

CHANGELOG.md

@@ -72,6 +72,7 @@ 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

@@ -141,6 +141,7 @@ 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/reopen.rs

@@ -0,0 +1,61 @@
+#![allow(clippy::single_match)]
+
+use std::collections::HashMap;
+
+use simple_logger::SimpleLogger;
+use winit::{
+    event::{Event, WindowEvent},
+    event_loop::{EventLoop, EventLoopWindowTarget},
+    window::{Window, WindowId},
+};
+
+#[path = "util/fill.rs"]
+mod fill;
+
+fn new_window(event_loop: &EventLoopWindowTarget, windows: &mut HashMap<WindowId, Window>) {
+    let window = Window::new(event_loop).unwrap();
+    println!("Opened a new window: {:?}", window.id());
+    windows.insert(window.id(), window);
+}
+
+fn main() -> Result<(), impl std::error::Error> {
+    SimpleLogger::new().init().unwrap();
+    let event_loop = EventLoop::new().unwrap();
+
+    let mut windows = HashMap::new();
+    new_window(&event_loop, &mut windows);
+
+    event_loop.run(move |event, elwt| {
+        if let Event::WindowEvent { event, window_id } = event {
+            match event {
+                WindowEvent::CloseRequested => {
+                    println!("Window {window_id:?} has received the signal to close");
+
+                    // This drops the window, causing it to close.
+                    windows.remove(&window_id);
+
+                    // Keep the event loop running on macOS, even if all windows are closed.
+                    #[cfg(not(target_os = "macos"))]
+                    if windows.is_empty() {
+                        elwt.exit();
+                    }
+                }
+                WindowEvent::RedrawRequested => {
+                    if let Some(window) = windows.get(&window_id) {
+                        fill::fill_window(window);
+                    }
+                }
+                _ => (),
+            }
+        } else if let Event::Reopen {
+            has_visible_windows,
+        } = event
+        {
+            println!("Reopen event: has_visible_windows={}", has_visible_windows);
+            // If there are no visible windows, open a new one.
+            if !has_visible_windows {
+                new_window(elwt, &mut windows);
+            }
+        }
+    })
+}

src/event.rs

@@ -253,6 +253,25 @@ 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 typically called when the user clicks on the application's icon in the Dock.
+    /// The application should create a new window if it doesn't have any, or bring the
+    /// existing windows to the front. `has_visible_windows` is `true` if the application has
+    /// at least one visible window.
+    ///
+    /// [`applicationShouldHandleReopen`]: https://developer.apple.com/documentation/appkit/nsapplicationdelegate/1428638-applicationshouldhandlereopen
+    ///
+    /// ### Others
+    ///
+    /// - **Android / iOS / Web / Wayland / Windows / Orbital:** Unsupported.
+    Reopen { has_visible_windows: bool },
 }
 
 impl<T> Event<T> {
@@ -269,6 +288,11 @@ impl<T> Event<T> {
             Suspended => Ok(Suspended),
             Resumed => Ok(Resumed),
             MemoryWarning => Ok(MemoryWarning),
+            Reopen {
+                has_visible_windows,
+            } => Ok(Reopen {
+                has_visible_windows,
+            }),
         }
     }
 }

src/platform_impl/macos/app_delegate.rs

@@ -115,6 +115,16 @@ 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{ has_visible_windows });
+            // return true to preserve the default behavior, such as showing the minimized window.
+            true
+        }
+
     }
 );