Support an OpenURL event on macOS

This hookst log into the application:openUrls delegate callback on macOS to deliver
a corresponding `Event::OpenURL` to applications.

Although this event is currently only supported on macOS; potentially in the
future this could also be supported on Linux by handling the
org.freedesktop.Application.Open method and potentially Android Intent's with a
URL could be mapped to OpenURL events via some Activity::onNewIntent
integration.

Cargo.toml

@@ -105,6 +105,7 @@ features = [
     "Foundation_NSProcessInfo",
     "Foundation_NSThread",
     "Foundation_NSNumber",
+    "Foundation_NSURL",
 ]
 
 [target.'cfg(target_os = "ios")'.dependencies.icrate]

src/event.rs

@@ -65,6 +65,13 @@ pub enum Event<T: 'static> {
     /// [`ControlFlow::WaitUntil`](crate::event_loop::ControlFlow::WaitUntil) has elapsed.
     NewEvents(StartCause),
 
+    /// Emitted if a user has requested to open an application specific URL that is registered with the OS
+    ///
+    /// # Portability
+    ///
+    /// This event is only ever delivered on MacOS currently
+    OpenURL { url: String },
+
     /// Emitted when the OS sends an event to a winit window.
     WindowEvent {
         window_id: WindowId,
@@ -259,6 +266,7 @@ impl<T> Event<T> {
         use self::Event::*;
         match self {
             UserEvent(_) => Err(self),
+            OpenURL { url } => Ok(OpenURL { url }),
             WindowEvent { window_id, event } => Ok(WindowEvent { window_id, event }),
             DeviceEvent { device_id, event } => Ok(DeviceEvent { device_id, event }),
             NewEvents(cause) => Ok(NewEvents(cause)),

src/platform_impl/macos/app_delegate.rs

@@ -1,11 +1,13 @@
 use std::ptr::NonNull;
 
-use icrate::Foundation::NSObject;
+use icrate::Foundation::{NSArray, NSObject, NSURL};
 use objc2::declare::{IvarBool, IvarEncode};
 use objc2::rc::Id;
 use objc2::runtime::AnyObject;
 use objc2::{declare_class, msg_send, msg_send_id, mutability, ClassType};
 
+use crate::event::Event;
+
 use super::app_state::AppState;
 use super::appkit::NSApplicationActivationPolicy;
 
@@ -58,6 +60,17 @@ declare_class!(
             // TODO: Notify every window that it will be destroyed, like done in iOS?
             AppState::internal_exit();
         }
+
+        #[method(application:openURLs:)]
+        fn application_open_urls(&self, _application: &NSObject, urls: &NSArray<NSURL>) {
+            for url in urls {
+                if let Some(url) = unsafe { url.absoluteString() } {
+                    AppState::queue_event(Event::OpenURL {
+                        url: url.to_string(),
+                    });
+                }
+            }
+        }
     }
 );