All window events work!

src/platform_impl/macos/app.rs

@@ -0,0 +1,46 @@
+use cocoa::{appkit, base::id};
+use objc::{declare::ClassDecl, runtime::{Class, Object, Sel}};
+
+use platform_impl::platform::util;
+
+pub struct AppClass(pub *const Class);
+unsafe impl Send for AppClass {}
+unsafe impl Sync for AppClass {}
+
+lazy_static! {
+    pub static ref APP_CLASS: AppClass = unsafe {
+        let superclass = class!(NSApplication);
+        let mut decl = ClassDecl::new("WinitApp", superclass).unwrap();
+
+        decl.add_method(
+            sel!(sendEvent:),
+            send_event as extern fn(&Object, Sel, id),
+        );
+
+        AppClass(decl.register())
+    };
+}
+
+// Normally, holding Cmd + any key never sends us a `keyUp` event for that key.
+// Overriding `sendEvent:` like this fixes that. (https://stackoverflow.com/a/15294196)
+// Fun fact: Firefox still has this bug! (https://bugzilla.mozilla.org/show_bug.cgi?id=1299553)
+extern fn send_event(this: &Object, _sel: Sel, event: id) {
+    unsafe {
+        use self::appkit::NSEvent;
+        // For posterity, there are some undocumented event types
+        // (https://github.com/servo/cocoa-rs/issues/155)
+        // but that doesn't really matter here.
+        let event_type = event.eventType();
+        let modifier_flags = event.modifierFlags();
+        if event_type == appkit::NSKeyUp && util::has_flag(
+            modifier_flags,
+            appkit::NSEventModifierFlags::NSCommandKeyMask,
+        ) {
+            let key_window: id = msg_send![this, keyWindow];
+            let _: () = msg_send![key_window, sendEvent:event];
+        } else {
+            let superclass = util::superclass(this);
+            let _: () = msg_send![super(this, superclass), sendEvent:event];
+        }
+    }
+}