Trace sendEvent: calls in AppKit

Most events in AppKit go through `sendEvent:`, and they contain a lot of
information, so it's nice to surface this when debugging.

We could override `sendEvent:` in UIKit and track this in there too, but
that's much less important, since there the relevant events are fairly
narrowly scoped, see the link below, other events go through CFRunLoop.
https://developer.apple.com/documentation/uikit/uievent/eventtype

Author: madsmtm

winit-appkit/src/app.rs

@@ -1,14 +1,15 @@
 #![allow(clippy::unnecessary_cast)]
 
 use std::cell::Cell;
-use std::mem;
 use std::rc::Rc;
+use std::{mem, ptr};
 
 use dispatch2::MainThreadBound;
 use objc2::runtime::{Imp, Sel};
 use objc2::sel;
 use objc2_app_kit::{NSApplication, NSEvent, NSEventModifierFlags, NSEventType};
 use objc2_foundation::MainThreadMarker;
+use tracing::trace_span;
 use winit_core::event::{DeviceEvent, ElementState};
 
 use super::app_state::AppState;
@@ -21,6 +22,8 @@ static ORIGINAL: MainThreadBound<Cell<Option<SendEvent>>> = {
 };
 
 extern "C-unwind" fn send_event(app: &NSApplication, sel: Sel, event: &NSEvent) {
+    // Pass `RUST_LOG='trace,winit_appkit::app=off'` if you want TRACE logs but not this.
+    let _entered = trace_span!("sendEvent:", ?event).entered();
     let mtm = MainThreadMarker::from(app);
 
     // Normally, holding Cmd + any key never sends us a `keyUp` event for that key.
@@ -48,7 +51,7 @@ extern "C-unwind" fn send_event(app: &NSApplication, sel: Sel, event: &NSEvent)
     original(app, sel, event)
 }
 
-/// Override the [`sendEvent:`][NSApplication::sendEvent] method on the given application class.
+/// Intercept the [`sendEvent:`][NSApplication::sendEvent] method on the given application class.
 ///
 /// The previous implementation created a subclass of [`NSApplication`], however we would like to
 /// give the user full control over their `NSApplication`, so we override the method here using
@@ -75,9 +78,7 @@ pub(crate) fn override_send_event(global_app: &NSApplication) {
     let overridden = unsafe { mem::transmute::<SendEvent, Imp>(send_event) };
 
     // If we've already overridden the method, don't do anything.
-    // FIXME(madsmtm): Use `std::ptr::fn_addr_eq` (Rust 1.85) once available in MSRV.
-    #[allow(unknown_lints, unpredictable_function_pointer_comparisons)]
-    if overridden == method.implementation() {
+    if ptr::fn_addr_eq(overridden, method.implementation()) {
         return;
     }