macOS: Avoid redundant initial resize event (#3913)

The `NSViewFrameDidChangeNotification` that we listen to is emitted when
`-[NSWindow setContentView]` is called, since that sets the frame of the
view as well.

So now we register the notification later, so that it's not triggered at
window creation.

This behaviour is well described in the documentation:
https://developer.apple.com/documentation/appkit/nsview/postsframechangednotifications?language=objc

src/changelog/unreleased.md

@@ -211,3 +211,4 @@ changelog entry.
 - On iOS, fixed `SurfaceResized` and `Window::surface_size` not reporting the size of the actual surface.
 - On macOS, fixed the scancode conversion for audio volume keys.
 - On macOS, fixed the scancode conversion for `IntlBackslash`.
+- On macOS, fixed redundant `SurfaceResized` event at window creation.

src/platform_impl/apple/appkit/view.rs

@@ -4,17 +4,17 @@ use std::collections::{HashMap, VecDeque};
 use std::ptr;
 use std::rc::Rc;
 
-use objc2::rc::{Retained, WeakId};
+use objc2::rc::Retained;
 use objc2::runtime::{AnyObject, Sel};
-use objc2::{declare_class, msg_send_id, mutability, sel, ClassType, DeclaredClass};
+use objc2::{declare_class, msg_send_id, mutability, ClassType, DeclaredClass};
 use objc2_app_kit::{
     NSApplication, NSCursor, NSEvent, NSEventPhase, NSResponder, NSTextInputClient,
-    NSTrackingRectTag, NSView, NSViewFrameDidChangeNotification,
+    NSTrackingRectTag, NSView,
 };
 use objc2_foundation::{
     MainThreadMarker, NSArray, NSAttributedString, NSAttributedStringKey, NSCopying,
-    NSMutableAttributedString, NSNotFound, NSNotificationCenter, NSObject, NSObjectProtocol,
-    NSPoint, NSRange, NSRect, NSSize, NSString, NSUInteger,
+    NSMutableAttributedString, NSNotFound, NSObject, NSObjectProtocol, NSPoint, NSRange, NSRect,
+    NSSize, NSString, NSUInteger,
 };
 
 use super::app_state::AppState;
@@ -134,9 +134,6 @@ pub struct ViewState {
     marked_text: RefCell<Retained<NSMutableAttributedString>>,
     accepts_first_mouse: bool,
 
-    // Weak reference because the window keeps a strong reference to the view
-    _ns_window: WeakId<WinitWindow>,
-
     /// The state of the `Option` as `Alt`.
     option_as_alt: Cell<OptionAsAlt>,
 }
@@ -177,9 +174,10 @@ declare_class!(
             self.ivars().tracking_rect.set(Some(tracking_rect));
         }
 
-        #[method(frameDidChange:)]
-        fn frame_did_change(&self, _event: &NSEvent) {
-            trace_scope!("frameDidChange:");
+        // Not a normal method on `NSView`, it's triggered by `NSViewFrameDidChangeNotification`.
+        #[method(viewFrameDidChangeNotification:)]
+        fn frame_did_change(&self, _notification: Option<&AnyObject>) {
+            trace_scope!("NSViewFrameDidChangeNotification");
             if let Some(tracking_rect) = self.ivars().tracking_rect.take() {
                 self.removeTrackingRect(tracking_rect);
             }
@@ -203,10 +201,7 @@ declare_class!(
         fn draw_rect(&self, _rect: NSRect) {
             trace_scope!("drawRect:");
 
-            // It's a workaround for https://github.com/rust-windowing/winit/issues/2640, don't replace with `self.window_id()`.
-            if let Some(window) = self.ivars()._ns_window.load() {
-                self.ivars().app_state.handle_redraw(window.id());
-            }
+            self.ivars().app_state.handle_redraw(self.window().id());
 
             // This is a direct subclass of NSView, no need to call superclass' drawRect:
         }
@@ -806,11 +801,10 @@ declare_class!(
 impl WinitView {
     pub(super) fn new(
         app_state: &Rc<AppState>,
-        window: &WinitWindow,
         accepts_first_mouse: bool,
         option_as_alt: OptionAsAlt,
+        mtm: MainThreadMarker,
     ) -> Retained<Self> {
-        let mtm = MainThreadMarker::from(window);
         let this = mtm.alloc().set_ivars(ViewState {
             app_state: Rc::clone(app_state),
             cursor_state: Default::default(),
@@ -825,34 +819,24 @@ impl WinitView {
             forward_key_to_app: Default::default(),
             marked_text: Default::default(),
             accepts_first_mouse,
-            _ns_window: WeakId::new(&window.retain()),
             option_as_alt: Cell::new(option_as_alt),
         });
         let this: Retained<Self> = unsafe { msg_send_id![super(this), init] };
 
-        this.setPostsFrameChangedNotifications(true);
-        let notification_center = unsafe { NSNotificationCenter::defaultCenter() };
-        unsafe {
-            notification_center.addObserver_selector_name_object(
-                &this,
-                sel!(frameDidChange:),
-                Some(NSViewFrameDidChangeNotification),
-                Some(&this),
-            )
-        }
-
         *this.ivars().input_source.borrow_mut() = this.current_input_source();
 
         this
     }
 
     fn window(&self) -> Retained<WinitWindow> {
-        // TODO: Simply use `window` property on `NSView`.
-        // That only returns a window _after_ the view has been attached though!
-        // (which is incompatible with `frameDidChange:`)
-        //
-        // unsafe { msg_send_id![self, window] }
-        self.ivars()._ns_window.load().expect("view to have a window")
+        let window = (**self).window().expect("view must be installed in a window");
+
+        if !window.isKindOfClass(WinitWindow::class()) {
+            unreachable!("view installed in non-WinitWindow");
+        }
+
+        // SAFETY: Just checked that the window is `WinitWindow`
+        unsafe { Retained::cast(window) }
     }
 
     fn queue_event(&self, event: WindowEvent) {

src/platform_impl/apple/appkit/window_delegate.rs

@@ -15,15 +15,15 @@ use objc2_app_kit::{
     NSAppKitVersionNumber, NSAppKitVersionNumber10_12, NSAppearance, NSAppearanceCustomization,
     NSAppearanceNameAqua, NSApplication, NSApplicationPresentationOptions, NSBackingStoreType,
     NSColor, NSDraggingDestination, NSFilenamesPboardType, NSPasteboard,
-    NSRequestUserAttentionType, NSScreen, NSToolbar, NSView, NSWindowButton, NSWindowDelegate,
-    NSWindowFullScreenButton, NSWindowLevel, NSWindowOcclusionState, NSWindowOrderingMode,
-    NSWindowSharingType, NSWindowStyleMask, NSWindowTabbingMode, NSWindowTitleVisibility,
-    NSWindowToolbarStyle,
+    NSRequestUserAttentionType, NSScreen, NSToolbar, NSView, NSViewFrameDidChangeNotification,
+    NSWindowButton, NSWindowDelegate, NSWindowFullScreenButton, NSWindowLevel,
+    NSWindowOcclusionState, NSWindowOrderingMode, NSWindowSharingType, NSWindowStyleMask,
+    NSWindowTabbingMode, NSWindowTitleVisibility, NSWindowToolbarStyle,
 };
 use objc2_foundation::{
     ns_string, CGFloat, MainThreadMarker, NSArray, NSCopying, NSDictionary, NSEdgeInsets,
     NSKeyValueChangeKey, NSKeyValueChangeNewKey, NSKeyValueChangeOldKey,
-    NSKeyValueObservingOptions, NSObject, NSObjectNSDelayedPerforming,
+    NSKeyValueObservingOptions, NSNotificationCenter, NSObject, NSObjectNSDelayedPerforming,
     NSObjectNSKeyValueObserverRegistration, NSObjectProtocol, NSPoint, NSRect, NSSize, NSString,
 };
 use tracing::{trace, warn};
@@ -170,7 +170,7 @@ declare_class!(
         #[method(windowDidResize:)]
         fn window_did_resize(&self, _: Option<&AnyObject>) {
             trace_scope!("windowDidResize:");
-            // NOTE: WindowEvent::SurfaceResized is reported in frameDidChange.
+            // NOTE: WindowEvent::SurfaceResized is reported using NSViewFrameDidChangeNotification.
             self.emit_move_event();
         }
 
@@ -658,9 +658,9 @@ fn new_window(
 
         let view = WinitView::new(
             app_state,
-            &window,
             attrs.platform_specific.accepts_first_mouse,
             attrs.platform_specific.option_as_alt,
+            mtm,
         );
 
         // The default value of `setWantsBestResolutionOpenGLSurface:` was `false` until
@@ -682,6 +682,23 @@ fn new_window(
         window.setContentView(Some(&view));
         window.setInitialFirstResponder(Some(&view));
 
+        // Configure the view to send notifications whenever its frame rectangle changes.
+        //
+        // We explicitly do this _after_ setting the view as the content view of the window, to
+        // avoid a resize event when creating the window.
+        view.setPostsFrameChangedNotifications(true);
+        // `setPostsFrameChangedNotifications` posts the notification immediately, so register the
+        // observer _after_, again so that the event isn't triggered initially.
+        let notification_center = unsafe { NSNotificationCenter::defaultCenter() };
+        unsafe {
+            notification_center.addObserver_selector_name_object(
+                &view,
+                sel!(viewFrameDidChangeNotification:),
+                Some(NSViewFrameDidChangeNotification),
+                Some(&view),
+            )
+        }
+
         if attrs.transparent {
             window.setOpaque(false);
             // See `set_transparent` for details on why we do this.