Fix macOS memory leaks on dealloc of custom objects

src/platform_impl/macos/util/mod.rs

@@ -6,6 +6,7 @@ pub(crate) use self::r#async::*;
 
 use core_graphics::display::CGDisplay;
 use objc2::foundation::{CGFloat, NSNotFound, NSPoint, NSRange, NSRect, NSUInteger};
+use objc2::{msg_send, ClassType};
 
 use crate::dpi::LogicalPosition;
 
@@ -63,3 +64,30 @@ pub fn window_position(position: LogicalPosition<f64>) -> NSPoint {
         CGDisplay::main().pixels_high() as CGFloat - position.y as CGFloat,
     )
 }
+
+/// Helper for the broken `dealloc` impl of `declare_class!`
+#[derive(Debug)]
+pub(crate) struct DeallocHelper<T: ClassType>
+where
+    T::Super: ClassType,
+{
+    ptr: *const T,
+}
+
+impl<T: ClassType> DeallocHelper<T>
+where
+    T::Super: ClassType,
+{
+    pub(crate) unsafe fn new(ptr: *const T) -> Self {
+        Self { ptr }
+    }
+}
+
+impl<T: ClassType> Drop for DeallocHelper<T>
+where
+    T::Super: ClassType,
+{
+    fn drop(&mut self) {
+        unsafe { msg_send![super(self.ptr, T::Super::class()), dealloc] }
+    }
+}

src/platform_impl/macos/view.rs

@@ -140,6 +140,7 @@ declare_class!(
         pub(super) state: IvarDrop<Box<ViewState>>,
         marked_text: IvarDrop<Id<NSMutableAttributedString, Owned>>,
         accepts_first_mouse: bool,
+        _dealloc_helper: IvarDrop<Box<super::util::DeallocHelper<WinitView>>>,
     }
 
     unsafe impl ClassType for WinitView {
@@ -174,6 +175,8 @@ declare_class!(
                 Ivar::write(&mut this.state, Box::new(state));
                 Ivar::write(&mut this.marked_text, NSMutableAttributedString::new());
                 Ivar::write(&mut this.accepts_first_mouse, accepts_first_mouse);
+                let helper = unsafe { super::util::DeallocHelper::new(&*this) };
+                Ivar::write(&mut this._dealloc_helper, Box::new(helper));
 
                 this.setPostsFrameChangedNotifications(true);
 

src/platform_impl/macos/window.rs

@@ -113,6 +113,7 @@ declare_class!(
         // SAFETY: These are initialized in WinitWindow::new, right after it is created.
         shared_state: IvarDrop<Box<Mutex<SharedState>>>,
         decorations: IvarDrop<Box<AtomicBool>>,
+        _dealloc_helper: IvarDrop<Box<super::util::DeallocHelper<WinitWindow>>>,
     }
 
     unsafe impl ClassType for WinitWindow {
@@ -329,6 +330,8 @@ impl WinitWindow {
                     &mut this.decorations,
                     Box::new(AtomicBool::new(attrs.decorations)),
                 );
+                let helper = unsafe { super::util::DeallocHelper::new(&*this) };
+                Ivar::write(&mut this._dealloc_helper, Box::new(helper));
 
                 this.setReleasedWhenClosed(false);
                 this.setTitle(&NSString::from_str(&attrs.title));

src/platform_impl/macos/window_delegate.rs

@@ -42,6 +42,8 @@ declare_class!(
 
         // Used to prevent redundant events.
         previous_scale_factor: f64,
+
+        _dealloc_helper: IvarDrop<Box<super::util::DeallocHelper<WinitWindowDelegate>>>,
     }
 
     unsafe impl ClassType for WinitWindowDelegate {
@@ -63,6 +65,8 @@ declare_class!(
                 Ivar::write(&mut this.initial_fullscreen, initial_fullscreen);
                 Ivar::write(&mut this.previous_position, None);
                 Ivar::write(&mut this.previous_scale_factor, scale_factor);
+                let helper = unsafe { super::util::DeallocHelper::new(&*this) };
+                Ivar::write(&mut this._dealloc_helper, Box::new(helper));
 
                 if scale_factor != 1.0 {
                     this.queue_static_scale_factor_changed_event();