From 7c82d75896da97eef4255f2394818b27d47ec37f Mon Sep 17 00:00:00 2001
From: Adrien Prokopowicz <6529475+prokopyl@users.noreply.github.com>
Date: Mon, 10 Aug 2026 00:30:37 +0200
Subject: [PATCH 1/2] Make ParentWindowHandle Send+Sync on all platforms

---
 src/platform/macos/mod.rs    | 28 ++++++++++++++++++++++++----
 src/platform/macos/window.rs |  4 ++--
 src/settings.rs              |  6 ++++++
 3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/platform/macos/mod.rs b/src/platform/macos/mod.rs
index 156e7cfa..18d3b3e3 100644
--- a/src/platform/macos/mod.rs
+++ b/src/platform/macos/mod.rs
@@ -12,7 +12,7 @@ use dispatch2::MainThreadBound;
 pub use error::Error;
 use objc2::__framework_prelude::Retained;
 use objc2::rc::Weak;
-use objc2::MainThreadMarker;
+use objc2::{MainThreadMarker, MainThreadOnly};
 use objc2_app_kit::NSView;
 use raw_window_handle::{DisplayHandle, HasWindowHandle};
 use std::fmt;
@@ -69,9 +69,9 @@ impl fmt::Debug for PlatformHandle {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug)]
 pub struct ParentWindowHandle {
-    view: Retained<NSView>,
+    view: MainThreadBound<Retained<NSView>>,
 }
 
 impl ParentWindowHandle {
@@ -80,6 +80,26 @@ impl ParentWindowHandle {
     ) -> core::result::Result<Self, ParentWindowHandleError> {
         let view = extract_raw_window_handle(window.window_handle()?)?;
 
-        Ok(Self { view })
+        let mtm = view.mtm();
+        Ok(Self { view: MainThreadBound::new(view, mtm) })
     }
 }
+
+impl Clone for ParentWindowHandle {
+    fn clone(&self) -> Self {
+        // SAFETY: We only use Retained::clone, which is thread-safe
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+        let view = self.view.get(mtm);
+        Self { view: MainThreadBound::new(view.clone(), mtm) }
+    }
+}
+
+impl PartialEq for ParentWindowHandle {
+    fn eq(&self, other: &Self) -> bool {
+        // SAFETY: We only use Retained::eq, which is thread-safe
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+        Retained::eq(self.view.get(mtm), other.view.get(mtm))
+    }
+}
+
+impl Eq for ParentWindowHandle {}
diff --git a/src/platform/macos/window.rs b/src/platform/macos/window.rs
index 895352bc..808c8b43 100644
--- a/src/platform/macos/window.rs
+++ b/src/platform/macos/window.rs
@@ -39,7 +39,7 @@ impl WindowHandle {
             let _ = NSApplication::sharedApplication(mtm);
 
             if let Some(parent) = init.settings.parent.take() {
-                return Self::create_window_parented(init, parent.inner.view, mtm);
+                return Self::create_window_parented(init, parent.inner.view.into_inner(mtm), mtm);
             }
 
             Self::create_window_standalone(init, mtm)
@@ -126,7 +126,7 @@ impl WindowHandle {
         let Some(view) = self.view.load() else { return Ok(()) };
         let Some(view) = view.inner_ref() else { return Ok(()) };
 
-        BaseviewView::set_parent(view, new_parent.view);
+        BaseviewView::set_parent(view, new_parent.view.into_inner(view.mtm));
 
         Ok(())
     }
diff --git a/src/settings.rs b/src/settings.rs
index dd5fb2f4..22d51f3f 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -145,6 +145,12 @@ pub struct ParentWindowHandle {
     pub(crate) inner: platform::ParentWindowHandle,
 }
 
+// Assert this is Send+Sync
+const _: () = {
+    const fn foo<T: Send + Sync>() {}
+    foo::<ParentWindowHandle>();
+};
+
 impl ParentWindowHandle {
     /// Grabs a handle to the given `parent_window`, to later create a child window in it.
     pub fn from_window(parent_window: &impl HasWindowHandle) -> Self {

From bfe6723fac3237ff2dbab99b156f4de32d774eb3 Mon Sep 17 00:00:00 2001
From: Adrien Prokopowicz <6529475+prokopyl@users.noreply.github.com>
Date: Mon, 10 Aug 2026 00:41:43 +0200
Subject: [PATCH 2/2] Fix win build

---
 src/platform/win/mod.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/platform/win/mod.rs b/src/platform/win/mod.rs
index a295679e..9f650ef8 100644
--- a/src/platform/win/mod.rs
+++ b/src/platform/win/mod.rs
@@ -54,6 +54,11 @@ pub struct ParentWindowHandle {
     handle: HWnd,
 }
 
+// SAFETY: ParentWindowHandle does not actually expose any thread-unsafe operation
+unsafe impl Send for ParentWindowHandle {}
+// SAFETY: ParentWindowHandle does not actually expose any thread-unsafe operation
+unsafe impl Sync for ParentWindowHandle {}
+
 impl ParentWindowHandle {
     pub fn extract(
         parent: &impl HasWindowHandle,