Make Win32WindowHandle Send + Sync

Author: daxpedda

src/lib.rs

@@ -429,7 +429,7 @@ mod tests {
         assert_not_impl_any!(WaylandWindowHandle: Send, Sync);
         assert_impl_all!(DrmWindowHandle: Send, Sync);
         assert_not_impl_any!(GbmWindowHandle: Send, Sync);
-        assert_not_impl_any!(Win32WindowHandle: Send, Sync);
+        assert_impl_all!(Win32WindowHandle: Send, Sync);
         assert_not_impl_any!(WinRtWindowHandle: Send, Sync);
         assert_not_impl_any!(WebCanvasWindowHandle: Send, Sync);
         assert_not_impl_any!(WebOffscreenCanvasWindowHandle: Send, Sync);

src/windows.rs

@@ -55,13 +55,17 @@ pub struct Win32WindowHandle {
     pub hinstance: Option<NonNull<c_void>>,
 }
 
+unsafe impl Send for Win32WindowHandle {}
+unsafe impl Sync for Win32WindowHandle {}
+
 impl Win32WindowHandle {
     /// Create a new handle to a window.
     ///
     /// # Safety
     ///
-    /// It is assumed that the Win32 handle belongs to the current thread. This
-    /// is necessary for the handle to be considered "valid" in all cases.
+    /// Some APIs taking a `HWND` must observe its thread-affinity.
+    /// Consumers are responsible to ensure these safety guarantees themselves.
+    /// See [`GetWindowThreadProcessId()`](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getwindowthreadprocessid).
     ///
     /// # Example
     ///