wayland: add WindowExtWayland::xdg_toplevel

Fixes #4068.

src/changelog/unreleased.md

@@ -44,6 +44,7 @@ changelog entry.
 
 - On Windows, add `IconExtWindows::from_resource_name`.
 - On Windows, add `CursorGrabMode::Locked`.
+- On Wayland, add `WindowExtWayland::xdg_toplevel`.
 
 ### Fixed
 

src/platform/wayland.rs

@@ -13,6 +13,10 @@
 //! * `wayland-csd-adwaita` (default).
 //! * `wayland-csd-adwaita-crossfont`.
 //! * `wayland-csd-adwaita-notitle`.
+
+use std::ffi::c_void;
+use std::ptr::NonNull;
+
 use crate::event_loop::{ActiveEventLoop, EventLoop, EventLoopBuilder};
 use crate::monitor::MonitorHandle;
 use crate::window::{Window, WindowAttributes};
@@ -72,9 +76,25 @@ impl<T> EventLoopBuilderExtWayland for EventLoopBuilder<T> {
 }
 
 /// Additional methods on [`Window`] that are specific to Wayland.
-pub trait WindowExtWayland {}
+///
+/// [`Window`]: crate::window::Window
+pub trait WindowExtWayland {
+    /// Returns `xdg_toplevel` of the window or [`None`] if the window is X11 window.
+    fn xdg_toplevel(&self) -> Option<NonNull<c_void>>;
+}
 
-impl WindowExtWayland for Window {}
+impl WindowExtWayland for Window {
+    #[inline]
+    fn xdg_toplevel(&self) -> Option<NonNull<c_void>> {
+        #[allow(clippy::single_match)]
+        match &self.window {
+            #[cfg(x11_platform)]
+            crate::platform_impl::Window::X(_) => None,
+            #[cfg(wayland_platform)]
+            crate::platform_impl::Window::Wayland(window) => window.xdg_toplevel(),
+        }
+    }
+}
 
 /// Additional methods on [`WindowAttributes`] that are specific to Wayland.
 pub trait WindowAttributesExtWayland {

src/platform_impl/linux/wayland/window/mod.rs

@@ -1,5 +1,7 @@
 //! The Wayland window.
 
+use std::ffi::c_void;
+use std::ptr::NonNull;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 
@@ -223,6 +225,10 @@ impl Window {
             window_events_sink,
         })
     }
+
+    pub(crate) fn xdg_toplevel(&self) -> Option<NonNull<c_void>> {
+        NonNull::new(self.window.xdg_toplevel().id().as_ptr().cast())
+    }
 }
 
 impl Window {