wayland: add WindowExtWayland::xdg_toplevel

Fixes #4068.

src/changelog/unreleased.md

@@ -70,6 +70,7 @@ changelog entry.
 - Added `Window::surface_position`, which is the position of the surface inside the window.
 - Added `Window::safe_area`, which describes the area of the surface that is unobstructed.
 - On X11, Wayland, Windows and macOS, improved scancode conversions for more obscure key codes.
+- On Wayland, add `WindowExtWayland::xdg_toplevel`.
 - Add ability to make non-activating window on macOS using `NSPanel` with `NSWindowStyleMask::NonactivatingPanel`.
 - On Windows, add `IconExtWindows::from_resource_name`.
 - Implement `MonitorHandleProvider` for `MonitorHandle` to access common monitor API.

src/platform/wayland.rs

@@ -13,7 +13,12 @@
 //! * `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::platform_impl::wayland::Window;
 pub use crate::window::Theme;
 use crate::window::{Window as CoreWindow, WindowAttributes};
 
@@ -72,9 +77,17 @@ impl EventLoopBuilderExtWayland for EventLoopBuilder {
 /// Additional methods on [`Window`] that are specific to Wayland.
 ///
 /// [`Window`]: crate::window::Window
-pub trait WindowExtWayland {}
+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 dyn CoreWindow + '_ {}
+impl WindowExtWayland for dyn CoreWindow + '_ {
+    #[inline]
+    fn xdg_toplevel(&self) -> Option<NonNull<c_void>> {
+        self.cast_ref::<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};
 
@@ -214,6 +216,10 @@ 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 {