On X11 and Wayland, add is_maximized support

Fixes #1845.

Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

CHANGELOG.md

@@ -3,6 +3,7 @@
 - On Android, implement `Window::request_redraw`
 - **Breaking:** On Web, remove the `stdweb` backend.
 - Added `Window::focus_window`to bring the window to the front and set input focus.
+- On Wayland and X11, implement `is_maximized` method on `Window`.
 
 # 0.25.0 (2021-05-15)
 

src/platform_impl/linux/mod.rs

@@ -380,8 +380,7 @@ impl Window {
 
     #[inline]
     pub fn is_maximized(&self) -> bool {
-        // TODO: Not implemented
-        false
+        x11_or_wayland!(match self; Window(w) => w.is_maximized())
     }
 
     #[inline]

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

@@ -54,6 +54,9 @@ pub struct Window {
     /// Fullscreen state.
     fullscreen: Arc<AtomicBool>,
 
+    /// Maximized state.
+    maximized: Arc<AtomicBool>,
+
     /// Available windowing features.
     windowing_features: WindowingFeatures,
 
@@ -87,6 +90,8 @@ impl Window {
         let scale_factor = sctk::get_surface_scale_factor(&surface);
 
         let window_id = super::make_wid(&surface);
+        let maximized = Arc::new(AtomicBool::new(false));
+        let maximzied_clone = maximized.clone();
         let fullscreen = Arc::new(AtomicBool::new(false));
         let fullscreen_clone = fullscreen.clone();
 
@@ -113,6 +118,8 @@ impl Window {
                             window_update.refresh_frame = true;
                         }
                         Event::Configure { new_size, states } => {
+                            let is_maximized = states.contains(&State::Maximized);
+                            maximzied_clone.store(is_maximized, Ordering::Relaxed);
                             let is_fullscreen = states.contains(&State::Fullscreen);
                             fullscreen_clone.store(is_fullscreen, Ordering::Relaxed);
 
@@ -235,6 +242,7 @@ impl Window {
             window_requests,
             event_loop_awakener: event_loop_window_target.event_loop_awakener.clone(),
             fullscreen,
+            maximized,
             windowing_features,
         };
 
@@ -368,6 +376,11 @@ impl Window {
         self.event_loop_awakener.ping();
     }
 
+    #[inline]
+    pub fn is_maximized(&self) -> bool {
+        self.maximized.load(Ordering::Relaxed)
+    }
+
     #[inline]
     pub fn set_maximized(&self, maximized: bool) {
         let maximize_request = WindowRequest::Maximize(maximized);

src/platform_impl/linux/x11/window.rs

@@ -779,6 +779,30 @@ impl UnownedWindow {
             .expect("Failed to change window minimization");
     }
 
+    #[inline]
+    pub fn is_maximized(&self) -> bool {
+        let state_atom = unsafe { self.xconn.get_atom_unchecked(b"_NET_WM_STATE\0") };
+        let state = self
+            .xconn
+            .get_property(self.xwindow, state_atom, ffi::XA_ATOM);
+        let horz_atom = unsafe {
+            self.xconn
+                .get_atom_unchecked(b"_NET_WM_STATE_MAXIMIZED_HORZ\0")
+        };
+        let vert_atom = unsafe {
+            self.xconn
+                .get_atom_unchecked(b"_NET_WM_STATE_MAXIMIZED_VERT\0")
+        };
+        match state {
+            Ok(atoms) => {
+                let horz_maximized = atoms.iter().any(|atom: &ffi::Atom| *atom == horz_atom);
+                let vert_maximized = atoms.iter().any(|atom: &ffi::Atom| *atom == vert_atom);
+                horz_maximized && vert_maximized
+            }
+            _ => false,
+        }
+    }
+
     fn set_maximized_inner(&self, maximized: bool) -> util::Flusher<'_> {
         let horz_atom = unsafe {
             self.xconn