wayland: add prefer_csd attribute

winit-wayland/src/lib.rs

@@ -98,6 +98,7 @@ pub(crate) struct ApplicationName {
 pub struct WindowAttributesWayland {
     pub(crate) name: Option<ApplicationName>,
     pub(crate) activation_token: Option<ActivationToken>,
+    pub(crate) prefer_csd: bool,
 }
 
 impl WindowAttributesWayland {
@@ -119,6 +120,18 @@ impl WindowAttributesWayland {
         self.activation_token = Some(token);
         self
     }
+
+    /// Builds the window with a given preference for client-side decorations.
+    ///
+    /// When set to `true`, the window will tell the compositor that it prefers
+    /// client-side decorations, even if server-side decorations are available.
+    /// When set to `false` (the default), the window will indicate a preference
+    /// for server-side decorations.
+    #[inline]
+    pub fn with_prefer_csd(mut self, prefer_csd: bool) -> Self {
+        self.prefer_csd = prefer_csd;
+        self
+    }
 }
 
 impl PlatformWindowAttributes for WindowAttributesWayland {

winit-wayland/src/window/mod.rs

@@ -106,6 +106,12 @@ impl Window {
         let window =
             state.xdg_shell.create_window(surface.clone(), default_decorations, &queue_handle);
 
+        let WindowAttributesWayland { name: app_name, activation_token, prefer_csd } = *attributes
+            .platform
+            .take()
+            .and_then(|p| p.cast::<WindowAttributesWayland>().ok())
+            .unwrap_or_default();
+
         let mut window_state = WindowState::new(
             event_loop_window_target.handle.clone(),
             &event_loop_window_target.queue_handle,
@@ -113,6 +119,7 @@ impl Window {
             size,
             window.clone(),
             attributes.preferred_theme,
+            prefer_csd,
         );
 
         window_state.set_window_icon(attributes.window_icon);
@@ -125,13 +132,6 @@ impl Window {
         // Set the decorations hint.
         window_state.set_decorate(attributes.decorations);
 
-        let (app_name, activation_token) =
-            match attributes.platform.take().and_then(|p| p.cast::<WindowAttributesWayland>().ok())
-            {
-                Some(attrs) => (attrs.name, attrs.activation_token),
-                None => (None, None),
-            };
-
         // Set the app_id.
         if let Some(name) = app_name.map(|name| name.general) {
             window.set_app_id(name);

winit-wayland/src/window/state.rs

@@ -134,6 +134,9 @@ pub struct WindowState {
     /// Whether we should decorate the frame.
     decorate: bool,
 
+    /// Whether we should tell the compositor that we prefer drawing decorations ourself.
+    prefer_csd: bool,
+
     /// Min size.
     min_surface_size: LogicalSize<u32>,
     max_surface_size: Option<LogicalSize<u32>>,
@@ -180,6 +183,7 @@ impl WindowState {
         initial_size: Size,
         window: Window,
         theme: Option<Theme>,
+        prefer_csd: bool,
     ) -> Self {
         let compositor = winit_state.compositor_state.clone();
         let pointer_constraints = winit_state.pointer_constraints.clone();
@@ -209,6 +213,7 @@ impl WindowState {
             selected_cursor: Default::default(),
             cursor_visible: true,
             decorate: true,
+            prefer_csd,
             fractional_scale,
             frame: None,
             frame_callback_state: FrameCallbackState::None,
@@ -955,7 +960,7 @@ impl WindowState {
     /// Whether show or hide client side decorations.
     #[inline]
     pub fn set_decorate(&mut self, decorate: bool) {
-        if decorate == self.decorate {
+        if decorate == self.decorate && !self.prefer_csd {
             return;
         }
 
@@ -966,6 +971,9 @@ impl WindowState {
                 // To disable decorations we should request client and hide the frame.
                 self.window.request_decoration_mode(Some(DecorationMode::Client))
             },
+            _ if self.decorate && self.prefer_csd => {
+                self.window.request_decoration_mode(Some(DecorationMode::Client))
+            },
             _ if self.decorate => self.window.request_decoration_mode(Some(DecorationMode::Server)),
             _ => (),
         }