On Wayland, handle none decorations

During the migration some logic wrt `none` decorations was lost along
the way, however we also now try to ask for client side decorations if
the user wants to disable server side decorations.

Fixes rust-windowing#2902.

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

@@ -105,11 +105,18 @@ impl Window {
             .map(|size| size.to_logical::<u32>(1.))
             .unwrap_or((800, 600).into());
 
-        let window = state.xdg_shell.create_window(
-            surface.clone(),
-            WindowDecorations::ServerDefault,
-            &queue_handle,
-        );
+        // We prefer server side decorations, however to not have decorations we ask for client
+        // side decorations instead.
+        let default_decorations = if attributes.decorations {
+            WindowDecorations::RequestServer
+        } else {
+            WindowDecorations::RequestClient
+        };
+
+        let window =
+            state
+                .xdg_shell
+                .create_window(surface.clone(), default_decorations, &queue_handle);
 
         let mut window_state = WindowState::new(
             event_loop_window_target.connection.clone(),
@@ -123,6 +130,9 @@ impl Window {
         // Set transparency hint.
         window_state.set_transparent(attributes.transparent);
 
+        // Set the decorations hint.
+        window_state.set_decorate(attributes.decorations);
+
         // Set the app_id.
         if let Some(name) = platform_attributes.name.map(|name| name.general) {
             window.set_app_id(name);

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

@@ -113,6 +113,9 @@ pub struct WindowState {
     /// Whether the CSD fail to create, so we don't try to create them on each iteration.
     csd_fails: bool,
 
+    /// Whether we should decorate the frame.
+    decorate: bool,
+
     /// Min size.
     min_inner_size: LogicalSize<u32>,
     max_inner_size: Option<LogicalSize<u32>>,
@@ -180,8 +183,8 @@ impl WindowState {
             ) {
                 Ok(mut frame) => {
                     frame.set_title(&self.title);
-                    // Ensure that the frame is not hidden.
-                    frame.set_hidden(false);
+                    // Hide the frame if we were asked to not decorate.
+                    frame.set_hidden(!self.decorate);
                     self.frame = Some(frame);
                 }
                 Err(err) => {
@@ -391,6 +394,7 @@ impl WindowState {
             connection,
             theme,
             csd_fails: false,
+            decorate: true,
             cursor_grab_mode: GrabState::new(),
             cursor_icon: CursorIcon::Default,
             cursor_visible: true,
@@ -706,6 +710,28 @@ impl WindowState {
     /// Whether show or hide client side decorations.
     #[inline]
     pub fn set_decorate(&mut self, decorate: bool) {
+        if decorate == self.decorate {
+            return;
+        }
+
+        self.decorate = decorate;
+
+        match self
+            .last_configure
+            .as_ref()
+            .map(|configure| configure.decoration_mode)
+        {
+            Some(DecorationMode::Server) if !self.decorate => {
+                // To disable decorations we should request client and hide the frame.
+                self.window
+                    .request_decoration_mode(Some(DecorationMode::Client))
+            }
+            _ if self.decorate => self
+                .window
+                .request_decoration_mode(Some(DecorationMode::Server)),
+            _ => (),
+        }
+
         if let Some(frame) = self.frame.as_mut() {
             frame.set_hidden(!decorate);
             // Force the resize.