Add cursor hittest window functionality (#2232)

Co-authored-by: z4122 <412213484@qq.com>
Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

src/platform_impl/linux/mod.rs

@@ -396,6 +396,11 @@ impl Window {
         x11_or_wayland!(match self; Window(window) => window.drag_window())
     }
 
+    #[inline]
+    pub fn set_cursor_hittest(&self, hittest: bool) -> Result<(), ExternalError> {
+        x11_or_wayland!(match self; Window(w) => w.set_cursor_hittest(hittest))
+    }
+
     #[inline]
     pub fn scale_factor(&self) -> f64 {
         x11_or_wayland!(match self; Window(w) => w.scale_factor() as f64)

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

@@ -482,6 +482,13 @@ impl Window {
         Ok(())
     }
 
+    #[inline]
+    pub fn set_cursor_hittest(&self, hittest: bool) -> Result<(), ExternalError> {
+        self.send_request(WindowRequest::PassthroughMouseInput(!hittest));
+
+        Ok(())
+    }
+
     #[inline]
     pub fn set_ime_position(&self, position: Position) {
         let scale_factor = self.scale_factor() as f64;

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

@@ -1,6 +1,7 @@
 use std::cell::Cell;
 use std::sync::{Arc, Mutex};
 
+use sctk::reexports::client::protocol::wl_compositor::WlCompositor;
 use sctk::reexports::client::protocol::wl_output::WlOutput;
 use sctk::reexports::client::Attached;
 use sctk::reexports::protocols::staging::xdg_activation::v1::client::xdg_activation_token_v1;
@@ -75,6 +76,9 @@ pub enum WindowRequest {
     /// `None` unsets the attention request.
     Attention(Option<UserAttentionType>),
 
+    /// Passthrough mouse input to underlying windows.
+    PassthroughMouseInput(bool),
+
     /// Redraw was requested.
     Redraw,
 
@@ -167,6 +171,9 @@ pub struct WindowHandle {
 
     /// Indicator whether user attention is requested.
     attention_requested: Cell<bool>,
+
+    /// Compositor
+    compositor: Attached<WlCompositor>,
 }
 
 impl WindowHandle {
@@ -177,6 +184,9 @@ impl WindowHandle {
         pending_window_requests: Arc<Mutex<Vec<WindowRequest>>>,
     ) -> Self {
         let xdg_activation = env.get_global::<XdgActivationV1>();
+        // Unwrap is safe, since we can't create window without compositor anyway and won't be
+        // here.
+        let compositor = env.get_global::<WlCompositor>().unwrap();
 
         Self {
             window,
@@ -189,6 +199,7 @@ impl WindowHandle {
             text_inputs: Vec::new(),
             xdg_activation,
             attention_requested: Cell::new(false),
+            compositor,
         }
     }
 
@@ -304,6 +315,20 @@ impl WindowHandle {
         }
     }
 
+    pub fn passthrough_mouse_input(&self, passthrough_mouse_input: bool) {
+        if passthrough_mouse_input {
+            let region = self.compositor.create_region();
+            region.add(0, 0, 0, 0);
+            self.window
+                .surface()
+                .set_input_region(Some(&region.detach()));
+            region.destroy();
+        } else {
+            // Using `None` results in the entire window being clickable.
+            self.window.surface().set_input_region(None);
+        }
+    }
+
     pub fn set_cursor_visible(&self, visible: bool) {
         self.cursor_visible.replace(visible);
         let cursor_icon = match visible {
@@ -425,6 +450,12 @@ pub fn handle_window_requests(winit_state: &mut WinitState) {
                     let window_update = window_updates.get_mut(window_id).unwrap();
                     window_update.refresh_frame = true;
                 }
+                WindowRequest::PassthroughMouseInput(passthrough) => {
+                    window_handle.passthrough_mouse_input(passthrough);
+
+                    let window_update = window_updates.get_mut(window_id).unwrap();
+                    window_update.refresh_frame = true;
+                }
                 WindowRequest::Attention(request_type) => {
                     window_handle.set_user_attention(request_type);
                 }

src/platform_impl/linux/x11/window.rs

@@ -1358,6 +1358,11 @@ impl UnownedWindow {
         self.set_cursor_position_physical(x, y)
     }
 
+    #[inline]
+    pub fn set_cursor_hittest(&self, _hittest: bool) -> Result<(), ExternalError> {
+        Err(ExternalError::NotSupported(NotSupportedError::new()))
+    }
+
     pub fn drag_window(&self) -> Result<(), ExternalError> {
         let pointer = self
             .xconn