Add cursor hittest window functionality

CHANGELOG.md

@@ -8,10 +8,11 @@ And please only add new entries to the top of this list, right below the `# Unre
 
 # Unreleased
 
+- On macOS, Windows, and Wayland, add `set_cursor_hittest` to let the window ignore mouse events.
 - On Windows, added `WindowExtWindows::set_skip_taskbar` and `WindowBuilderExtWindows::with_skip_taskbar`.
 - On Windows, added `EventLoopBuilderExtWindows::with_msg_hook`.
 - On Windows, remove internally unique DC per window.
-- macOS: Remove the need to call `set_ime_position` after moving the window.
+- On macOS, remove the need to call `set_ime_position` after moving the window.
 - Added `Window::is_visible`.
 - Added `Window::is_resizable`.
 - Added `Window::is_decorated`.

FEATURES.md

@@ -102,6 +102,7 @@ If your PR makes notable changes to Winit's features, please update this section
 - **Mouse set location**: Forcibly changing the location of the pointer.
 - **Cursor grab**: Locking the cursor so it cannot exit the client area of a window.
 - **Cursor icon**: Changing the cursor icon, or hiding the cursor.
+- **Cursor hittest**: Handle or ignore mouse events for a window.
 - **Touch events**: Single-touch events.
 - **Touch pressure**: Touch events contain information about the amount of force being applied.
 - **Multitouch**: Multi-touch events, including cancellation of a gesture.
@@ -199,6 +200,7 @@ Legend:
 |Mouse set location      |✔️       |✔️      |✔️       |❓           |**N/A**|**N/A**|**N/A**|
 |Cursor grab             |✔️       |▢[#165] |▢[#242]  |✔️         |**N/A**|**N/A**|✔️        |
 |Cursor icon             |✔️       |✔️      |✔️       |✔️           |**N/A**|**N/A**|✔️        |
+|Cursor hittest          |✔️       |✔️      |❌       |✔️           |**N/A**|**N/A**|❌        |
 |Touch events            |✔️       |❌      |✔️       |✔️          |✔️    |✔️     |❌        |
 |Touch pressure          |✔️       |❌      |❌       |❌          |❌    |✔️     |❌        |
 |Multitouch              |✔️       |❌      |✔️       |✔️          |✔️    |✔️     |❌        |

src/platform_impl/android/mod.rs

@@ -774,6 +774,12 @@ impl Window {
         ))
     }
 
+    pub fn set_cursor_hittest(&self, _hittest: bool) -> Result<(), error::ExternalError> {
+        Err(error::ExternalError::NotSupported(
+            error::NotSupportedError::new(),
+        ))
+    }
+
     pub fn raw_window_handle(&self) -> RawWindowHandle {
         let mut handle = AndroidNdkHandle::empty();
         if let Some(native_window) = ndk_glue::native_window().as_ref() {

src/platform_impl/ios/window.rs

@@ -196,6 +196,10 @@ impl Inner {
         Err(ExternalError::NotSupported(NotSupportedError::new()))
     }
 
+    pub fn set_cursor_hittest(&self, _hittest: bool) -> Result<(), ExternalError> {
+        Err(ExternalError::NotSupported(NotSupportedError::new()))
+    }
+
     pub fn set_minimized(&self, _minimized: bool) {
         warn!("`Window::set_minimized` is ignored on iOS")
     }

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

src/platform_impl/macos/util/async.rs

@@ -10,7 +10,7 @@ use cocoa::{
 };
 use dispatch::Queue;
 use objc::rc::autoreleasepool;
-use objc::runtime::{BOOL, NO};
+use objc::runtime::{BOOL, NO, YES};
 
 use crate::{
     dpi::LogicalSize,
@@ -93,6 +93,14 @@ pub unsafe fn set_level_async(ns_window: id, level: ffi::NSWindowLevel) {
     });
 }
 
+// `setIgnoresMouseEvents_:` isn't thread-safe, and fails silently.
+pub unsafe fn set_ignore_mouse_events(ns_window: id, ignore: bool) {
+    let ns_window = MainThreadSafe(ns_window);
+    Queue::main().exec_async(move || {
+        ns_window.setIgnoresMouseEvents_(if ignore { YES } else { NO });
+    });
+}
+
 // `toggleFullScreen` is thread-safe, but our additional logic to account for
 // window styles isn't.
 pub unsafe fn toggle_full_screen_async(

src/platform_impl/macos/window.rs

@@ -678,6 +678,15 @@ impl UnownedWindow {
         Ok(())
     }
 
+    #[inline]
+    pub fn set_cursor_hittest(&self, hittest: bool) -> Result<(), ExternalError> {
+        unsafe {
+            util::set_ignore_mouse_events(*self.ns_window, !hittest);
+        }
+
+        Ok(())
+    }
+
     pub(crate) fn is_zoomed(&self) -> bool {
         // because `isZoomed` doesn't work if the window's borderless,
         // we make it resizable temporalily.

src/platform_impl/web/window.rs

@@ -239,6 +239,11 @@ impl Window {
         Err(ExternalError::NotSupported(NotSupportedError::new()))
     }
 
+    #[inline]
+    pub fn set_cursor_hittest(&self, _hittest: bool) -> Result<(), ExternalError> {
+        Err(ExternalError::NotSupported(NotSupportedError::new()))
+    }
+
     #[inline]
     pub fn set_minimized(&self, _minimized: bool) {
         // Intentionally a no-op, as canvases cannot be 'minimized'

src/platform_impl/windows/window.rs

@@ -361,6 +361,19 @@ impl Window {
         Ok(())
     }
 
+    #[inline]
+    pub fn set_cursor_hittest(&self, hittest: bool) -> Result<(), ExternalError> {
+        let window = self.window.clone();
+        let window_state = Arc::clone(&self.window_state);
+        self.thread_executor.execute_in_thread(move || {
+            WindowState::set_window_flags(window_state.lock(), window.0, |f| {
+                f.set(WindowFlags::IGNORE_CURSOR_EVENT, !hittest)
+            });
+        });
+
+        Ok(())
+    }
+
     #[inline]
     pub fn id(&self) -> WindowId {
         WindowId(self.hwnd())

src/platform_impl/windows/window_state.rs

@@ -15,10 +15,10 @@ use windows_sys::Win32::{
         HWND_NOTOPMOST, HWND_TOPMOST, SWP_ASYNCWINDOWPOS, SWP_FRAMECHANGED, SWP_NOACTIVATE,
         SWP_NOMOVE, SWP_NOSIZE, SWP_NOZORDER, SW_HIDE, SW_MAXIMIZE, SW_MINIMIZE, SW_RESTORE,
         SW_SHOW, WINDOWPLACEMENT, WINDOW_EX_STYLE, WINDOW_STYLE, WS_BORDER, WS_CAPTION, WS_CHILD,
-        WS_CLIPCHILDREN, WS_CLIPSIBLINGS, WS_EX_ACCEPTFILES, WS_EX_APPWINDOW, WS_EX_LEFT,
-        WS_EX_NOREDIRECTIONBITMAP, WS_EX_TOPMOST, WS_EX_WINDOWEDGE, WS_MAXIMIZE, WS_MAXIMIZEBOX,
-        WS_MINIMIZE, WS_MINIMIZEBOX, WS_OVERLAPPED, WS_OVERLAPPEDWINDOW, WS_POPUP, WS_SIZEBOX,
-        WS_SYSMENU, WS_VISIBLE,
+        WS_CLIPCHILDREN, WS_CLIPSIBLINGS, WS_EX_ACCEPTFILES, WS_EX_APPWINDOW, WS_EX_LAYERED,
+        WS_EX_LEFT, WS_EX_NOREDIRECTIONBITMAP, WS_EX_TOPMOST, WS_EX_TRANSPARENT, WS_EX_WINDOWEDGE,
+        WS_MAXIMIZE, WS_MAXIMIZEBOX, WS_MINIMIZE, WS_MINIMIZEBOX, WS_OVERLAPPED,
+        WS_OVERLAPPEDWINDOW, WS_POPUP, WS_SIZEBOX, WS_SYSMENU, WS_VISIBLE,
     },
 };
 
@@ -93,6 +93,8 @@ bitflags! {
 
         const MINIMIZED = 1 << 12;
 
+        const IGNORE_CURSOR_EVENT = 1 << 14;
+
         const EXCLUSIVE_FULLSCREEN_OR_MASK = WindowFlags::ALWAYS_ON_TOP.bits;
         const NO_DECORATIONS_AND_MASK = !WindowFlags::RESIZABLE.bits;
         const INVISIBLE_AND_MASK = !WindowFlags::MAXIMIZED.bits;
@@ -228,6 +230,9 @@ impl WindowFlags {
         if self.contains(WindowFlags::MAXIMIZED) {
             style |= WS_MAXIMIZE;
         }
+        if self.contains(WindowFlags::IGNORE_CURSOR_EVENT) {
+            style_ex |= WS_EX_TRANSPARENT | WS_EX_LAYERED;
+        }
 
         style |= WS_CLIPSIBLINGS | WS_CLIPCHILDREN | WS_SYSMENU;
         style_ex |= WS_EX_ACCEPTFILES;

src/window.rs

@@ -949,6 +949,19 @@ impl Window {
     pub fn drag_window(&self) -> Result<(), ExternalError> {
         self.window.drag_window()
     }
+
+    /// Modifies whether the window catches cursor events.
+    ///
+    /// If `true`, the window will catch the cursor events. If `false`, events are passed through
+    /// the window such that any other window behind it receives them. By default hittest is enabled.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS / Android / Web / X11:** Always returns an [`ExternalError::NotSupported`].
+    #[inline]
+    pub fn set_cursor_hittest(&self, hittest: bool) -> Result<(), ExternalError> {
+        self.window.set_cursor_hittest(hittest)
+    }
 }
 
 /// Monitor info functions.