gpui: Implement hover for Windows (#20894)

crates/gpui/src/platform/windows/events.rs

@@ -7,6 +7,7 @@ use windows::Win32::{
     Graphics::Gdi::*,
     System::SystemServices::*,
     UI::{
+        Controls::*,
         HiDpi::*,
         Input::{Ime::*, KeyboardAndMouse::*},
         WindowsAndMessaging::*,
@@ -43,7 +44,8 @@ pub(crate) fn handle_msg(
         WM_PAINT => handle_paint_msg(handle, state_ptr),
         WM_CLOSE => handle_close_msg(state_ptr),
         WM_DESTROY => handle_destroy_msg(handle, state_ptr),
-        WM_MOUSEMOVE => handle_mouse_move_msg(lparam, wparam, state_ptr),
+        WM_MOUSEMOVE => handle_mouse_move_msg(handle, lparam, wparam, state_ptr),
+        WM_MOUSELEAVE => handle_mouse_leave_msg(state_ptr),
         WM_NCMOUSEMOVE => handle_nc_mouse_move_msg(handle, lparam, state_ptr),
         WM_NCLBUTTONDOWN => {
             handle_nc_mouse_down_msg(handle, MouseButton::Left, wparam, lparam, state_ptr)
@@ -234,10 +236,32 @@ fn handle_destroy_msg(handle: HWND, state_ptr: Rc<WindowsWindowStatePtr>) -> Opt
 }
 
 fn handle_mouse_move_msg(
+    handle: HWND,
     lparam: LPARAM,
     wparam: WPARAM,
     state_ptr: Rc<WindowsWindowStatePtr>,
 ) -> Option<isize> {
+    let mut lock = state_ptr.state.borrow_mut();
+    if !lock.hovered {
+        lock.hovered = true;
+        unsafe {
+            TrackMouseEvent(&mut TRACKMOUSEEVENT {
+                cbSize: std::mem::size_of::<TRACKMOUSEEVENT>() as u32,
+                dwFlags: TME_LEAVE,
+                hwndTrack: handle,
+                dwHoverTime: HOVER_DEFAULT,
+            })
+            .log_err()
+        };
+        if let Some(mut callback) = lock.callbacks.hovered_status_change.take() {
+            drop(lock);
+            callback(true);
+            state_ptr.state.borrow_mut().callbacks.hovered_status_change = Some(callback);
+        }
+    } else {
+        drop(lock);
+    }
+
     let mut lock = state_ptr.state.borrow_mut();
     if let Some(mut callback) = lock.callbacks.input.take() {
         let scale_factor = lock.scale_factor;
@@ -272,6 +296,18 @@ fn handle_mouse_move_msg(
     Some(1)
 }
 
+fn handle_mouse_leave_msg(state_ptr: Rc<WindowsWindowStatePtr>) -> Option<isize> {
+    let mut lock = state_ptr.state.borrow_mut();
+    lock.hovered = false;
+    if let Some(mut callback) = lock.callbacks.hovered_status_change.take() {
+        drop(lock);
+        callback(false);
+        state_ptr.state.borrow_mut().callbacks.hovered_status_change = Some(callback);
+    }
+
+    Some(0)
+}
+
 fn handle_syskeydown_msg(
     wparam: WPARAM,
     lparam: LPARAM,

crates/gpui/src/platform/windows/window.rs

@@ -42,6 +42,7 @@ pub struct WindowsWindowState {
     pub callbacks: Callbacks,
     pub input_handler: Option<PlatformInputHandler>,
     pub system_key_handled: bool,
+    pub hovered: bool,
 
     pub renderer: BladeRenderer,
 
@@ -95,6 +96,7 @@ impl WindowsWindowState {
         let callbacks = Callbacks::default();
         let input_handler = None;
         let system_key_handled = false;
+        let hovered = false;
         let click_state = ClickState::new();
         let system_settings = WindowsSystemSettings::new(display);
         let nc_button_pressed = None;
@@ -110,6 +112,7 @@ impl WindowsWindowState {
             callbacks,
             input_handler,
             system_key_handled,
+            hovered,
             renderer,
             click_state,
             system_settings,
@@ -326,6 +329,7 @@ pub(crate) struct Callbacks {
     pub(crate) request_frame: Option<Box<dyn FnMut(RequestFrameOptions)>>,
     pub(crate) input: Option<Box<dyn FnMut(crate::PlatformInput) -> DispatchEventResult>>,
     pub(crate) active_status_change: Option<Box<dyn FnMut(bool)>>,
+    pub(crate) hovered_status_change: Option<Box<dyn FnMut(bool)>>,
     pub(crate) resize: Option<Box<dyn FnMut(Size<Pixels>, f32)>>,
     pub(crate) moved: Option<Box<dyn FnMut()>>,
     pub(crate) should_close: Option<Box<dyn FnMut() -> bool>>,
@@ -635,9 +639,8 @@ impl PlatformWindow for WindowsWindow {
         self.0.hwnd == unsafe { GetActiveWindow() }
     }
 
-    // is_hovered is unused on Windows. See WindowContext::is_window_hovered.
     fn is_hovered(&self) -> bool {
-        false
+        self.0.state.borrow().hovered
     }
 
     fn set_title(&mut self, title: &str) {
@@ -728,7 +731,9 @@ impl PlatformWindow for WindowsWindow {
         self.0.state.borrow_mut().callbacks.active_status_change = Some(callback);
     }
 
-    fn on_hover_status_change(&self, _: Box<dyn FnMut(bool)>) {}
+    fn on_hover_status_change(&self, callback: Box<dyn FnMut(bool)>) {
+        self.0.state.borrow_mut().callbacks.hovered_status_change = Some(callback);
+    }
 
     fn on_resize(&self, callback: Box<dyn FnMut(Size<Pixels>, f32)>) {
         self.0.state.borrow_mut().callbacks.resize = Some(callback);

crates/gpui/src/window.rs

@@ -1241,7 +1241,11 @@ impl<'a> WindowContext<'a> {
     /// that currently owns the mouse cursor.
     /// On mac, this is equivalent to `is_window_active`.
     pub fn is_window_hovered(&self) -> bool {
-        if cfg!(any(target_os = "linux", target_os = "freebsd")) {
+        if cfg!(any(
+            target_os = "windows",
+            target_os = "linux",
+            target_os = "freebsd"
+        )) {
             self.window.hovered.get()
         } else {
             self.is_window_active()